ovinge lauren thesis - ttu-ir.tdl.org

The use of alternative feeding strategies to improve feedlot beef cattle growth performance and nutrient utilization

by

Lauren A. Ovinge, B.S.

A Thesis

In

Animal Science

Submitted to the Graduate Faculty Of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCES

Approved

Jhones O. Sarturi Chair of Committee

Michael A. Ballou

Sara J. Trojan

Mark A. Sheridan Dean of the Graduate School

August, 2016

TexasTechUniversity,LaurenAOvinge,August2016

ii

ACKNOWLEDGEMENTS

Firstand foremost Iwould like to thankmyparents forsupporting

methroughthisjourneyandprovidingmewithtwogreatexamplesinwhich

to follow. Your support, love and encouragement have been greatly

appreciatedthroughoutmyuniversitycareer. Iwouldalso liketothankmy

threebrothersandmyboyfriend;yourconversationswerealwaysawelcome

distraction. Secondly, the success you have all enjoyed in your respective

fieldsthroughhardworkanddedicationhashelpedtogivememotivationto

succeedinmine.

IwouldalsoliketothankDr.JhonesSarturiforspendingthelasttwo

years working with and mentoring me. Your knowledge and wisdom has

helpedmeturnfromsomeonewithaninterest infeedlotnutritionintoone

withapassionforfeedlotnutrition.Youhavegivenmeasolidfoundationon

whichtobuildmyfuturecareeraswellashowtolivemylife.

Iwould also like to thank the othermembers onmy committee,Dr.

Trojanfortakingthetimetowritemereferencelettersandaboutthefeedlot

industry, and Dr. Ballou for taking the time to involve us and teach us

statistics. I would also like to thank the students here at Texas Tech,

specifically those in our lab group that helpedme through experiments no

matterwhatwasgoingon.ThesupportfromPedroCampanili,LucasPellarin,

andBarbaraLemosespeciallyhelpedmegetthroughthis.Finally,theother

friendsI’vemadehereaswellasthosebackinCanadaisgreatlyappreciated,

yourinsightsintobeefproductionhavehelpedmetogrowandlearn.


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TABLE OF CONTENTS

ACKNOWLEDGEMENTS.............................................................................................ii

ABSTRACT....................................................................................................................vi

LISTOFTABLES..........................................................................................................ix

LISTOFFIGURES........................................................................................................xi

I.LITERATUREREVIEW.............................................................................................1NaturalProgramBeefSteerProductionMethods...................................................1

Introduction.........................................................................................................................1

ConventionalandNonconventionalBeefProduction............................................3

Direct-FedMicrobials........................................................................................................4

Probiotics......................................................................................................................................6Yeast................................................................................................................................................6

MechanismsofAction.......................................................................................................7

LacticAcidUtilization..............................................................................................................9FiberDigestibility....................................................................................................................10AmmoniaUptake......................................................................................................................11

Supplementation..............................................................................................................12

Levels............................................................................................................................................12Activity..........................................................................................................................................13DietDigestibility.......................................................................................................................14Health............................................................................................................................................15GrowthPerformance..............................................................................................................17CarcassCharacteristics..........................................................................................................18Cost.................................................................................................................................................19Implications................................................................................................................................20

Conclusions.........................................................................................................................20

AdaptationofBeefFinishingSteerstoHighConcentrateFinishingDiets....23

Introduction.......................................................................................................................23

AdaptationPeriod............................................................................................................25

Methods........................................................................................................................................27Ingredients,TimeandSorting............................................................................................28

Health...................................................................................................................................30

Acidosis........................................................................................................................................30Bloat...............................................................................................................................................31

GrowthPerformanceandFeedIntake......................................................................33

RuminalBacterialCommunity.....................................................................................34


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CottonBurrs.......................................................................................................................36

Implications........................................................................................................................38

II.Effectofaliveyeastproductinafinishingfeedlotdietongrowth

performance,digestibility,andcarcasscharacteristicsinnatural

programfeedlotsteers...........................................................................................40Abstract................................................................................................................................40

Introduction.......................................................................................................................42

MaterialsandMethods...................................................................................................43

FeedlotGrowthPerformance...................................................................................................43ApparentTotalTractNutrientDigestibility......................................................................46LaboratorialAnalyses.................................................................................................................47FeedingBehavior..........................................................................................................................47StatisticalAnalyses.......................................................................................................................48

Results..................................................................................................................................48

TreatmentData..............................................................................................................................48GrowthPerformanceandCarcassCharacteristics.........................................................49ApparentTotalTractNutrientDigestibility......................................................................50

Discussion...........................................................................................................................51

Implications........................................................................................................................57

TablesandFigures...........................................................................................................59

III.CottonBurrsasanalternativeroughagesourcetoadaptbeefsteers

tosteam-flakedcornbasedfinisherdiets.......................................................67Abstract................................................................................................................................67

Introduction.......................................................................................................................69

MaterialsandMethods...................................................................................................70

Treatments,ExperimentalDesignandFeeding...............................................................70RuminalpH,VolatileFattyAcids,andAmmonia.............................................................71ApparentTotalTractNutrientDigestibility......................................................................72LabAnalyses....................................................................................................................................72RuminalInSituWheatHayDegradability..........................................................................73FeedingBehavior..........................................................................................................................74StatisticalAnalyses.......................................................................................................................75

Results..................................................................................................................................75

DryMatterIntake..........................................................................................................................75RuminalpH,VolatileFattyAcids,andAmmonia.............................................................76ApparentTotalTractNutrientDigestibility......................................................................78RuminalInSituWheatHayDegradability..........................................................................79FeedingBehavior..........................................................................................................................79


v

Discussion...........................................................................................................................80

Implications........................................................................................................................87

LiteratureCited.................................................................................................................89

TablesandFigures...........................................................................................................98


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ABSTRACT

The use of alternative feeding strategies such as yeast as a feed additive

and cotton burrs as a roughage source to improve feedlot beef cattle growth

performance and nutrient utilization were evaluated in two experiments. The first

experiment evaluated the effects of live yeast fed to natural program beef steers

and its effect on growth performance, apparent total tract nutrient digestibility,

carcass characteristics, and feeding behavior. In experiment 1, steers (n = 144;

341 ± 52 kg) were assigned to 1 of 3 treatments, Control (CTL), Low Yeast (LY),

and High Yeast (HY) in a completely randomized block design (12

pens/treatment). Data were analyzed using the GLIMMIX procedure of SAS, with

pen as experimental unit. Gain efficiency tended to be quadratically improved (P

= 0.08) between d0 and 183 with LY diet being 4.3% greater than other

treatments. The number of premium choice carcasses increased linearly (P < 0.01)

with increasing yeast levels at 33.3%, 68.8% and 70%, respectively. There was a

tendency (P = 0.09) for choice carcasses to be decreased linearly with increasing

yeast level. A quadratic response was observed for nutrient digestibility, in which

steers fed LY had improved digestibility (P < 0.01) of dry matter by 5.4%,

organic matter by 4.8%, neutral detergent fiber by 15.2%, acid detergent fiber by

20.2%, crude protein by 6.2%, and ether extract by 2.5% compared to HY and

CTL treatments. Moderate inclusion of live yeast improved efficiency of nutrient

utilization of steers fed steam-flaked corn-based finishing diets, which tended to

positively affect growth performance.


vii

The second study evaluated the effect of cotton burrs as a roughage source

during the transition of beef cattle (hay to finisher diet) on intake, ruminal

characteristics, apparent total tract nutrient digestibility, and feeding behavior.

Ruminally cannulated steers (n = 6; BW = 235 ± 81 kg) were assigned using a

complete randomized design to 1 of 2 adaptation strategies: alfalfa hay or cotton

burrs-based. Steers were fed ad libitum once daily, a series of six diets (7-d period

each): wheat hay; 4 step-ups; and a finisher. Ruminal fiber degradability, pH,

VFA and NH3, and apparent total tract nutrient digestibility were measured. Data

were analyzed using GLIMMIX procedure of SAS (wheat hay period used as

covariate). Intake was not affected by adaptation strategies (P ≥ 0.16), except for

a tendency (P = 0.10) for alfalfa-strategy steers to ruminate more per kg of NDF

consumed during finisher diet. Steers fed cotton burrs-strategy had a lower

ruminal pH average on step-3 and finisher periods (5.62 and 5.51 vs. 6.04 and

5.83; P < 0.01 and P = 0.05, respectively). A greater area of pH below 5.6 (200

vs. 15 min*pH; P < 0.01); lower ruminal NH3 concentration (5.1 vs. 8.8 mg/L; P

< 0.01); and lower digestibility (OM, ADF, and hemicellulose; P = 0.02) during

step-3 were also observed for steers fed cotton burrs-strategy versus alfalfa hay

strategy, respectively. However, cotton burrs-strategy steers showed greater (P <

0.01) NDF digestibility during step-4; greater (P < 0.01) OM digestibility during

finisher diet; and lower acetate/propionate ratio (P = 0.04) with a tendency (P =

0.08) to have greater propionate molar proportion during step-2. Ruminal fiber

degradability was not affected by adaptation strategies (P ≥ 0.36). Cotton burrs

adaptation strategy induced an improved ruminal fermentation environment


viii

during finisher diet, although with riskier ruminal pH and rumination than alfalfa-

strategy. Beef cattle diets can include a variety of products to effect growth

performance and nutrient utilization, which provides a benefit to beef cattle

producers.

Key words: adaptation, beef cattle, alternative feeds, cotton, yeast


ix

LIST OF TABLES

1. Dietaryingredientsandnutritionalcompositionofdietsfedtonaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.................................................................................................................59

2. EffectsofABVistayeast(Saccharomycescerevisiae)ongrowthperformanceofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................60

3. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcasscharacteristicsofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................61

4. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcassqualityofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................62

5. EffectsofABVistayeast(Saccharomycescerevisiae)onliverscoresofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................63

6. EffectsofABVistayeast(Saccharomycescerevisiae)onfeedingbehaviorofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................64

7. Dietarycompositionofadaptationdietsusingcottonburrsoralfalfahayasaroughagesource.........................................................................98

8. Analyzednutritionalcompositionofadaptationdietsusingcottonburrsoralfalfahayasaroughagesource..........................................99

9. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsondrymatterintake,ruminalparameters-WheatHay,Step1and2................................................................................................................100

10. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsondrymatterintake,ruminalparameters-Steps3and4,Finisher........................................................................................................................101

11. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonruminalvolatilefattyacidprofile-WheatHay,Step1and2..........102

12. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonruminalvolatilefattyacidprofile-Step3,4andFinisher................103


x

13. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonapparenttotaltractnutrientdigestibility-WheatHay,Step1and2................................................................................................................104

14. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonapparenttotaltractnutrientdigestibility-Step3and4,Finisher........................................................................................................................105

15. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminaldrymatterdegradability................................................106

16. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalorganicmatterdegradability........................................107

17. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalneutraldetergentfiberdegradability.......................108

18. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalaciddetergentfiberdegradability..............................109

19. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalhemicellulosedegradability..........................................110

20. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonfeedingbehavior-WheatHay,Step1and2............................................111

21. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonfeedingbehavior-Step3and4,Finisher.................................................112


xi

LIST OF FIGURES

1. EffectsofABVistayeast(Saccharomycescerevisiae)onapparenttotaltractnutrientdigestibilityofnaturalprogrambeefsteersfedsteam-flakedcorn-basedfinishingdiets...................................................65

2. EffectsofABVistayeast(Saccharomycescerevisiae)onapparentfiberfractiontotaltractnutrientdigestibilityofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet..........................66

3. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonaverageruminalpH..........................................................................................113

4. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonaverageammoniaconcentration(mg/L)...............................................114


1

CHAPTER I

REVIEW OF LITERATURE

Natural Program Beef Production Methods

Introduction

Current conventional production methods used by the beef cattle industry

have become targets of public scrutiny in recent years. This is specifically in

regards to growth promoting technologies and antibiotics, which improve feed

efficiency and prevent beef cattle illness (Nayga, 1996, Flint and Garner, 2009).

Some methods used to enhance cattle growth are ionophores, steroidal implants

and beta agonists. Ionophores alter the ruminal environment by shifting the

growth of microorganisms from gram-positive bacteria that produce methane to

gram-negative bacteria, improving gain efficiency (DiLorenzo and Galyean,

2010). Steroidal implants are inserted into the ear of cattle and release estrogenic

hormones over time to improve growth performance throughout the growing

phase (Preston et al., 1995). Another growth promoting technology is beta-

agonists; fed to cattle during the last 28-42 days in the feedlot to improve growth

performance and lean tissue accretion during the final growth phase (Loneragan et

al., 2014). Recent concern has been on the increasing rates of antibiotic resistance

in human medicine. Although many of the antibiotics used in feedlot production

are not related to human medicine, consumers are still apprehensive. As a result,

producers are being governed into practicing more judicious use of antibiotics.

Despite the conflict of ideas regarding production methods and technology use,

the production sector still relies on consumer demand to market their beef (Knight


2

and Warland, 2004). If consumer demands are not met, they could potentially

switch to other sources of protein, decreasing demand for beef. As the global

middle class is set to increase in the next few years and with it the amount of

disposable income available to afford animal protein sources grows, the beef

industry needs to work to keep beef at the center of the plate (Flint and Garner,

2009). Although growth-promoting technologies such as direct fed antimicrobials,

beta agonists, and steroidal implants improve growth performance and

sustainability of the beef cattle industry, public distrust is helping fuel an increase

in research of natural growth promoting technologies, such as yeast. This can be

viewed as an opportunity, and diversifying the beef cattle market may add a

premium producers need to improve profit margins.

Direct fed microbials (DFM) are used by the beef industry to improve

animal performance (McAllister et al., 2011, Robinson and Erasmus, 2009, Flint

and Garner, 2009), with the simultaneous intent to reduce reliance on sub-

therapeutic antibiotics in beef cattle diets. Direct fed microbials can be fed in

bacterial or fungal form, and can be administered to cattle either through a bolus

or mixed directly with the feed (McAllister et al., 2011, Ghorbani et al., 2002).

There has been inconsistent data about whether or not DFM in the diet improves

growth performance of beef cattle in the feedlot (Desnoyers, et al., 2009). This

has resulted in a need for research into how these products can improve nutrient

utilization in various feeding strategies. This will be a difficult task in diets that

are already highly digestible. Yeast is classified as a microbial growth factor

because it modifies the rumen environment to encourage cellulolytic bacterial


3

growth through a reduction in lactic acid production (Swyers et al., 2014). The

objective of this review was to observe the use of yeast in the diet of cattle and

view its impact on beef feedlot production.

Conventional and Nonconventional Production

Comparing conventional and natural program fed steers is one that is a

great challenge because many different products are available to both systems to

improve growth performance. Much research suggests natural program steers are

less efficient because they do not have access to growth promotants such as

ionophores, implants or beta agonists, and have greater incidences of liver

abscesses without access to sub-therapeutic antibiotics in the feed. As well as

reducing reliance on sub therapeutic antibiotics, steroidal implants and beta

agonists, natural feedlot diets generally include higher levels of roughage to

reduce the risk of digestive upsets and liver abscesses (Maxwell et al., 2014). In a

meta-analysis by Wileman et al. (2009), researchers evaluated implanted versus

non-implanted cattle, and those that received metaphylactic treatment on arrival

compared to those that did not. The difference between steers in conventional

versus nonconventional programs was improved ADG by 0.25 kg/d, increased

DMI by 0.53 kg/d, and improved G:F by a factor of 0.02. Unfortunately, models

such as this do not include the use of DFM and management strategies of the

cattle, so differences between programs are difficult to tell. Some natural

programs allow the use of ionophores to control for coccidiosis, which also

improves gain efficiency of cattle in natural programs (Wileman et al., 2009).

Another difference between natural and conventional programs is the morbidity


4

and mortality rate during the feedlot production system. Wileman et al. (2009)

noted cattle not fed tylosin in the diet had 30% liver abscesses, while those fed

tylosin had 8% liver abscesses. Capper et al. (2012) evaluated all systems in beef

production and determined that conventional production was the most efficient,

but also determined all production systems were sustainable and improving in

terms of production efficiency. Growth promoting technologies improve growth

performance of beef cattle, however, their social acceptability is becoming an

issue and more effective communication with consumers is necessary (Wileman

et al., 2009). Adding diversity to the beef industry benefits producers who desire

to improve the profitability of their operation (Maxwell et al., 2014). All

production systems may be viable options for producers and are dependent on

their customer, their values and the economics of such a decision.

Direct-Fed Microbials

A DFM is defined as “a source of live, naturally occurring

microorganisms” (Yoon and Stern, 1995). Products researched have been

methane inhibitors, propionate enhancers, and microbial growth factors (Yoon

and Stern, 1995). Probiotics are described by the FAO-WHO (2001) as “live

microorganisms which, when administered in adequate amounts, confer a health

benefit on the host” (FAO-WHO, 2001). The term DFM includes all microbial

cultures, extracts, and enzymes, which benefit the environment of the digestive

tract and animal health. The mechanisms of action of most DFM are not well

understood, due to the inconsistency of results and the wide variety of products

available (Krehbiel et al., 2003). Direct fed microbials can have multiple effects


5

on the animal ranging from improved nutrient digestibility to decreasing

morbidity (Yoon and Stern, 1995). The original intent of feeding DFM was to

improve the establishment of beneficial gut microbiota during stressful periods in

the ruminant’s life, such as introduction to the feedlot (Ghorbani et al., 2002).

Following further research, it was observed DFM might have the ability to

improve growth performance of the animal (Ghorbani et al., 2002).

The goal of ruminant nutritionists is to manipulate ruminal microbiota to

maximize utilization of the nutrients in the diet (Yoon and Stern, 1995). Ghorbani

et al. (2002) observed including DFM in feedlot diets decreased ruminal

amylolytic bacteria, which are responsible for starch degradation (Chaucheryas-

Durand et al., 2008). This results in a more desirable environment for cellulolytic

bacteria to grow and increasing fiber digestibility. Direct fed microbials may be

included as part of a feedlot finishing diet as a tool to combat the negative effects

of acidosis, improving beef cattle growth performance (Ghorbani et al., 2002).

Other uses for DFM include, preserving silages and haylages to provide a safe,

nutritious and viable ingredient for beef cattle diets (Yoon and Stern, 1995).

Considering the lack of knowledge concerning the gastrointestinal environment of

beef cattle, the use of DFM and understanding their modes of action is imperative

to help better understand the rumen environment and its role in digestion.

Inconsistent results between studies suggests more research is necessary to

observe the strains of yeast, different levels and their handling procedures are

needed to achieve improved results every time yeast is included in the diet.


6

Probiotics

Probiotics are a bacterial class of DFM used to improve growth

performance of beef cattle by developing the gastrointestinal tract environment.

The probiotics generally utilized are those that improve the growth of lactic acid

producing bacteria within the rumen. Some probiotics that have been fed to

ruminants are Propionibacterium and Enterococcus faecium (Ghorbani et al.,

2002). When cattle consume high concentrate diets, lactic acid is produced by

ruminal microbiota causing a reduction in the ruminal pH. These bacterial species

encourage the production of lactic acid before high concentrate diets are

introduced, because the rumen is better equipped to combat lactic acid when high

starch diets are consumed (Beauchemin et al., 2003). As a result, ruminal

microbiota adjust more efficiently to the influx of lactic acid, reducing acidosis

risk and any ensuing liver abscesses (Beauchemin, et al., 2003). These bacterial

species also have an effect on the rumen environment and help increase protozoal

numbers within the rumen (Ghorbani et al., 2002). Protozoa are responsible for

consuming starch and utilizing it at a later time, reducing acidosis risk by slowing

the digestion of starch (Ghorbani et al, 2002). Adding probiotics to the diet is

beneficial for ruminal fermentation variables by improving the ruminal

environment.

Yeast

Yeast products are a class of DFM used by the beef industry to modify the

rumen environment to improve cattle growth performance (Kung et al., 1997,

Yoon and Stern, 1995). Yeast generally comes in an active dry form (ADY),


7

which has been freeze-dried to preserve its activity. It can also be mixed with a

medium in which to ferment (Chaucheryas-Durand et al., 2008). Yeasts are not

currently regulated by the FDA, but have been placed on the Generally

Recognized as Safe list in North America. Due to the fact yeasts are not regulated,

their product quality may not always be consistent. However, most companies are

attempting to have the yeast products that are viable at greater than 10 billion

colony forming units (CFU) per gram (Chaucheryas-Durand et al., 2008). Yeasts

provide a natural alternative feedlot for systems to improve production without

depending on antibiotics. Yeasts have helped to improve dairy production and

growth performance in feedlot cattle (Chaucheryas-Durand et al., 2008).

Mechanisms of Action

One purpose of including yeast in the diet is to stabilize the rumen

environment when cattle are fed high-concentrate diets (Chaucheryas-Durand et

al., 2008, Vyas et al., 2014). In a review by Yoon and Stern, (1995), they reported

findings from as early as 1950, which attributed altered ruminal fermentation

patterns due to yeast included in the diet. Zinn et al (1999), observed no effect on

ruminal pH or VFA molar proportions within the rumen for steers fed diets with

yeast. Other studies have observed using yeast increased the average rumen pH in

dairy cattle (McAllister et al., 2011). Inconsistent results between studies suggests

more research is necessary to observe the strains of yeast, different levels and

their handling procedures are needed to achieve improved results every time yeast

is included in the diet.


8

A concern with increased ruminal pH results from these studies is many

have been derived from dairy cattle (Desnoyers et al., 2009, Thrune et al., 2009).

This could influence the outcomes of many studies because dairy cattle have

greater DMI than beef cattle. In a meta-analysis by Desnoyers et al. (2009)

observed ruminal pH levels by 0.03 when yeast was included in the diet.

Concentrations of VFA within the rumen increased in the diet on average of 2.17

mM when yeast was included in the diet (Desnoyers et al., 2009).

The average ruminal pH values were greater in yeast-supplemented cattle

with a pH of 6.53 vs. the control at 6.32, as well as maximum pH values of 7.01

vs 6.80, and minimum pH values of 5.97 vs 5.69 (Thrune et al., 2009). The

increase in ruminal pH helps to combat acidosis because the animals spend less

time in the sub-acute acidosis zone between 5.60 and 5.00, which provides a more

stable ruminal environment for the ruminal microbiota. However, a concern is the

amount of time the rumen spends in the sub-acute acidosis level at a pH between

5.00 and 5.60 (Gonzalez et al., 2012). Thrune et al. (2009) and Vyas et al (2014),

observed the rumen environment spent less time below a pH 5.60 when diets were

supplemented with yeast. Thrune et al. (2009), observed reduced VFA

concentrations in the rumen when feeding yeast, which may attribute some to the

improved rumen pH, however, this was not the same case in all studies (Newbold

et al., 1996). Vyas et al. (2014) observed both active and killed dry yeast in the

diet improved mean and minimum rumen pH, suggesting even when stored under

non-ideal conditions, yeast could still improve the ruminal fermentation

environment. While these results appear to be positive, the effect of yeast in the


9

diet of growing beef steers needs to be researched further to ensure products

provide similar responses noted in dairy cattle under a variety of conditions,

whether it is in the finishing diet of feedlot cattle or used during the

backgrounding period when high roughage diets are utilized. By studying the

results from various studies, it has been hypothesized yeast may work in various

pathways throughout the digestive tract (McAllister et al., 2011).

Lactic Acid Utilization

Yeast works through various pathways in the rumen to improve nutrient

digestibility. Yeasts stimulate the growth of lactic acid utilizing bacteria, which

metabolize lactic acid within the rumen (McAllister et al., 2011, Robinson and

Erasmus, 2009, Miller-Webster et al., 2002). This results in reduced acidosis risk

and the subsequent sloughing of rumen walls, additionally reducing the risk for

liver abscesses, leading to a more stable ruminal environment (Moya et al., 2009,

Ghorbani et al., 2002). Many growth performance improvements observed when

beef cattle were fed yeast were due to stimulation of cellulolytic and lactate

utilizing bacteria in the rumen (Martin and Nisbet, 1992). When fed high

concentrate diets, a reduction in pH is inevitable as the starch is utilized quickly in

the rumen environment by microbial cells to produce VFA and lactic acid. A

reduction in pH could leave the rumen in a state of acidosis, reducing intake

consistency, creating an undesirable rumen environment (Desnoyers et al., 2009).

Wohlt et al. (1991) speculated yeast also stimulated growth factors of cellulolytic

and proteolytic bacteria in the rumen, specifically in cattle fed high concentrate

diets (> 50%), which was also observed by Wiedmeier et al. (1986) improving the


10

digestibility of crude protein and fiber. Increasing cellulolytic and proteolytic

bacteria boost the energy derived from the fiber from the diet (Beauchemin et al.,

2003).

Fiber Digestibility

Including yeast in the diet of cattle fed high cereal grain diets, increased

DMI and nutrient digestibility, specifically fiber when researchers observed an

increase of 27% in cellulolytic bacteria (Weidmeier et al., 1986). In a review by

McAllister et al. (2011), fiber digestion was improved when yeast was included in

high concentrate diets of feedlot cattle. Despite the fact including yeast in the diet

improves fiber digestibility, a meta-analysis found the acetate to propionate ratio

in the rumen not influenced (Desnoyers et al., 2009). When fiber is digested, it

results in the production of acetate, and propionate is produced from the

breakdown of starch (Goad et al., 1998). In this meta-analysis, the authors also

observed as the concentrate in the diet increased, the effect of yeast on the

concentration of lactic acid in the rumen decreased by 0.9 mM (Desnoyers et al.,

2009), which would is beneficial in the feedlot industry as the level of concentrate

in the diet increases. The improvement in rumen pH creates a more stable ruminal

environment, improving the environment for cellulolytic bacterial growth.

Ideally, yeast products are used to improve the growth performance of

cattle and prevent nutritional health disorders. Saccharomyces cerevisiae is a

yeast product and requires an aerobic environment to function, and it quickly

removes oxygen from the rumen (Newbold et al., 1996). The removal of oxygen

creates an anaerobic environment in which the anaerobic bacteria found have a


11

more suitable and stable environment for increase DM digestion when using two

yeast products, which was 71.6% and 69% versus 66.6% (Miller-Webster et al.,

2002). However, S. cerevisiae is an aerobic organism, and the length of time it

works within the anaerobic environment of the rumen is unknown (McAllister et

al., 2011). According to Chaucheryas-Durand et al. (2008), 16 L of oxygen can

enter the rumen throughout the day, affecting the anaerobic microorganisms, and

some yeast strains can consume the oxygen, resulting in a more desirable

environment for anaerobic microbial bacteria, improving nutrient digestibility,

and energy derived from the diet (Newbold et al., 1996).

Ammonia Uptake

A final theory on the benefits of yeast and its mode of action is it improves

ammonia uptake from the rumen, thus improving microbial protein production

through better protein recycling (Miller-Webster et al., 2002). Stimulation of

proteolytic bacteria resulted in less variation in ammonia in the rumen, suggesting

a more stable rumen environment (Harrison et al., 1988). This improved stability

implies rumen microbes have better uptake of ammonia to use when multiplying,

providing more undegradable intake protein for cattle. Beauchemin et al. (2003)

observed an increase in microbial protein flowing from the rumen into the lower

gastrointestinal tract, which might result in an increased requirement for

degradable intake protein (DIP) in growing cattle. However, of all mechanisms of

action, this has been the least documented effect of yeast inclusion in the diet

(Miller-Webster et al., 2002). By utilizing more dietary energy, the animal

improves growth performance.


12

Supplementation

When including yeast in the diet of growing cattle, it is important to

consider the many different aspects of yeast that affect its viability. The FDA does

not regulate yeast, so researchers and producers need to be cognizant of the

conditions under which the yeast was handled. Yeast is generally sold as an active

and living organism, and it could be inert if stored improperly. Storing yeast

under conditions that allow it to remain inactive until it comes into contact with

the rumen is most ideal. The different varieties of yeast available affect how the

yeast acts within the ruminal environment. The following sections further

evaluate how yeast should be fed and the direct effect of handling on the

production of the animals involved. Similar to other feed additives; precise levels

and conditions are necessary to reap the best benefits for the cattle and their

performance. Yeast is a unique product that can impact many areas of the beef

production cycle, so its impact during various phases of the animal’s life needs to

be evaluated further.

Levels

The amount of yeast included in the diet can be dependent on strain,

production, colony forming units of the yeast, and intake of each animal.

Researchers observed when cattle were placed in stressful conditions adding yeast

to the diet increased DMI (Yoon and Stern, 1995). However, the inclusion of a

dried yeast culture grown in a corn medium from 1 to 2 % of the diet did not

increase DMI further from 6.2 kg/day to 6.4 kg/day, compared to the control diet


13

of 5.6 kg/day, suggesting optimal levels to be included in the diet on a DM basis

is 1 % (Yoon and Stern, 1995). The ability of yeast to effect growth performance

depends upon biotic factors such as the yeast strain and its viability as well as

abiotic factors such as storage conditions, animal management and the diet

(Chaucheyras-Durand et al., 2008). Scientists have been selecting yeast strains

based upon their ability to effect ruminal microorganism populations

(Chaucheyras-Durand et al., 2008). Many research trials have used yeast in the

diet at levels of 1% inclusion on a DM basis. Depending on the comparative

intake of the animals being addressed, keeping the yeast levels at beneficial

concentrations would be best for improved production.

Activity

The variety of yeast products available, their viability (killed versus

active), environmental conditions they are stored could affect their capability to

improve growth performance. According to Sullivan and Bradford (2011), an

issue with using ADY is the lack of quality control in regards to these products by

the FDA. A potential reason for some of the issues with inconsistent results from

using yeast is due to the lack of quality control within the products. Sullivan and

Bradford (2011) found exposing ADY to temperatures above 40°C for a period of

two weeks dramatically reduced their activity. When exposed to higher

temperatures, ADY colony forming units were activated, and due to a lack of

available nutrients, they became inert, by as much as 90% over a period of 3

months above 40ºC (Sullivan and Bradford, 2011). The issue with including yeast

products within a vitamin and trace mineral complex is some minerals can oxidize


14

and lyophilize the yeast making the yeast cells inactive (Sullivan and Bradford,

2011). However, it is hypothesized including strong antioxidants within the

vitamin trace mineral premix along with the yeast product; the antioxidants could

protect yeast viability (Sullivan and Bradford, 2011, Walker et al., 2006).

The average time heifers had a rumen pH below 5.80 and 5.60 was

reduced when either a killed dried yeast (KDY) or ADY was supplemented in the

diet of ruminally cannulated beef heifers (Vyas et al., 2014). Yeast can reduce the

risk of sub-acute and acute acidosis in cattle diets, irrespective of whether it is

active or dry. This suggests yeast viability may not be as negatively affected due

to adverse environmental conditions as first hypothesized (Vyas et al., 2014).

Vyas et al. (2014), found supplementing either ADY or KDY in the diet does

affect overall nutrient digestibility, but it may depend on yeast strain. That being

said, the effect of KDY on other aspects of growth performance and the rumen

environment were not studied, and before accepting KDY as an acceptable

product.

Diet Digestibility

There has been an assortment of experiments discussing the efficacy of

yeast to improve digestibility of crude protein (75.4 % vs. 73.8%) and cellulose

(66.3% vs. 61.0%) (Wohlt et al, 1991). As noted previously, yeast improves fiber

digestibility by providing an environment for cellulolytic bacteria to grow and

reproduce. There have been some studies, however, that have also recorded

improved protein, starch, DM and OM digestibility when yeast was included in

the diet as well. Callaway and Martin (1997) observed improved growth of


15

ruminal bacteria in a laboratory setting when exposed to yeast filtrates. As a

result, it has been hypothesized yeast provided nutrients required by ruminal

microbes such as B vitamins, amino acids and organic acids (Callaway and

Martin, 1997). With improvements in growth factors for ruminal microbes when

fed high concentrate diets, yeast may provide nutrients for those microbes. In a

meta-analysis by Desnoyers et al. (2009), OM digestibility was increased via the

supplementation of yeast products in the diet of ruminants. Supplementing yeast

in the diet whether it was ADY or KDY improved the overall apparent total-tract

digestibility of starch without affecting the digestibility of other nutrients (Vyas et

al., 2014). Increasing starch digestibility may be another reason for increased

rumen pH when beef cattle are fed yeast products. Yeast can utilize starch in its

reproductive process, reducing the starch available in the rumen for microbes

(Vyas et al., 2014). Improved starch digestibility is not a response that was easily

replicated in other studies when yeast was used as an additive in the diet.

However, if it can be replicated, that would be extremely beneficial for the beef

industry because it would result in less grain needed to feed the animal, improving

sustainability of the beef industry.

Health

Increasing concern about antibiotic resistance and more stringent

regulations concerning antibiotic use, the adoption of yeast in finishing diets of

beef cattle to improve growth performance appears to be beneficial. Feeding yeast

products in the diet rather than sub-therapeutic antibiotics could potentially reduce

the transfer of resistant bacteria into the human food chain (Chaucheyras-Durand


16

et al., 2008). How cattle respond to yeast also depends upon their physiological

status, it appears yeast in the diet is more effective when fed to stressed animals

(Chaucheyras-Durand et al., 2008). Using yeast culture in receiving diets

improved the cattle response to antibiotic therapy and reduced the days needed to

recover from an Infectious Bovine Rhinotracheitis Virus (IBRV) infection (Cole

et al., 1992). In a study researching yeast influence on morbidity and total sick

days in recently weaned growing cattle, it reduced morbidity overall, as well as

reduced the total number of sick days (Zinn et al., 1999). However, at the end of

the growing phase, yeast supplementation did not impact growth or digestive tract

function (Zinn et al., 1999). While growth performance is not always replicated in

yeast supplementation trials, if health were improved in stressed calves, it could

reduce reliance on antibiotics. While many producers believe most of the stress

cattle are under is during the receiving phase to the feedlot, some stress may occur

during the finishing phase when cattle are growing very large and are living in

poor weather conditions. Yeast appears to be very beneficial in keeping DMI

consistent during the finishing phase because it helps reduce the negative effects

the cattle feel from stressful situations, such as the adaptation period to high

starch diets.

Risk of bloat is a concern when cattle are introduced to the feedlot and

adapted rapidly to high concentrate diets. Bloat is caused by the production of

mucopolysaccharides, which increases the viscosity of rumen fluid and increases

the risk to develop frothy bloat, causing a decrease in animal performance and

potentially death (Moya et al., 2009). Adding yeast to the diet under induced


17

acidotic conditions reduced the overall viscosity of the rumen fluid reducing

frothy bloat risk (Moya et al., 2009). Considering young, high-risk cattle in the

feedlot have a higher risk for bloat as they adapt to high concentrate diets, the

addition of yeast may improve performance of the feedlot and cattle as they grow

through the finishing phase.

Growth Performance

Cattle need to have a consistent DMI, especially during the initiation to

the feedlot, when stress levels are high, causing a risk for compromised health

(Keyser et al., 2007). It was observed feeding yeast to newly received heifers in

the feedlot resulted in heifers returning to a normal DMI more quickly after

needle injections (Keyser et al., 2007). Many researchers argue the capability of

yeast products to improve DMI in growing steers, as many have had conflicting

results as to how much influence yeast has on growth performance (Zinn et al.,

1999). Contrary to the results observed by Zinn et al. (1999), researchers Phillips

and VonTungeln, (1985), were able to report improved ADG by 0.10 kg/day of

growing feedlot steers when fed high concentrate diets (53% corn) were

supplemented with yeast. Yoon and Stern (1995) reported live weight gain

increased by as much as 19% in Friesian male calves when fed a barley/soy diet

that included yeast. However, different results could be obtained in terms of

growth performance based on differing diets from each region and production

system. According to Moloney and Drennan, (1994), the inclusion of yeast in the

diet of growing cattle improved cattle growth performance of animals fed a grass

silage diet with barley-based concentrates. In a study by Moloney and Drennan


18

(1994) they observed improved growth performance of cattle fed high concentrate

diets with yeast inclusion rather than high roughage diets. Recently weaned feeder

steers, which were fed yeast in the diet, had fewer sick days and greater DMI’s

than those calves whose diet did not include yeast (Cole et al., 1992). When

supplementing steers with yeast, Swyers et al. (2014), recorded reduced ADG by

0.14 kg/day compared to cattle not fed any yeast in the diet. Feeding cattle diets

with yeast products improved overall DMI during periods of stress (Cole et al.,

1992). When fed in combination with Selenium and Chromium supplements in

grower lamb diets, yeast improved DMI and increased ADG in lambs by 250 g

per day (Hernandez-Garcia et al., 2015). Overall, it appears yeast supplementation

has a greater effect on ruminal fermentation variables, but this effect does not

directly translate into improved growth performance throughout the growing

phase of beef cattle, because nutrient digestibility appears to be improved, while

improvements in growth performance are not noted as often.

Carcass Characteristics

Yeast supplementation in the diet may improve carcass characteristics.

Supplementing the diet with a yeast product resulted in more carcasses being

graded USDA Choice, in a study comparing yeast supplementation to monensin

(Swyers et al., 2014). When steers were supplemented with a S. cerevisiae as an

alternative to monensin, they had a similar final BW but lower ADG (Swyers et

al., 2014). As mentioned before, improvement in carcass characteristics are

generally not noted because cattle in natural programs are generally fed for longer


19

periods of time, resulting in more time for fat deposition within the muscles,

which improves carcass characteristics such as marbling.

The addition of yeast in the diet did not affect carcass characteristics such

as HCW, carcass quality, or yield grade (Hinman et al., 1998). Similar results

were observed in lambs fed yeast products during the finishing phase (Hernandez-

Garcia et al., 2015). However, carcass response may have been partially attributed

to the age of the lambs at slaughter, as the lambs did not have enough time to

physiologically respond to the yeast (Hernandez-Garcia et al., 2015). Contrary to

these results, Mir and Mir, (1994), found adding a live-yeast culture to the diet in

growing finishing feedlot steers it improved final weights and carcass weights of

steers when fed rolled barley based diets over control diets. When yeast cultures

were mixed with a lasolacid additive (an ionophore) to the diet however, no

additive effects were seen within the steers in either growth or carcass

characteristics, unlike would be expected because it has been hypothesized they

work with different modes of actions (Mir and Mir, 1994). Ionophores work

through affecting the ion balance of gram-positive bacteria, while yeast works

through improving the growth of bacteria that utilize lactate, causing an improved

environment for cellulolytic bacteria. If an additive effect had been observed, this

would be positive news for beef producers who own natural program cattle trying

to emulate conventional practices in terms of growth performance.

Cost

Cattle fed yeast alone are less efficient than those animals fed a monensin

based diet, and it costs 5.82% more to feed them than conventionally raised cattle


20

if diet costs are equal (Swyers et al., 2014). That being said, some consumers are

more willing to pay a premium for these naturally raised animals. Nonetheless,

before entering into a natural program, ensuring a market for these animals is

imperative, or the producer will be forced to take conventional prices while

raising cattle at a lower efficiency and higher cost (Swyers et al., 2014).

Dependent on cost of ingredients and cattle, yeast could be beneficial to feedlots

that are not only focus on natural production, but those feedlots looking to reduce

stress in cattle in all phases of production. According to Swyers et al. (2014),

natural producers need a premium of 6% to realize a profit if yeast products were

included in a high concentrate diet that included 63.5% steam-flaked corn.

Implications

Like many products used within the beef industry, producers have to be

cognizant of feeding at high levels, and discover adequate levels of inclusion

within the diet to enhance growth and production of the animal without impeding

health (Yoon and Stern, 1995). Yeast inclusion in the diet decreased morbidity of

steers during the receiving phase at the feedlot; however, many studies did not

research the effects of yeast in the diet during the finishing phase of the feedlot,

which may have an impact during a longer feeding trial (Keyser et al., 2007).

Conclusions

Although further research is required to study dose and strain of yeast to

be used in beef cattle diets to improve growth performance, there appears to be an

advantage in using yeast. Unfortunately, the results observed thus far in research

in terms of improvement of growth performance and carcass characteristics have


21

been inconsistent and need more validation to be adopted wholly in the beef

industry. However, improvements that have been noted may be valuable to those

producers who are marketing their animals to niche markets and are looking to

improve their performance. In conclusion, with the natural beef production niche

growing and with the increasing vocalization of the consumer community, it is

imperative to treat the results of the studies using DFMs and probiotics in feedlot

diets very seriously as we look to alternatives to sub therapeutic use in

concentrated animal feeding operations, specifically within the beef industry.

Considering the cost of beef production, the beef industry needs to be proactive to

consumer concerns because their product costs much more than other protein

sources. Producers need to be able to sell it as a safe and affordable product to be

enjoyed by all consumers. The major effect of yeast is it improves the ruminal

fermentation environment when cattle are consuming differing diets and under

stressful conditions. Similar to ionophores, yeast modifies the rumen

environment, helping to make it more stable for the rumen microbes, thus

improving the digestibility of the diet and the health of the animal.

The objective of this research trial was to evaluate the effect of yeast in

natural program steers on steer growth performance, total tract apparent nutrient

digestibility, feeding behavior and carcass characteristics. The authors were

anticipating an improvement in growth performance and apparent total tract

nutrient digestibility with increasing levels of yeast in the diet. Yeast was

included in the diet to be targeting on average 0, 25 or 50 grams per head per day.

Increasing levels was thought to further improve and stabilize the ruminal


22

environment, thus translating to improved growth performance throughout the

finishing phase and total tract apparent digestibility. With improved growth

performance, it was also thought some carcass characteristics such as rib-eye area

would be improved. Improving natural program steer growing programs was the

intent because they cannot use conventional methods that improve performance.

Natural producers are looking for a natural alternative to improve cattle growth

without using implants, antibiotics or beta agonists. This study observed the effect

of yeast in steers fed steam-flaked corn-based finishing diets, and focused on the

finishing phase of steers in the feedlot. The following chapter discusses the effect

of yeast used in natural program steers fed a steam-flaked corn-based finishing

diet.


23

ADAPTATION OF BEEF FINISHING STEERS TO HIGH

CONCENTRATE FINISHING DIETS

Introduction

Improving the growth performance of cattle in the feedlot is important to

develop efficiency and reduce the cost of gain. As beef cattle adapt to a high

concentrate finishing diet from a high roughage based diet, it has to occur over

time to acclimate the rumen environment. During this transition period, bulky

high fiber ingredients are required to provide the roughage needed to initiate

rumination and provide gut fill. An issue with the adaptation period in the feedlot

is it uses high levels of roughages accounting for 50% of the total roughage costs

of the feedlot period. (Mader et al., 1993) These roughage sources, such as alfalfa

hay, are expensive per unit of energy because of their low energy density. Due to

their high logistical costs, finding new and low cost ingredients to utilize during

the adaptation period would be beneficial. A benefit of cattle is they can utilize

low quality forages to produce high quality protein. There are a lot of low quality

roughages available in most regions available. The concern is not all roughages

have been studied in the feedlot setting, so their ability to replace traditionally

used roughage sources during the adaptation period is not always well understood.

How an animal responds to new roughage sources is not always well researched,


24

and rumen variables and digestibility of the diet during the period, and how it

affects the animal in the finishing phase need to be further elucidated.

Co-products can be utilized in replacement of traditional bulky ingredients

such as alfalfa hay. The advantage of co-products is they are generally high in

fiber and are not usable to industries other than in livestock production. Co-

products are available from a variety of industries, DDGS from ethanol

production and WCGF from wet corn milling, or cotton burrs from cotton

production in the southern plains. These products have generally had the energy

(starch) removed for the primary industry they are involved in, leaving a

concentrated source of fiber and other nutrients for cattle to consume. These are

generally bought at a lower price and fulfill the need for roughage source in

adaptation strategies, reducing demand for alfalfa hay. These roughage sources

help the rumen environment adapt to high starch diets. This could provide

physically effective fiber, which stimulates rumination, resulting in more saliva,

buffering the rumen, and reducing sub acute and acute acidosis risk. Depending

on the nutrient composition of the byproduct utilized, each can have varying

benefits on beef cattle performance, which is the reason for researching adaptation

strategies.

Cotton burrs, more commonly known as gin trash in the southern regions

of the United States, are widely available as a byproduct of the cotton processing

industry, made up of the immature bolls, stems and leaves. Cotton is commonly

grown in the southern United States, resulting in cotton burrs being widely


25

available and might provide an economic benefit for feedlots if its use can be

justified during the adaptation period to high concentrate diets in the feedlot.

Although inexpensive, effect on steer acceptance and consecutive effect on

growth performance is necessary before using it as a roughage source in the

adaptation process in the feedlot. If cotton burrs can be used in place of alfalfa

hay in the adaptation period of the feedlot, feedlots could potentially reduce

overall cost of feeding the cattle and improve their profit margins, all the while

not compromising the health of the cattle.

Adaptation Period

The primary goal of the adaptation period is to familiarize rumen

microbiota to high levels of starch without harming the growth performance of the

animal or the ruminal environment. Adapting the rumen requires a shift from

cellulolytic bacteria, which typically degrade cell wall, to amylolytic bacteria,

which more effectively digest starch (Bevans et al., 2005). Doi and Kosugi,

(2004) predicted 80% of the energy needs and 50% of the protein needs of a

ruminant come from the ruminant microbiota, resulting in a need to keep the

microbial population stable throughout the feedlot phase in order to maintain

growth performance. When cattle diets are abruptly switched from high roughage

to high concentrate, the resulting decrease in pH is largely due to the increased

production of lactic acid (Owens et al., 1998). This drop in pH causes the demise

of microorganisms, harming the rumen and causing liver abscesses and a resultant

reduction in growth performance or even death (Owens et al., 1998). When


26

evaluating new roughage as a viable source in adaptation diets, the rumen

environment, health, growth performance and carcass characteristics all need to

be evaluated. Unfortunately, rumen response has not been well documented for

different adaptation strategies (Leedle et al., 1995). Studies that evaluate

metabolic response do so in week long periods, which do not challenge cattle as

much as diets which are stepped up over a period of days rather than weeks.

Research evaluating shorter periods of time for adaptation generally evaluates

beef cattle growth performance rather than metabolic response which can be

observed in ruminally-cannulated steers. A lot of the variation in length and

concentration of roughage in the diet depends on the management of the cattle,

their geographic location, their background, the environment and the nutrient

requirements of the cattle.

Restricting the intake of cattle during the adaptation is a tool to help

reduce inconsistencies in intake and helps cattle more effectively adapt to high

concentrate diets (Choat et al., 2002). Reducing fluctuations in intake during the

adaptation period could help cattle respond to the drop in pH more effectively as

well as reduce digestive upsets due to increased high concentrate loads. Leedle et

al. (1995) reported cattle were stressed when fed diets which continually differed

in nutrient concentration and caloric values at intakes greater than 2% of their

current body weight. Choat et al. (2002), Bierman and Pritchard (1996), and

Weichenthal et al. (1999) observed that restricting dietary intake during the

adaptation period of the feedlot phase reduced total DMI during the period and


27

improved feed efficiency. The issue with restricting feed intake during the

adaptation period is it may reduce growth performance of the cattle, placing them

at a disadvantage during the finishing phase (Choat et al., 2002). Finding balance

between those restricted intakes without decreasing growth performance is

difficult to achieve. Another option of adapting cattle to a high concentrate diet is

the use of bunk management to control the intake of growing cattle. When cattle

have ad libitum access to feed, generally a reduction in intake occurs after a

period of time, due to overconsumption of grain, leading to a reduction in ruminal

pH, leading to acidosis and health issues, reducing intake (Tremere et al., 1968,

Brown et al., 2006).

Methods

There are many methods to adapt cattle to high concentrate diets

efficiently and safely. The issue with adapting cattle to high concentrate diets,

which has been mentioned earlier, is the fact it can cause digestive upsets such as

acidosis and bloat if it done too quickly (Kunkle et al., 1976). The most common

method of adapting cattle to high concentrate diets going from a diet of 55%

concentrate to 90% concentrate over a period of 14 days or less (Brown et al.,

2006). This increase in concentrate can cause reduced performance due to dietary

upsets from the high-energy diet and influx of lactic acid (Brown et al., 2006). In

a study by Brown et al. (2006), it was observed limiting the intake in the diets

versus ad libitum of steers during the first 28 days of the feeding period, the

animals consumed less and gained more efficiently than animals fed higher


28

energy levels during the same period. This continued to the end of the feeding

period, where cattle that were initially limited had a 4% improved feed efficiency,

despite having clumped papillae in their rumens at slaughter (Brown et al., 2006).

Other studies studying a 7 day adaptation period with increasing concentrate in

the diet from 55 to 95% found reduced ADG by 10%, and reduced G:F by 9%,

compared to those over 14 days (Brown et al., 2006).

Ingredients, Time, and Sorting

There are many tools available to feedlots to adapt cattle to finishing diets.

While diets can vary from feedlot to feedlot the same basic structure of each diet

remains intact, which is decreasing roughage balanced by increasing concentrate.

Along with common ingredients, producers can also utilize growth-promoting

technologies to allow animals to grow more quickly and efficiently. These

technologies include steroidal implants to increase lean accretion and ionophores

are commonly used to help stabilize the rumen environment to improve

efficiency. In a study by Galyean et al. (1992), researchers observed the effect of

including laidlomycin propionate and monensin plus tylosin on the growth

performance of feedlot steers during the adaptation phase. Laidlomycin

propionate yielded improved rates of gain of 2.6% over control steers, and 4.2%

over the monensin/tylosin treated steers. Monensin is the ionophore of choice

because it reduces DMI during the finishing phase, improving G:F ratios.

Laidlomycin is not known for these properties; however, Galyean et al. (1992)


29

observed feeding laidlomycin propionate was just as effective to feed during the

adaptation phase as monensin.

When cattle enter the feedlot, they can potentially be stressed due to

travel, recent weaning, and mixing of cattle from different backgrounds. This

stress causes a reduction in feed intake, further depressing the activity of their

immune system. This stress can cause as much as a 75% reduction in rumen

fermentative activity, and can stay decreased for as long as five days later (Loerch

and Fluharty, 1999). Decreased DMI due to stress coupled with an increase in

concentrate in the diet could increase the risk for acidosis and bloat, as the rumen

environment cannot handle the changes it is placed under. During the stressful

periods, cattle require higher nutrient densities to meet their needs while they

have decreased DMI by as much as 38% (Loerch and Fluharty, 1999). Increasing

the energy density of the diet may harm the ruminal microorganisms because of

the readily available starch in the diet (Loerch and Fluharty, 1999). The

adaptation of cattle to new diets involves the introduction of new diets every few

days; causing a reduction in DMI, shocking ruminal microorganisms with rapid

pH drops. In more recent research, it has been observed cattle fed diets with

industry recognized RAMP (Cargill), can be adapted to diets more quickly than

usually while improving ADG by 0.09 kg/day throughout the finishing phase and

HCW by 8.00 kg (Anderson et al., 2015). This can be explained by the fact

RAMP is composed of highly digestible fiber which provides a rumination source


30

while decreasing reliance on high fiber, low energy dense sources which are not

as digestible (Anderson et al., 2015).

In a study by Mader et al. (1993), the authors observed a tendency

increased liver abscess scores (1.34 vs 0.91) for animals adapted to a high

concentrate diet with alfalfa hay over alfalfa silage. They hypothesized this result

is seen because more sorting occurs with dry feeds over wet feeds. Feeding a

silage rather than hay as a roughage source in adaptation diets improves gains and

intakes, which may be harmful when studying cotton burrs as part of the

adaptation diet because they are extremely dry and large which could result in

more sorting and reduction in growth performance. Perhaps more grinding to

make a more consistent product to mix in with the rest of the diet would help to

decrease sorting, but that adds extra costs to the maintenance and labor needed to

take care of the roughage source.

Health

Acidosis

Acidosis is a metabolic disorder occurring when there is a digestive upset

within the rumen due to a sudden high starch load (Gonzalez et al., 2012).

According to Galyean and Rivera (2003), although mortality rates are low within

the feedlot at less than 1%, a staggering 30-42% of those deaths are due to

digestive disorders. There are two types of acidosis, sub-acute and acute. Acute

acidosis occurs when the ruminal fluid is at a pH of 5.0 or lower and sub-acute


31

appears when rumen pH is between 5.00 and 5.60 (Owens et al, 1998 and

Nagaraja and Titgemeyer, 2007). Sub-acute acidosis rarely shows clinical

symptoms, but it potentially decreases growth performance of the animal, while

acute acidosis causes clinical symptoms and sometimes death (Owens et al.,

1998) being very costly to the beef industry. Acidosis is a risk during the period

of adapting cattle because cattle are being rapidly switched from a high roughage

diet to a high concentrate diet could shock rumen microorganisms as they digest

large amounts of starch, increasing the lactic acid load dropping the rumen pH

resulting in acidosis, because microbes do not further utilize lactic acid (Nagaraja

and Tigemeyer, 2007). The acidotic rumen may adversely affect intake, causing

inconsistent intake from day to day, further increasing the risk for acidosis as the

animal gorges on feed at random events, eats quickly and reduces rumination

production (Gonzalez et al., 2012). Increased chewing activity causes more saliva

to be produced, which buffers the acid load in the rumen (Beauchemin et al.,

1994). Adaptation is necessary in the rumen to assist microbiota to stop them

overloading the microbiota with organic acids (Gonzalez et al., 2012).

Bloat

Another side effect of rapidly changing the rumen environment in cattle is

it increases the risk for bloat (Cheng et al., 1998). Bloat, similar to acidosis,

decreases animal growth performance and poses a serious risk for fatality (Cheng

et al., 1998). Bloat is often a result of acidosis because as the rumen pH drops and

the environment becomes unstable for the ruminal microbial population to grow,


32

the rumen fluid contents become less motile, causing foam to build up, resulting

in frothy bloat (Cheng et al., 1998). The froth builds up quickly, causing bloat

which is difficult to be identified and treated in time to save the life of the animal.

Foamy bloat causes death quickly in animals because the gas build-up within the

rumen places pressure on the lungs causing death within minutes (Cheng et al.,

1998, Vasconcelos et al., 2008). There are two different types of bloat, free gas

and frothy, where frothy bloat is more common in feedlot cattle (Vasconcelos et

al., 2008). According to Vasconcelos et al. (2008), the cause of frothy bloat can

be a result from insufficient roughage in the diet, which reduces rumination and

eructation. Elam and Davis (1962) observed adding mineral oil to the diet also

reduced the incidence of frothy bloat. When decreasing roughage content, the risk

for bloats increases. Additionally ionophores are used to control bloat

(Vasconcelos et al., 2008) because they change the rumen environment. The

adaptation period is extremely important in the feedlot and getting cattle to the

finishing phase without bloating is extremely beneficial. The extent to which

grain is processed effects antinutritional disorders, and if corn is steam-flaked to

lighter densities, it could predispose cattle to bloat and acidosis (Vasconcelos et

al., 2008). Ramsey et al. (2002) observed cattle fed diets with more rapidly

degradable starch had a greater risk for bloat and acidosis. There is extreme risk

for cattle to bloat with the quickly changing diet and high levels of stress cattle

are under during the first few weeks of the feedlot. Proper adaptation is necessary,

if done too quickly, cattle are at risk for bloat, but too slowly, cattle have reduced

performance and more days in the feedlot.


33

Growth Performance and Feed Intake

The time during which cattle are adapted to finishing diets impacts their

performance during the finishing phase. Research of the adaptation phase has

been occurring for many years, and many different strategies have been

investigated. Kunkle et al. (1976) studied methods for adapting cattle and

observed cattle can be adapted to high concentrate diets in periods as short as ten

days, as long as the cattle were properly managed. Researchers observed cattle

adapted to high concentrate diets with corn silage performed better during the

finishing phase than cattle which were adapted to high concentrate diets without

the use of corn silage (Kunkle et al., 1976). The corn silage may set up the rumen

for a high starch load and reduced rumen pH due to the lactic acid within the corn

silage. Lactic acid prepares rumen microbes for increased acid, and when the high

starch load is consumed, the microbes will not be shocked and will efficiently

digest the ingredients. However, while corn silage prepared cattle more quickly

for a finishing diet, those cattle fed hay diets in the adaptation phase had greater

gains (Kunkle et al., 1976). This validates the idea many adaptation strategies can

be utilized by the feedlot to adapt cattle to full finishing diets. The strategy the

feedlot uses is more dependent on the cost of ingredients, management,

environment and geographic location of the feedlot.


34

Sub acute acidosis causes a depression in feed intake, as mentioned

previously (Gonzalez et al., 2012, Bevans et al., 2005). This decrease in feed

intake and resulting decline in steer performance shows adequate adaptation is

necessary in order to successfully run a profitable feedlot. Bevans et al. (2005),

researched whether or not quick adaptation periods could replace slow adaptation

periods to a high concentrate diet were effective. It was found even lengthy

adaptation strategies still causes some acidosis, which may be a result of

environment, genetics, physiology or even background of the animal (Bevans et

al., 2005). When the adaptation period is lengthened, the producer runs the risk

for losing performance by not meeting the gain potentials of the animal. This

results in needing to find a balance between compromising the health of the

animals while getting the highest rate of performance out of them.

Ruminal Bacterial Community

The bacterial community within the rumen is not well understood because

of the lack of knowledge of the millions of bacteria, protozoa and fungi present

(Fernando et al., 2010). Only a few bacterial species are known at this time until

the methods for extracting and analyzing the microbes from the rumen become

more effective to study the smaller groups of microbes within the rumen.

However, even though most bacterial species are unknown, the knowledge of the

species that have been studied is improving and diets are being tailored to

encourage bacterial growth. With improvement of genetic quantitative and

qualitative technologies, more bacterial species will be analyzed in the future, and


35

knowledge of the rumen will only increase, improving understanding of the beef

animal will allow for better production methods within the beef industry.

When evaluating the response of the rumen to changing diets, specifically

during the adaptation phase, it is imperative to evaluate the bacterial community

(Fernando et al., 2010). Researchers are aware a dramatic decrease in pH

negatively effects the rumen environment and negatively affects the bacterial

populations, thus potentially decreasing animal growth performance for the

remainder of the feeding period. Fernando et al. (2010), found two distinctly

different bacterial species in the rumen when the diet was of high roughage as

compared to a high concentrate diet. When fed a high roughage diet, the bacteria

Fibrobacteres, was most commonly found, as compared to a high concentrate diet

where the most common bacterial species found was Bacteroidetes (Fernando et

al., 2010). During this same study, Megasphaera elsdenii, Streptococcus bovis,

Selenomonas ruminantium and Prevotell bryantii increased considerably during

the adaptation phase, while the Fibrobacteres bacteria decreased (Fernando et al.,

2010). The more researchers can learn about the environment of the rumen, the

more opportunity they have to modify diets to meet the microbial needs of the

animal, improving the efficiency with which producers adapt cattle. Fernando et

al. (2010) found increasing the starch utilizing bacteria populations did not occur

until a diet contained a higher ratio of concentrate to roughage, despite the fact the

two previous diets were increasing the level of concentrate in the diet from zero.

When cattle are adapted to high concentrate diets, there is an increase in


36

amylolytic bacteria than in cattle adapted to hay diets over a similar period of time

(Goad et al., 1998).

Cotton Burrs

The adaptation phase is a costly period in the feedlot as cattle consume

high amounts of roughage, which have low energy density and high logistical

costs. Before new roughage sources can be utilized in the diet of growing cattle,

they must first be evaluated to determine their relative roughage value in relation

to other known adaptation strategies. Cotton burrs are a byproduct of the cotton

ginning process and provide an ingredient for feedlots to use in place of costly

traditional sources while adding value to the byproduct for cotton producers.

Cotton burrs have a high fiber content, which is a requirement for adaptation diets

as cattle acclimatize from high roughage to high concentrate diets (Blasi et al.,

2002). Unfortunately, cotton burrs have not been evaluated as an additive in beef

cattle adaptation diets in the feedlot, so its effectiveness is unknown.

The potential of cotton burrs to be used as a roughage source in place of

costly traditional roughage sources such as alfalfa hay is great, especially in

locations where cotton production is extensive. Cotton burrs are derived from the

cotton production, yielding from the stripping technique, which pulls the cotton

from the plant. More cotton burrs are derived from more drought tolerant varieties

of cotton, which are more common in areas such as Texas (Conner and

Richardson, 1987). When producing cotton bales, a cotton bale that weighs 480


37

pounds can yield as much as 150 to 200 pounds of cotton burrs (Stewart, 2010),

which is a lot of residue. Cotton burrs has a very low bulk density, resulting in

expensive transport costs, resulting in a product that is more available for

southern producers and those close to cotton producing regions than those who

are not (Stewart, 2010, Bernard et al., 2001).

Cotton burrs are not regularly used in feedlot diets due to its low

digestibility (Stewart, 2010). Conner and Richardson (1987) observed poor

digestion of cotton burrs due to the high lignin content of the ingredient, which is

harder for ruminal microorganisms to break down. Cotton burrs also have limited

available protein in the diet (Brown et al., 1979). They have been evaluated in

pregnant cow maintenance diet, and it has been observed cows fed diets with high

levels of cotton burrs with corn grain supplementation were able to maintain body

weight. Whiting et al., (1988), observed feeding Holstein heifers a diet that

included cotton burrs rather than alfalfa hay helped to control energy intake and

reduce overall feed cost. Some research has evaluated the use of products such as

alkali to break down the cotton burrs prior to feeding in order to improve nutrient

digestibility (Conners and Richardson, 1987). It is currently advised to use cotton

burrs as a roughage source as part of a balanced ration, and must undergo testing

because it can be variable in composition (Myer, 2007).

Brown et al. (1979) concluded including cotton burrs at no more than 60%

in the diet in place of alfalfa cattle had similar performances. Brown et al. (1979)

was also concerned about the availability of protein in the cotton burrs diet. While


38

its use has primarily been as a product in pregnant cow diets, it has potential to be

a roughage source during the adaptation phase in the feedlot. Evaluating the use

of cotton burrs in the diet of growing feedlot steers could potentially alleviate

costs for the feedlot while adding value to cotton byproducts, improving the

sustainability of both industries.

Implications

The period of adaptation is necessary to acclimate the rumen of cattle to

high starch content in diets. Fortunately for feedlot operators, the way cattle can

be adapted to these high concentrate diets can be variable, allowing feedlots to be

flexible when adapting cattle based on their management, location, available

feedstuffs and the cattle. The current trend of feedlots is to reduce the amount of

time spent adapting cattle to high concentrate diets because roughly 50% of the

roughage included in the diet is used during the adaptation phase. Roughages

have a low energy density compared to grains, resulting in high costs per energy

unit. Among these methods for reducing costs to the feedlot during the adaptation

phase, two can be highlighted: the first is reducing the time spent by the feedlot

adapting the cattle to a high concentrate diet. The second option is to utilize

byproducts from other industrial processes to reduce cost of the diet. This option

also provides higher energy ingredients without having high starch levels, thus not

negatively affecting the rumen. Cotton burrs may fall under this second category,

as it is a valuable byproduct from the cotton industry. As a high fiber product and

a byproduct, cotton burrs could potentially provide an acceptable alternative to


39

alfalfa hay during the adaptation phase. Cotton burrs may be a good product to

use during the adaptation phase if the cost of the ingredient outweighs the benefit.

The following study evaluated the response of beef cattle to cotton burrs in the

adaptation phase of growing steers.

Cotton burrs are readily available in cotton producing areas of Texas, and

may provide a source of roughage for the adaptation phase at a reduced cost

compared to alfalfa hay. Using byproducts as a roughage source during the

adaptation phase has proven effective in reducing the costs of the feedlot as well

as provided an opportunity for producers to utilize products specific to their

geographic location. The effect of a roughage source on the rumen during the

adaptation phase is necessary to evaluate whether a forage source effectively

combats acidosis from increasing starch loads in the diet during the ever changing

adaptation phase. The "relative forage value" of cotton burrs is unknown and

further research is required to evaluate its' value relative to a known source of

roughage such as alfalfa hay on ruminal fermentation variables.


40

CHAPTER II

EFFECT OF A LIVE YEAST PRODUCT IN A FINISHING FEEDLOT

DIET ON GROWTH PERFORMANCE, DIGESTIBILITY, AND

CARCASS CHARACTERISTICS IN A NATURAL PROGRAM FEEDLOT

Abstract

Effects of live yeast (Saccharomyces cerevisiae) fed to beef cattle

finishing diets on growth performance; apparent digestibility, carcass

characteristics, and feeding behavior were evaluated. Control (CTL), Low Yeast

(LY), and High Yeast (HY) steam-flaked corn-based finishing diets were fed to

steers (n = 144; 341 ± 52 kg) in a completely randomized block design. Animals

were kept in a natural program, in which technologies such as implants,

ionophores, and antibiotics were not utilized. Yeast was mixed with cottonseed

meal as a premix and included in the diet at a 1% DM basis. Data were analyzed

using the GLIMMIX procedures of SAS, and pen (n =12/treatment; 4 steers/pen)

represents the experimental unit. Feed efficiency tended to be improved (P =

0.08) between days 0 to 183 for the LY diet by 4.3% over other treatments. The

number of premium choice carcasses increased linearly (P < 0.01) with increasing

yeast inclusion in the diet at 33.3%, 68.8% and 70%, respectively. There was a

tendency (P = 0.09) for choice carcasses to be increased linearly with increasing

yeast levels in the diet. A quadratic response was shown for apparent digestibility,

in which steers fed LY had improved digestibility (P < 0.01) of dry matter by


41

5.4%, organic matter by 4.8%, NDF by 15.2%, ADF by 20.2%, CP by 6.2%, and

EE by 2.5%. Intake of DM, ADG, and G:F carcass adjusted were not affected by

dietary treatments. Moderate inclusion of live yeast improved efficiency of

nutrient utilization and carcass characteristics of steers fed steam-flaked corn-

based finishing diets, which tended to positively affect gain efficiency on a live

basis.

Key words: behavior, cattle, digestibility, natural, yeast


42

Introduction

Growth promoting technologies are utilized by the beef industry to reduce

health issues and improve growth performance during the growing and finishing

phase of feedlot cattle. However, despite the fact these technologies improve the

efficiency of the beef industry, public scrutiny is forcing the more judicious use of

these products. Because of this, natural options offer a premium to producers,

while potential improvement of gastrointestinal health and animal growth

performance can be expected, when compared to animals not fed such feed

technologies. Without the use of growth promoting technologies, efficiency

within the feedlot is reduced, thus the use of natural products to improve growth

is justified. Unfortunately, there is conflicting evidence about whether or not the

use of yeast in the diet improves growth performance, digestibility, and carcass

characteristics of cattle during the finishing phase fed steam-flaked corn-based

diets.

Yeast products included in the diet stimulate fiber-digesting bacteria and

improve digestibility of the nutrients consumed, which allows the animal to grow

more efficiently (Wiedmeier et al., 1987). Yeasts are used for more than just

growth performance; they are also used to improve health during stressful

situations and carcass quality (Hernandez-Garcia et al., 2015). While the impact

on growth performance has been inconsistent, the varying modes of action of

yeast in the diet and its impact on digestibility of nutrients have been well

documented. When yeast is supplemented in the diet, cellulolytic bacteria within

the rumen are stimulated and fiber digestion is improved (Hernandez-Garcia et


43

al., 2015). The objective of this study was to determine if the supplementation of

yeast within the diet improved growth performance, digestibility of nutrients,

behavioral response to the diet, and carcass characteristics of finishing feedlot

cattle fed steam-flaked corn-based diets.

Materials and Methods

All experimental procedures involving the use of animals were done in

accordance with Texas Tech University Animal Care and Use Committee

Protocol 15044-05. The experiment was conducted at Texas Tech’s University

Burnett Center located in Idalou, TX.

Feedlot Growth Performance

On June 4th, 2015, 171 Black Angus cross steers arrived at Texas Tech

University Burnett Center. Cattle were weighed June 5, 2015, given vaccines for

Bovine Rhinotracheitis Virus, Parainfluenza 3-Respiratory syncytial vius,

mannheimia haemolytica, and pasteurella multocida vaccine at 2 ml/hd; a vaccine

for Mycoplasma bovia at 2 mL/hd; fenbendazole at 20mL/hd; clostridium

chauvoei-septicum-novyl-sordellii-perfringens types C&D bacterin-toxoid at 2

mL/hd; Vitamin E, A +D at 5 mL/hd; and ivermectin pour-on at 35 mL/hd. Steers

were separated into 16 receiving pens, and left for approximately two weeks to

recover from the initial processing and transport. During this period and days that

followed until the study started animals were limit fed (2% BW) with standard

receiving diet that included 18.6% steam-flaked corn, 15.23% cottonseed hulls,

and 63.26% sweet bran. On June 17, 2016, cattle were weighed again to sort into

12 blocks at 3 pens/block into 36 pens of four animals each. Cattle within blocks;


44

were randomly allocated into Burnett Center pens (2.9 m wide × 5.5 m deep; 2.4

m of linear bunk space) on June 30, 2015. After a week of acclimation, animals

that had been previously allocated into respective experimental units were sorted

to reduce variation within block, and the experiment was initiated on July 8, 2015,

when initial BW was taken. At this moment, animals started on adaptation diets,

which already contained yeast treatments. Step-up diet 2 was fed for one week,

and included 28.43% steam-flaked corn, 7.19% cottonseed hulls, 41.13% sweet

bran, 15.17% corn silage, 4.99% sorghum silage, 1.05% limestone, 1.35%

supplement and 0.69% of each respective treatment. The step-up diet 3 was fed

for another 7d included 40.72% steam-flaked corn, 3.70 cottonseed hulls, 31.31%

sweet bran, 15.62% corn silage, 5.13% sorghum silage, 1.08% limestone, 1.39%

supplement, 0.33% urea and 0.72% inclusion of each respective premix. On d15,

the cattle were placed on the finishing diet which was fed for the rest of the study,

and is shown in Table 1.

Cattle were sorted into three treatment groups. Each block combined three

pens, and each treatment was randomly assigned to one of the three pens

(randomized complete block design). The three treatment groups were Control

(CTL), which included no yeast, Low Yeast (LY), which targeted for a yeast

intake of 25 g/hd/daily, and High Yeast (HY), which targeted for a yeast intake of

50 g/hd/daily. The yeast used was live yeast Saccharomyces Cerevisiae provided

by ABVista, United Kingdom. These treatments were administered via premixes

included at 1% in the diet on a DM basis. The diets and their nutritional

composition are shown in Table 1.


45

All premixes were made at the Texas Tech University Burnett Center Feed

Mill in a ribbon type mixer (Marion Mixers Inc.) The premix included cottonseed

meal and yeast at increasing levels according to the treatment plan. Diet and

ingredient samples were taken once a week and tested for DM at 100°C forced-air

oven. Diet samples were also frozen from each week and a composite from each

period (35-d) was made throughout the entire study.

Unshrunk body weights were collected on day 0, 35, 70, 105, 140, 183 and

204 before daily feeding at 0630 on each of these days. Weights were taken using

a large pen scale (Cardinal Scale Manufacturing Co., Webb City, MO; accuracy ±

2.7 kg), except by day 0, 183, and 204, where individual BW were taken (Silencer

Chute, Moly Manufacturing, Lorraine, KS, mounted on Avery Weigh-Tronix load

cells, Fairmount, MN; readability ± 0.45 kg; before each use, the scale was

validated with 454 kg of certified weights). Collecting the orts and deducting it

from the total dietary DM offered to the pen each day calculated dry matter

intake. On the final day of the study, cattle were weighed individually and

shipped to Creekstone Packing Plant in Arkansas City, Kansas. Trained personnel

from West Texas A&M University took HCW and liver abscess data, and used

camera data to determine quality grade, yield grade, marbling score, LM area, and

backfat thickness at the 12th rib. Liver abscesses were classified using the methods

described by Brink et al. (1990). Dressing per cent was calculated using HCW

divided by the non-shrunk final BW, which was then used to calculated carcass-

adjusted BW from the HCW divided by the average DP from all three dietary

treatments and adjusting for 4% shrink (NRC, 1996). The carcass-adjusted


46

weights were then used to determine carcass-adjusted ADG, final shrunk BW,

initial BW, and G:F. The interim weights were used to calculate ADG, and G: F

ratio for the steers during each period.

Apparent Total Tract Nutrient Digestibility

During days 110 to 116, a digestibility assessment of the feed was

conducted. On day 110 bunks were cleaned at 0700 before feeding, and feces

samples were collected at 1600 that evening. During referred days, ort samples

were collected at 0700 and subtracted from the previous day offered diet. Feces

were also collected from at least three steers within each pen at 0700 and 1600h.

Approximately 10% of the orts were kept for analyses. Diet samples were

collected for all three treatments when cattle were fed at 0900 (composite

representing each experimental unit). At the end of the week, fecal samples were

composited by pen (ten samples per pen), 200 grams from each bag were mixed,

dried and a subsample was frozen (-20°C) for analyses. A similar composite was

made for the diet samples and ort samples. Ort samples collected that were greater

than 5% of total offered were kept for nutrient analyses. All samples were dried

for 72 hours in a 55°C forced air oven. Samples were ground in a 1 mm screen

Wiley Mill (Thomas Scientific, Swedesboro, NJ) and analyzed in laboratory for

DM, ash, NDF, ADF, AIA, and CP. A commercial laboratory (Servi-Tech,

Amarillo, TX), analyzed all fecal, diet and ort samples for starch and EE. The

AIA was utilized as an internal market (Van Keulen and Young, 1977) to

determine total fecal output. When the orts exceeded 5% of the total amount fed

daily, the AIA for each quantity was adjusted.


47

Laboratorial Analyses

Except for daily dietary sub-samples dried at 100°C, forced air oven for

24h (used to calculate DMI), all samples were pre-dehydrated at 55°C, forced air

oven for 72 h prior to analyses. Samples were ground through a 1-mm screen

(Wiley Mill; Thomas Scientific, Swedesboro, NJ) before nutrient analyses. Lab

analyses were adjusted to laboratorial dry matter (100°C for 24 hours) using

method 950.01 (AOAC, 1990). Organic matter was determined by subtracting the

residue from the ash process, which was processed oven (550°C for 4 hours)

following the method 942.05 (AOAC, 2005). Approximately 0.3 g of each diet,

fecal and ort sample, were placed into crucibles for N analysis (FP-200, Leco

Corporation, St. Joseph, MI) with the official method 992.15 (AOAC, 1995).

Neutral and acid detergent fibers were analyzed in sequence (Ankom 200,

Macedon, NY) where NDF procedure included thermo-stable amylase, sodium

sulfite and an acetone rinse (Van Soest et al., 1991). Starch and EE were analyzed

at a commercially certified laboratory (Servi-Tech, Amarillo-TX).

Feeding Behavior

On day 158-159, feeding behavior was analyzed for a 24h period.

Observations were recorded every 5 minutes, whether cattle were resting, active,

eating, ruminating, or drinking. Chewing activity was calculated by adding eating

and ruminating time. Because of the 24h period and 5-minute intervals, some data

points were missing due to human error (approximately 5%), so all behavior

results were expressed as daily percentage.


48

Statistical Analysis

Data were analyzed using the GLIMMIX procedures of SAS (SAS Inst.,

Inc., Cary, NC) with pen considered the experimental unit in a randomized block

design. The fixed effects of treatment were evaluated for intake, behavioral

evaluation, apparent total tract nutrient digestibility, growth performance and

carcass characteristics, with random effect of pen. Least square mean differences

were adjusted with a Tukey’s test, and degree of freedom bias was adjusted using

Kenward Rogers. Carcass data (USDA Quality Grade and liver scores) and

feeding behavior were reported on an individual basis, and the same model was

used as described previously. The data was non-Gaussian, so the Link function

was used for the analysis of the treatment effects. Linear and quadratic responses

(0, 25, and 50 g DM of yeast daily) and contrasts were evaluated. The two harvest

groups were considered a random effect. Significant differences were considered

if P ≤ 0.05 and tendencies if P > 0.05 and ≤ 0.10.

Results

Treatment Data

Throughout the course of the experiment, cattle were treated for both

lameness and respiratory issues. Two steers from the CTL treatment and one from

the LY treatment were removed early in the trial due to lameness. Another steer

was removed from the CTL treatment due to kidney failure. Respiratory disease

also hurt the feedlot, and seven were removed from the CTL group, 9 from the

LY treatment, and 10 from the HY treatment and were treated for respiratory

illness and removed from the study. Of the remaining steers, one from the HY, 3


49

from the LY and 3 from the CTL group were treated for respiratory issues and

remained in the experiment and were slaughtered at a local abattoir.

Growth Performance, Carcass Characteristics and Feeding Behavior

Growth performance, ADG, and G:F were not different between all three

treatments, shown in Table 2. There was a tendency (P = 0.08) for G:F to be

improved quadratically during the period of d0-183, and from d0-105 (P = 0.10)

for the LY treatment compared to the CTL and HY treatments.

Carcass characteristics and quality are noted in tables 3 and 4,

respectively. When evaluating carcass characteristics, similar to growth

performance, differences were not noted (P > 0.27). Between the three treatments,

no differences (P > 0.27) were noted in HCW (377 kg), dressing percent (63%),

yield grades (3.55), KPH percentage (2.02), marbling score (59), rib-eye area

(88.41 cm2), and backfat thickness (19 mm), as shown in Table 3. Although no

differences were observed in carcass characteristics, the inclusion of yeast in the

diet did result in some differences in carcass quality. There were no differences (P

= 0.11) in the amount of Prime carcasses in each treatment; however, Premium

Choice carcasses were increased linearly (P < 0.01) with increasing levels of yeast

in the diet. The CTL treatment had 33%, LY had 69%, and HY had 70% Premium

Choice carcasses. Choice carcasses decreased linearly (P = 0.05), where the CTL

had 34% Choice carcasses, while LY had 11% and HY had 9% Choice carcasses.

This shows the inclusion of yeast in the diet affects carcass quality, and using

yeast increases the number of carcasses produced that are of a high quality.


50

Liver score data for A-minus livers are showcased in Table 5. There were

very few carcasses with liver abscesses in the entire experiment, and there were

no differences between treatments as to which had more A minus scored livers.

The CTL group had 5 contaminated livers, and 2 A minus livers, the LY treatment

had 3 contaminated livers, 1 A plus, and 1 A minus liver, and the HY treatment

had 3 contaminated carcasses, and 4 A minus carcasses.

Feeding behavior is outlined in Table 6. No differences were noted

between treatments in terms of ruminating (P = 0.28), eating (P = 0.51), drinking

(P = 0.70), resting (P = 0.48) and chewing (P = 0.56) activity, which was a

combination of rumination and eating times. Cattle spent on average 8-9% of their

time eating, 10-12% ruminating, and 78-79% resting.


Apparent total tract digestibility was summarized in Figures 1 and 2. Other

than starch (P = 0.55), all nutrients experienced quadratic improvement (P < 0.01)

for the LY treatment over CTL and HY treatments. Although LY had greater

apparent total tract nutrient digestibility compared to both HY and CTL, HY also

had greater total apparent tract digestibility of all nutrients except for starch and

ether extract over the CTL treatment. In the fiber fractions, there was a quadratic

response for NDF to be improved over CTL and HY treatments (P < 0.01), and a

significant improvement (P < 0.01) of either yeast treatment compared to the CTL

treatment.


51

Discussion

The objective of this experiment was to evaluate levels of yeast and its

effect on the growth performance, carcass characteristics, apparent total tract

digestibility and feeding behavior of steers fed steam-flaked corn-based finishing

diets. The inclusion of yeast in the diet improved apparent total tract nutrient

digestibility of the steers, without causing a significant effect on growth

performance. A trend (P = 0.10) was observed in feed efficiency of the steers

from d0-183 fed the LY treatment. Although not statistically significant, the LY

treatment numerically improved growth performance during all periods of the

study. It would be expected LY had improved growth performance, because there

was improved digestibility of all nutrients but starch, which indicates cattle

derived more energy from the diet which could potentially improve growth

performance. The improved digestibility does not directly translate to improved

growth performance; the energy derived from the diet can become lean tissue or

fat tissue in marbling and back fat thickness. The use of yeast in the diet may

cause more marbling and fat deposition, which was observed in cattle receiving

higher carcass quality (P = 0.01) with increasing levels of yeast in the diet.

The moderate inclusion of yeast in the diet of beef steers fed steam-flaked

corn-based finishing diets numerically improved their feed efficiency. Other

studies observed similar results when yeast was included in the diet when cattle

were under stressful conditions (Cole et al., 1992, and Philips and VonTungeln

1985). Yeast and other DFM have been used as tools to improve the establishment

of intestinal microflora in young, stressed ruminants, improving the digestibility


52

of the diet (McAllister et al., 2011). Once it was observed DFM reduced the risk

of acidosis in ruminants, their use and continued research has been used to

improve cattle growth performance, specifically in natural programs.

The improved digestibility of nutrients in the current trial, specifically the

fiber fraction was consistent with other studies. In a review by McAllister et al.

(2011), it was reported the reason yeast improves fiber digestion by improving

cellulolytic bacterial growth, while simultaneously reducing the risk for acidosis

of feedlot cattle. Similarly, in this study, fiber fraction digestibility (Figure 2) was

significantly improved by moderate inclusions of yeast in the diet. As explained

by Jouany et al. (1998), yeast potentially provides an improved environment for

cellulolytic bacteria because it reduces the oxygen load in the rumen, improving

the environment for those microbes to grow and digest fiber fractions. This

improvement in fiber digestibility was observed by improved growth performance

for the moderate yeast level inclusions as well, albeit there was only a tendency

for improved growth in the current study

The improvement in CP digestibility is consistent with studies conducted

by Erasmus et al. (1992) and Dawson (1991), which observed improved ammonia

uptake with yeast inclusion in the diet. Improved CP digestibility may have been

due to improved microbial efficiency, with ammonia uptake to grow microbial

protein and activity (Erasmus et al., 1992). This improvement could improve

microbial protein production, ultimately increasing the protein and thus, amino

acids, available to the animal to use in production responses. However, in the

current study, LY treatment cattle had improved digestibility over HY treatment,


53

which is in contrast to other studies that conclude increasing levels of yeast

improved growth performance. The digestibility data is supported by the

numerical and tendency in gain efficiency improvements for LY steers over HY

and CTL steers. In most cases, the HY treatment was better than the CTL

treatment in terms of nutrient digestibility. The LY treatment might have been the

threshold for improved performance for yeast in the rumen environment, and

increasing past those levels has no benefit.

In a study by Yoon and Stern (1995), the inclusion of yeast in the diet of

dairy calves from 1% to 2% did not statistically increase the DMI from 6.2 to 6.4

kg daily, while the control diet only ate 5.6 kg daily. Similar to the current

experiment, there appeared to be a threshold at which the diet was the most

efficient. In a study by Swyers et al. (2014) included a Saccharomyces cerevisiae

fermentation product in a high concentrate diet (> 50% steam-flaked corn) at 2.8

g/head daily and observed the number of carcasses that grade USDA Choice, but

also observed a decreased ADG compared to Monensin treated animals. In a

study by Hinman et al (1998), the researchers included a Saccharomyces

cerevisiae fermentation product in a barley and potato residue finishing diet at 85

g/head daily for the first 28 days, and 28 g/head daily for the final 85 days of the

trial, and it improved steer ADG by 6.9% and feed efficiency by 4.5% throughout

the trial. In a dairy trial, Kung et al. (1997), cattle were fed diets including a

Saccharomyces cerevisiae product at 0, 10, and 20 g inclusion per head daily.

They observed cattle in the control group produced 36.4 kg of milk/day, and milk

production was 39.3 and 38.0 kg/d from the 10 and 20 g of yeast/day steers,


54

respectively (Kung et al., 1997). Similar to the current study, there appeared to be

a threshold at which the yeast was effective in the diet. In a study by Miller-

Webster et al. (2002), they compared two yeast products from two different

companies against a control diet, and discovered one of the yeasts left the rumen

at a higher pH average and higher microbial N/kg of dry matter digestibility. In a

study by Martin and Nisbet (1992) comparing two yeast strains, Asperigillus

oryzae and Saccharomyces cerevisiae, they observed improve total volatile fatty

acids and cell yield within the rumen. In this review by Martin and Nisbet (1992),

they were unable to determine if one treatment was more beneficial than the other

and that more research was needed, they were able to conclude improved

cellulolytic bacteria production for improved fiber digestion was a common factor

of the two DFM.

The lack of differences between the treatments when observing the

feeding behavior of the steers yeast showed yeast affects more digestive tract

kinetics rather than behavior. When cattle spend more time eating and ruminating,

they produce more saliva, which acts as a buffer in the rumen and reduces the risk

of acidosis, providing a better rumen environment for microbes. When improved

nutrient digestibility were observed in the current study, it was initially

hypothesized some of the results may have been due to increased chewing, which

can be related to a decrease in particles while providing more buffering solution.

However, when behavioral intakes were analyzed no differences were noted

between the three treatments. If there were to be differences in feeding behavior,

it might have similar effects to the product monensin, which is also included in


55

the diets at low levels while modifying the ruminal environment. In a review by

Gonzalez et al. (2012), monensin reduces meal size and frequency of meals,

reducing the starch load within the rumen, increasing ruminal pH averages. No

results such as this on feeding behavior were observed in the current study, which

might suggest yeast does not have the same modifying effects on the behavior of

cattle such as monensin, despite the fact both work by modifying the ruminal

environment.

Although the current study did not evaluate steer immune response or

growth response while under periods of stress, with improved digestibility

observed in the current study, animal might be able to derive energy more readily

during periods of stress because of improved ruminal environment. This

improvement in energy intake may help cattle overcome stressful periods and

improve better, not only during stressful phases of their lives, but also during the

subsequent finishing performance.

Natural program steers do not have the propensity to perform compared to

steers fed in conventional feeding programs as outlined by Wileman et al. (2014).

However, with the increased consumer concern as mentioned previously, having a

good knowledge on products considered available for natural production and their

methods of action would be beneficial for the beef industry. If a product is found

to improve performance naturally, it can be used as an alternative. While there are

doubts these products will ever work to the same efficiency as current growth

promoting technologies, any improvements over none at all are a benefit. The

current study had the tendency to improve gain efficiency while improving (P <


56

0.01) apparent total tract nutrient digestibility for all nutrients except starch (P =

0.55). The current study did not compare to conventional production methods,

however, feeding yeast at 25 g/head daily was better than not including yeast at

all in the diet. Similar to the current study, Moloney and Drennan (1994) observed

a tendency for improved gain efficiency in steers with no affect on carcass

characteristics. They came to the conclusion that yeast dietary interactions would

need to be further researched before making recommendations for the industry. In

steam-flaked corn-based finishing diets, the optimal inclusion of Saccharomyces

cerevisiae was 25 g/head daily.

Carcass characteristics were improved (P < 0.01) with increasing levels of

yeast on the number of Premium Choice carcasses produced. Carcass quality is

measured by rib-eye area, marbling, and appearance of the meat. An increase in

marbling and improvement in carcass quality may come from improved fat

deposition due to the improved fiber digestibility. Similar to the current study,

Swyers et al. (2014) observed an improvement in carcass quality with the

inclusion of Saccharomyces Cerevisiae fermentation product included in a steam-

flaked corn based finishing diet. It was also observed no difference between the

yeast and control diet in that study as well (Swyers et al., 2014). Other studies that

compared the inclusion of yeast to control diets experienced similar results with

no differences in carcass characteristics between treatments (Zerby et al., 2011).

Swyers et al (2014) hypothesized the inclusion of yeast coupled with the

improved quality grade of steers suggests cattle fed a yeast product are finished at

a lower end weight than monensin fed steers, resulting in fewer days on feed. This


57

was observed in the current study, with similar back fat thickness and marbling,

but improved quality as the yeast levels were increased. Although we did not

measure ruminal VFA concentrations, we can speculate yeast changed the

ruminal environment, to affect the carcass quality to improve carcass quality.

According to Smith and Crouse (1984), acetate supplies 70-80% of the acetyl

units for subcutaneous fat, while only supplying 10-25% in intramuscular adipose

tissue. Glucose, which is made in the liver from propionate, supplies 1-10% of the

acetyl for subcutaneous fat, while supplying 50-75% for the intramuscular or

marbling fat (Smith and Crouse, 1984). Including yeast in the diet could be the

reason for improved carcass characteristics due to the improved fiber digestibility,

as potentially more acetic acid could be converted to fatty acids.

Implications

In the diets of natural program steers fed steam-flaked corn-based

finishing diets, yeast improved overall apparent total tract nutrient digestibility,

which could potentially improve growth performance as compared to steers not

fed yeast products, although such expectation was not observed in the current

study. While growth performance results have been inconsistent, it is evident that

yeast does affect digestion. This coupled with data that suggests yeast improves

animal growth performance during periods of stress, might indicate cattle who

have been recently introduced to the feedlot could improve. Beneficial effect the

LY treatment had on apparent total tract nutrient digestibility of fiber leads an

inquiry about how it would affect the digestion of poorly digestible roughages

used during the adaptation phase of the feedlot phase. If yeast were to improve the


58

digestion of fibers from low roughage sources, cattle would be able to derive

more energy from these sources, and this supplementation could improve feedlot

profitability as they use less expensive roughage sources apart from alfalfa hay,

which is included in traditional adaptation phases. In conclusion, yeast

supplementation in the diets of beef steers improved nutrient digestibility at

moderate inclusions, but also positively affected carcass characteristics with

increasing yeast levels, while not negatively affecting growth performance.

Depending on the economics of carcass at the time of retail, it may be beneficial

for producers to include higher levels of yeast in the diet to improve carcass

quality and thus premiums for top-grade carcasses.


59

Table 1. Dietaryingredientsandnutritionalcompositionofdietsfedtonaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.

Item Live yeast, g/steer daily

0 25 50 Inclusion, % DM basis

Corn grain, Steam flaked

62.35 62.35 62.35

Sweet Bran 20.00 20.00 20.00 Corn Silage 10.00 10.00 10.00 Sorghum Silage 2.50 2.50 2.50 Supplement 2.00 2.00 2.00 Limestone 1.65 1.65 1.65 Urea 0.50 0.50 0.50 ABVista Premix Control

1.00 - -

ABVista Premix Low - 1.00 - ABVista Premix High - - 1.00

Analyzed Nutritional Composition NEm, Mcal/kg1 1.96 1.98 1.96 NEg, Mcal/kg1 1.32 1.32 1.30 CP, % DM 14.71 14.58 14.94 NDF, % DM 16.39 19.60 19.79 ADF, % DM 5.80 6.14 6.63 EE, % DM 3.00 3.40 3.20 Starch, % DM 49.60 47.30 48.40 1Calculated from growth performance data


60

Table 2. Effects of ABVista yeast (Saccharomyces cerevisiae) on growth performance of natural program beef steers fed a steam-flaked corn-based finishing diet.

Item Live yeast, g/steer

daily SEM1 P-Values

0 25 50 L2 Q3 Contrast Initial BW adj, kg 342 341 342 7.03 0.80 0.56 0.61 Final BW adj, kg 574 578 574 12.56 1.00 0.67 0.83 ADG, kg

Day 0-35 1.57 1.67 1.66 0.062 0.25 0.43 0.17 Day 0-70 1.44 1.49 1.44 0.047 0.97 0.37 0.63 Day 0-105 1.46 1.51 1.49 0.039 0.54 0.35 0.32 Day 0-140 1.34 1.34 1.36 0.039 0.81 0.76 0.96 Day 0-183 1.32 1.35 1.29 0.041 0.60 0.37 0.99 Day 0-End 1.19 1.21 1.18 0.033 0.76 0.49 0.93 Carcass Adj. 0-End4 1.18 1.20 1.19 0.036 0.89 0.65 0.73

DMI, kg/d

Day 0-35 7.42 7.46 7.48 0.064 0.46 0.89 0.48 Day 0-70 7.90 7.97 7.91 0.093 0.95 0.60 0.75 Day 0-105 8.31 8.28 8.33 0.093 0.84 0.77 0.98 Day 0-140 8.27 8.22 8.42 0.122 0.30 0.29 0.71 Day 0-183 8.36 8.32 8.50 0.255 0.44 0.46 0.76 Day 0-End 8.46 8.39 8.48 0.239 0.92 0.61 0.86

Gain:Feed Live Basis 0-35 0.211 0.224 0.222 0.008 0.29 0.38 0.18 Live Basis 0-70 0.182 0.187 0.181 0.005 0.90 0.34 0.70 Live Basis 0-105 0.176 0.183 0.178 0.004 0.53 0.10 0.18 Live Basis 0-140 0.163 0.163 0.160 0.004 0.62 0.74 0.79 Live Basis 0-183 0.158 0.163 0.152 0.004 0.20 0.08 0.81 Live Basis 0-End 0.141 0.144 0.139 0.003 0.58 0.17 0.83 Carcass Adj. 0-End4 0.139 0.143 0.140 0.003 0.93 0.33 0.57

1Standard error of the mean. 2Linear P-value 3Quadratic P-value 4Carcass-adjusted ADG and G:F from carcass-adjusted final shrunk BW, initial adjusted BW, and days on feed.


61

Table 3. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcasscharacteristicsofnaturalprogramsteersfedasteam-flakedcorn-baseddiet.

Item Yeast Treatment, g /steer

daily SEM1 P-Values

0 25 50 L2 Q3 Contrast Hot carcass weight, kg

376.4 378.7 376.4 5.34 0.99 0.67 0.83

Dressing percentage4

62.90 62.83 63.31 0.314 0.33 0.46 0.63

Yield grade 3.66 3.44 3.55 0.125 0.56 0.30 0.31 KPH Percent 2.02 2.02 2.02 0.023 0.80 0.89 0.77 Marbling score5 59.08 57.97 60.65 2.013 0.59 0.45 0.93 Rib-eye area, cm2 87.81 89.03 88.39 1.445 0.79 0.59 0.83 Back-fat thickness, mm 19.76 18.17 19.07 0.907 0.59 0.27 0.47 1Standard error of the mean 2Linear p values 3Quadratic p values 4Dressing percent calculated using non-shrunk final BW/HCW 530 = slight, 40 = small, 50 = modest, 60 = moderate, 70 = slightly abundant


62

Table 4. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcassqualityofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.

Item Yeast Treatment, g/steer daily

SEM1 P - Values

0 25 50 L2 Q3 Contrast Carcass Quality

Prime 27.72 11.23 18.91 0.077 0.37 0.15 0.11 Premium Choice 33.34 68.77 70.49 0.081 < 0.01 0.12 < 0.01 Choice 33.77 11.28 8.86 0.116 0.05 0.45 0.03 1Standard error of the mean 2Linear P-value 3Quadratic P-values


63

Table 5. EffectsofABVistayeast(Saccharomycescerevisiae)onliverscoresofnaturalprogrambeefsteersfedsteam-flakedcorn-basedfinishingdiets.

Item Yeast Treatment

g/steer daily SEM1 P - Values

0 25 50 L2 Q3 Contrast A Minus 1.60 0.63 3.29 0.027 0.50 0.28 0.92 Total4 2 2 4 - - - - A-Plus4 0 1 0 - - - - A4 0 0 0 - - - - Others-Contaminated4

5 3 3 - - - -

1Standard error of the mean 2Linear P - values 3Quadratic P – values 4No statistical estimate due to data not being able to converge. Not enough liver abscesses to determine a difference


64

Table 6. EffectsofABVistayeast(Saccharomycescerevisiae)onfeedingbehaviorofnaturalprogrambeefsteersfedsteam-flakedcorn-basedfinishingdiets.

Item Yeast Treatment, g/steer

daily SEM1 P -Values

0 25 50 L2 Q3 Contrast Time, % of 24

hours

Eating 8.47 8.32 9.04 0.652 0.51 0.55 0.78 Ruminating 11.51 11.67 10.27 0.958 0.28 0.43 0.58 Chewing 20.18 20.35 19.44 1.116 0.56 0.63 0.80 Resting 79.34 79.24 77.97 1.594 0.48 0.73 0.66 Drinking 0.25 0.29 0.28 0.059 0.70 0.68 0.60 Active 0.51 0.41 0.38 0.123 0.02 0.79 0.03 1Standard error of the mean 2Linear P - values 3Quadratic P - values


65

Figure 1. Effects of ABVista yeast (Saccharomyces cerevisiae) on apparent total tract nutrient digestibility of natural program beef steers fed steam-flaked corn-based finishing diets.

c cc

ba a

a

a

b bb

b

0

20

40

60

80

100

120

DryMatter OrganicMatter Starch CP EE

ApparentTotalTractDigestibility,%

Nutrient

0 25 50


66

Figure 2. Effects of ABVista yeast (Saccharomyces cerevisiae) on apparent total tract fiber fraction digestibility of natural program beef steers fed a steam-flaked corn-based finishing diet.

c

c

ba

a

a

bb

b

0102030405060708090100

NDF ADF Hemicellulose

ApparentTotalTractDigestibility,%

FiberFraction

0 25 50


67

CHAPTER III

COTTON BURRS AS ALTERNATIVE ROUGHAGE TO ADAPT BEEF STEERS TO STEAM-FLAKED CORN-BASED FINISHER DIETS

Abstract

Effect of cotton burrs as a roughage source during the transition of beef

cattle (hay to finisher diet) was evaluated on intake, ruminal characteristics,

nutrient digestibility, and feeding behavior. Ruminally cannulated steers (n = 6;

BW = 235 ± 81 kg) were assigned using a complete randomized design to 1 of 2

adaptation strategies: Alfalfa hay-based or cotton burrs-based. In both strategies,

roughage sources decreased as steam-flaked corn gradually increased. Steers were

fed ad libitum once daily, a series of six diets (7-d period each): wheat hay; 4

step-ups; and a finisher. In situ technique was used to assess ruminal fiber

degradability (substrate = wheat hay). Wireless rumen pH probes were used. A 3-

d spot fecal collection (twice daily, last 3 d of each period) and AIA were used to

estimate apparent total tract nutrient digestibility. Rumen fluid samples (0, 4, 8,

and 16 h after feeding) were taken (d-6 of each period) for VFA and NH3. Prior to

the adaptation strategies start, animals were fed add libitum wheat hay. Data were

analyzed using Glimmix procedure of SAS (wheat hay period used as a

covariate). Intake was not affected by adaptation strategies (P ≥ 0.16), except for

a tendency (P = 0.10) for steers adapted with alfalfa-strategy to ruminate more per

kg of NDF consumed during finisher diet, than those adapted with cotton burrs-

strategy. Steers fed cotton burrs-strategy showed lower ruminal pH average on

step-3 and finisher periods (5.62 and 5.51 vs. 6.04 and 5.83; P < 0.01 and P =


68

0.05, respectively) compared with alfalfa-strategy. A greater area of pH below

5.60 (200 vs. 15 min*pH; P < 0.01); lower ruminal NH3 concentration (5.1 vs. 8.8

mg/L; P < 0.01); and lower digestibility (OM, ADF, and hemicellulose; P ≤ 0.02)

during step-3 were also observed for steers fed cotton burrs-strategy compared to

alfalfa-strategy, respectively. However, cotton burrs-strategy steers showed

greater (P = 0.01) NDF digestibility during step-4; greater (P < 0.01) OM

digestibility during finisher diet; and lower acetate/propionate ratio (P = 0.04)

with a tendency (P = 0.08) to have greater propionate molar proportion during

step-2, compared to alfalfa-strategy steers. Ruminal fiber degradability was not

affected by adaptation strategies (P ≥ 0.36), neither was dietary starch

digestibility during common finisher (P = 0.73). Cotton burrs adaptation strategy

induced an improved ruminal fermentation environment during finisher diet,

although with riskier ruminal pH and rumination than alfalfa-strategy. Further

evaluation must consider cattle growth performance and economic aspects.

Key words: adaptation, alfalfa, cotton burrs, metabolism


69

Introduction

The period during which cattle are adapted from high roughage to high

concentrate diets is extremely important on their performance throughout the

finishing phase. The adaptation period can be extremely costly for the feedlot as

the usage of roughages, which have a low energy density, is extremely high,

accounting for approximately 50% of the total roughage consumed during the

feedlot phase (Mader et al., 1993). Because roughages are costly, reducing

reliance on them during the adaptation phase would be ideal. There are a few

available options to decrease dependence on roughages during the adaptation

phase. One option would be to decrease the days spent in the adaptation phase,

decreasing the time spent adapting to high concentrate diet, which could increase

the risk for acidosis as the rumen is abruptly exposed to high starch loads.

Another option feedlots have to reduce costs during the adaptation period is to use

byproducts from industries that utilize plant and plant products for their energy or

main product, often leaving a high fiber, low starch product behind. These

products have reduced cost because the main product was utilized, reducing costs

for the feedlot. However, the adaptation phase requires a low-starch fibrous

product to induce the ruminal microbial population acclimation from low to high

starch diet. The issue with using these byproducts is their effect on subsequent

performance and physiological response of the animals to the byproduct itself.

Some byproducts already widely used in the beef industry component of

adaptation strategies are wet corn gluten feed. A byproduct that has not been


70

widely researched in areas with high cotton production is cotton burrs, which are

the byproduct after the cotton milling process. The resultant product is high in

fiber, making it an ideal product for feedlots to use in place of expensive

roughage sources such as alfalfa hay. Unfortunately, it has not been widely

researched in the adaptation phase, rather usually used for maintenance cow diets.

The objective of this study was to research the use of cotton burrs as the roughage

source in adaptation diets in the feedlot and their effect on ruminal metabolic

variables of growing beef steers as they adapted to high concentrate diets.

Materials and Methods

All experimental procedures involving the use of animals were done in

accordance with Texas Tech University Animal Care and Use Committee

Protocol (T13079). The study was conducted at Texas Tech University Burnett

Center, located in Idalou, TX.

Treatments, design, and feeding

Six ruminally cannulated beef steers (235 ± 81 kg) were assigned to one of

two adaptation strategies using a complete randomized design. The two strategies

were either alfalfa hay or cotton burrs-based. The experiment consisted of six

periods of 7 d each, and each period consisted of increasing levels of steam-flaked

corn and decreasing levels of the respective roughage source. The first period was

a common wheat hay diet, the next four step-up diets, and a common finishing

diet, outlined in Table 7, and analyzed nutritional composition outline in Table 8.


71

Steers were fed ad libitum during each period, once daily at 1000 h. Steers were

housed individually in cement-slatted pens at the Texas Tech University Burnett

Center Pens. Each pen was equipped with automatic water troughs and individual

bunks.

Ruminal pH, VFA, and Ammonia Concentrations

On d-1 of each period, ruminal pH probes (DASCOR, Escondido, CA)

were calibrated in solutions of pH of 4.00 and 7.00, and adjusted to record

ruminal pH measurements every 6 minutes. Probes remained in the rumen

throughout each period and were removed at the end of d 7 of each period,

downloaded, recalibrated and reintroduced to the rumen for d 1 of each period,

prior to the daily feeding. This was repeated for all six periods. On d 7 of each

period, ruminal fluid was collected via the rumen cannulas and filtered through 4

layers of cheese-cloth, at 4, 8, 16, and 24 hours after feeding. All rumen samples

were immediately stored at -20°C for VFA and Ammonia analysis at a later date.

In order to analyze VFA from the ruminal fluid, samples were thawed and

centrifuged (10,000 ɡ; 10 min; 4oC). Four mL of the supernatant was treated

(deproteinized) with 0.8 mL of 25% metaphosphoric acid containing 2-

ethylbutyrate (0.2005 g in 100 mL; internal standard) (Erwin et al., 1961).

Individual VFA were analyzed in duplicate via gas chromatography (Shimadzu

GC-14A gas chromatograph).


72

Ammonia analysis was performed using a hypochlorite assay for

ammonia. Excess supernatant from the thawed VFA samples was mixed with 2.5

mL of phenol reagents and 2.0 ml of hypochlorite reagent. They were heated in a

water bath at 95°C for 5 minutes. They were then analyzed in a spectrometer

(Shimadzu UV-1800 Spectrophotometer) to analyze for ammonia in the rumen

samples.


Spot fecal collection occurred twice daily during the final 3 days of each

period. Acid insoluble ash (AIA) was the internal marker utilized to determine

digestibility of nutrients (Van Keulen and Young, 1977), by analyzing the AIA in

both the diets and feces to estimate total fecal output. When orts were greater than

5% of total offered, the concentration of AIA was adjusted for AIA concentration

in the orts. All samples, diets, orts, and feces were kept under refrigeration (-

20°C) until they could be analyzed for their respective nutrients. Frozen samples

were thawed, dried at 55°C in a forced-air oven, for 72 hours. Samples were then

ground in a Wiley Mill (Thomas Scientific, Swedesboro, NJ) to pass through a 1

mm screen.

Laboratorial Analyses

Daily dietary sub-samples were dried at 100°C in a forced-air oven for 24

h, to adjust for dry matter intake. All samples to be used in laboratory analysis

were pre-dehydrated at 55oC in a forced air oven for 48 to 72 h prior to analyses.


73

To correct for laboratorial dry matter, samples were dried at 100oC for 24 hours to

yield all nutrient values on a dry matter basis (method 950.01, AOAC, 1996). All

samples were ground through a 1-mm screen (Wiley Mill: Thomas Scientific,

Swedesboro, NJ) before laboratory nutrient analysis, except for in situ samples.

Neutral and acid detergent fiber fractions were analyzed in sequence, where NDF

was evaluated using thermo-stable amylase, sodium sulphite, final rinsing with

acetone, and subtracting remaining ash from residue (Van Soest et al., 1991). Ash

fractions were determined by ashing samples at 550°C in a furnace oven (4 h),

and organic matter was determined by subtracting from dry sample (method

942.05, AOAC, 1996). Nitrogen was analyzed by placing 0.3 g of each sample

into crucibles and run through LECO equipment (FP-200, Leco Corporation, St.

Joseph) (method 992.15, AOAC, 1995). Starch and ether extract were both

determined in a commercial certified laboratory (Servi-Tech, Amarillo, TX).

Ruminal In Situ Wheat Hay Degradability

Wheat hay collected from the same wheat hay diet fed to cattle during the

wheat hay period was used to accomplish ruminal fiber degradability evaluation.

Wheat hay samples were homogenized and ground in a Wiley mill (Thomas

Scientific, Swedesboro, NJ) to pass through a 2 mm screen. Approximately 5 g of

wheat hay was placed into separate triplicate nylon bags (10 x 20 cm: pore size 28

µm; Ankom Technology Co., Fairport, NY). The bags were placed into the rumen

via the cannula in reverse sequence at 0, 12, 24, and 48 hours post-feeding. Bags

were placed in the rumen d-6 through d-7 of each period and all removed at 0


74

hours. After removing from the rumen, all nylon bags were washed in the lab

(Food Technology building) by running under tap water until the water ran clear.

Following rinsing, nylon in situ bags were dried at 50ºC in a forced-air oven for

72 h. The residue in each nylon bag was analysed for dry matter (100oC in a

forced-air oven for 4 h), organic matter (ash oven, 550oC, for 4 h), neutral

detergent fiber, and acid detergent fiber (analyzed in sequence) as described prior

in the laboratorial analysis section. Apparent disappearances of dry matter,

organic matter, NDF, and ADF were calculated using the following equation:

Disappearance, % = {1-[(residue, g × nutrient % in residue) / (sample, g ×

nutrient % in sample)]} × 100.

Feeding Behavior

On d 4 to 5 of each period, a 24h behavior of each animal was conducted.

Visual observations by trained personnel were taken every 5 minutes for the

following behaviors: eating, drinking, resting while standing up or laying down,

ruminating while standing up or laying down and active. From this total chewing

time, which was time spent eating plus time spent ruminating, total resting time,

which was time spent resting while standing up and laying down, and total time

spent chewing and ruminating per unit of NDF intake in the diet were also

calculated. Time spent on each activity was shown as a percentage for each day.

The intake of NDF was corrected for orts nutrient composition.


75

Statistical Analyses

Data were analyzed using the GLIMMIX procedures of SAS. The initial

wheat hay period was used as a covariate for all variables. The effects of cotton

burrs versus alfalfa hay based adaptation strategies were evaluated for intake,

feeding behavior, apparent total tract nutrient digestibility, ruminal pH and VFA

variables, and ammonia concentrations in the rumen. For intake measures, day

was treated as a repeated measure. For ruminal VFA, ammonia concentration and

pH, time of day was treated as a repeated measure. Covariance structures for

repeated measures were chosen based on smallest Akaike’s information criterion

and Bayesian information criterion. The general degrees of freedom procedure

Kenward-Rogers was used to adjust for any bias on standard errors caused by

multiple terms in the random statement. Models included the random effect of

steer within treatment. Significant differences were considered if P ≤ 0.05 and

tendencies if 0.05 < P ≤ 0.10.

Results

Dry Matter Intake

The DMI was evaluated daily for each steer. The intake in kg/day was

evaluated for all six periods. No differences were noted between the two

strategies for all six periods (Table 9).


76

Ruminal pH, VFA, and Ammonia Concentration

The averages of ruminal pH during the six period and the respective pH

variables are shown in Tables 9, 10 and Figure 3. The ammonia concentrations

observed within the rumen are found in tables 9, 10, and Figure 4. The cotton

burrs strategy had lower ruminal pH averages during steps 2 (P = 0.01), step 3 (P

< 0.01), and finisher diet (P = 0.05), with averages of 5.66, 5.62 and 5.51 vs 5.78,

6.04, and 5.83, respectively. Despite the fact rumen pH average was lower for the

cotton burrs strategy for steps 2, 3, and the finisher diet, the time and area spent

below pH 5.60, which is considered to be sub-acute acidosis, only during step 3

did the cotton burrs strategy spend more time below 5.60, as shown in Table 10.

During step 3, cattle spent 599 min/d under the pH of 5.60 compared to 160 min/d

in the alfalfa hay strategy. The area spent below 5.60 was also significant in step 3

(P < 0.01) for the cotton burrs strategy compared to the alfalfa hay strategy (200

min*pH vs 15 min*pH respectively). There was a tendency (P = 0.07) during the

finisher step that cotton burrs adapted cattle spent more time below a rumen pH of

5.0, 119 min/d vs. 5 min/d, compared to alfalfa hay-strategy cattle. Maximum

ruminal pH was greater (P = 0.05) during the finishing phase for alfalfa over the

cotton burrs strategy. Other ruminal pH variables such as maximum pH,

minimum pH and pH variance were not different between the treatments.

Ammonia concentrations were lower in steps 1 (P = 0.02) at 11.27 vs 18.74

(mg/L), and step-3 (P < 0.01) at 5.06 vs. 8.82 (mg/L) for the cotton burrs strategy

compared to alfalfa hay strategy, respectively. There was a tendency (P = 0.10)


77

during step-4 for cotton burrs strategy to show have a lower ammonia

concentration (5.00 vs 6.75 mg/L).

Ruminal VFA molar proportion results are shown in tables 11 and 12,

showcasing wheat hay through to the finishing phase for acetate: propionate ratio,

acetate, propionate, butyrate, and total VFA in mmol/L observed in the rumen at

proportion of VFA in the rumen at mmol/100 mmol of the total VFA. In step 1,

molar propionate proportions were greater (P = 0.03) for alfalfa versus cotton

burrs strategy (23 versus 20.19 mmol/100 mmol). Isobutyrate molar proportions

were greater (P < 0.01) for alfalfa hay strategy (0.81 vs 0.49 mmol/100mmol)

over the cotton burrs strategy. During step 2, the acetate to propionate ratio had a

tendency (P = 0.09) to be greater for alfalfa at 1.76 vs. 1.35 for the cotton burrs

strategy. Propionate molar proportions were lower (P = 0.08) for the alfalfa hay

strategy at step 2 (29.41 vs. 34.90 mmol/100mmol). Isobutyrate molar proportions

had a tendency to be lower (P = 0.09) during step 2 (0.42 vs 0.54 mmol/100

mmol). During step 4, valerate molar proportions were lower (P = 0.04) for the

alfalfa hay strategy (1.52 vs. 2.39 mmol/100 mmol) compared to the cotton burrs

strategy. This continued during the finishing phase (P = 0.03) at 1.50-mmol/100

mmol during the alfalfa hay strategy versus 2.77 mmol/100 mmol for the cotton

burrs strategy.


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The apparent total tract digestibility of the nutrients starch, EE, CP, NDF,

ADF, hemicellulose, dry matter and organic matter are shown in Tables 13 and

14. Dry matter digestibility had a tendency (P = 0.08) to be greater in step-1,

73.79 vs. 60.13% for the alfalfa strategy compared to the cotton burrs strategy.

There was a tendency (P = 0.06) during the finishing phase for the cotton burrs

strategy to have improved digestibility (76.17% vs. 70.65%) over alfalfa hay

strategy. Organic matter had a tendency to be greater in the alfalfa hay strategy (P

= 0.08) in step 1 (75.80% vs. 61.68%). During the finishing phase for organic

matter digestibility, the roles were switched and the cotton burrs had a greater

digestibility (P < 0.01) at 77.63 vs. 72.02% over the alfalfa hay adaptation

strategy. The NDF digestibility was greater (P = 0.01) for the cotton burrs

strategy than the alfalfa hay strategy during step 4. The ADF digestibility in the

alfalfa hay strategy had a tendency to be greater during (P = 0.06) step-1 (54.81

vs. 22.65%), and greater (P < 0.01) during step-3 (37.68 vs. 15.18%,

respectively). Hemicellulose was also more digestible (P = 0.02) during step 3 for

the alfalfa hay strategy (42.76 vs. 32.27%) compared with cotton burrs strategy.

Crude protein showed greater digestibility (P = 0.03) during step 1 for alfalfa hay

(78.50 vs. 59.47%) compared with cotton burrs strategy. The same pattern tended

(P = 0.07) to be repeated in step 2 (69.94 vs. 64.53%). Starch digestibility was

similar between both treatments except step 1, where alfalfa hay strategy had

greater (P = 0.02) starch digestibility at 98.26 vs. 92.76% compared with cotton


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burrs strategy. For EE, steer fed during step 1 showed greater digestibility in the

alfalfa hay (P < 0.01) at 95.57 vs. 93.31%.

Ruminal In Situ Wheat Hay Degradability

In situ degradability is shown in Tables 15 to 19. No interaction between

treatment and time (P ≥ 0.13), neither main effects of treatment (P ≥ 0.36) was

observed. In all cases and during all steps, as incubation time increased, the

amount of material degraded also increased (P < 0.01).

Feeding Behavior

Feeding behavior is shown in Tables 20 and 21. No differences in total

resting or ruminating behavior were observed (P > 0.05). During step 2, the

alfalfa strategy cattle spent more (P < 0.01) time ruminating while standing up,

and more total time (P = 0.05) resting than the cotton burrs strategy cattle. Cotton

burrs strategy cattle spent more (P = 0.03) time being active during step 2 than the

alfalfa strategy adapted steers. During step 3, the alfalfa strategy steers spent more

time (P = 0.02) ruminating while standing up than cotton burrs strategy steers.

During steps 4, the alfalfa strategy steers spent less time (P = 0.03) ruminating

while laying down than the cotton burrs strategy steers, and had a tendency (P =

0.08) to spend more total time resting during the day than the alfalfa adapted

cattle. During the finishing step, the time spent ruminating per unit of NDF had a

tendency (P = 0.10) to be lower for cotton burrs strategy compared to alfalfa hay

at 243 min/kg daily of NDF as compared to 197 min/kg daily of NDF intake.


80

Discussion

Adapting cattle to high concentrate diets efficiently to improve growth

performance while avoiding nutritional health issues is very important. During the

adaptation period cattle were adapted from a wheat hay diet to a 65% steam-

flaked corn-based finishing diet, using cotton burrs or alfalfa hay as a roughage

source. The DMI between the two strategies did not differ during the six periods.

One of the issues with adapting cattle is not only being concerned about the

ruminal microbiota adaptation effects, but also factors that may trigger animal

satiety, regardless of by gut fill or ruminal chemical receptors (Church, 1993). By

increasing the time spent to adapt cattle to finishing diets, gut fill and eventually

chemical receptors can determine intake, reducing the intake variation observed

when cattle are adapted quickly (Choat et al., 2002). Adapting cattle over longer

periods of time may attribute to less inconsistency in intake. The ruminal pH

variables may not have varied as much as other studies because steers were

adapted over a period of 6 weeks rather rapid adaptation has more effect on the

ruminal pH variance compared to slower, more controlled adaptations (Bevans et

al., 2005).

According to Hill et al. (2000), cattle fed diets made primarily of cotton

burrs had decreased intakes compared to cattle grazing grass for the first ten days

as cattle adjusted to the physical aspect of cotton burrs. This may not be the case

in current study, and the lack of difference in intakes showed cattle

physiologically accepted the cotton burrs as an acceptable ingredient in the diet


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and did not negatively react to the cotton burrs, when compared to alfalfa hay.

The cotton burrs adaptation strategy appeared to have a lower average rumen pH

and more consistent day-to-day average pH than the traditional alfalfa hay

strategy. While this may be viewed as a negative aspect because a large part of

adapting cattle to finishing diets is to avoid ruminal acidosis and the resultant

liver abscesses, other aspects of the ruminal environment that were measured

portray this as a potentially positive result of feeding cotton burrs rather than

alfalfa hay during adaptation strategies. While the cotton burrs strategy steers had

a lower average ruminal pH, only during step 3 did the steers spend more time

below a ruminal pH of 5.6 than steers fed the alfalfa hay strategy. Bevans et al.

(2005) observed lower ruminal pH could be due to increased VFA loads as cattle

were adapted to high concentrate diets rather than lactic acid production,

especially if diet increases were done over longer periods of time. Throughout the

finisher diet, which was common between both strategies, the cotton burrs

strategy tended to spend more time below a pH of 5.0 than the alfalfa hay

strategy. This reduction in ruminal pH could be due to an increase in VFA

present in the rumen from improved access to nutrients. Fernando et al. (2010)

observed an increase in anaerobic and amylolytic bacteria within the rumen as the

concentrate in the diet increased during the adaptation phase. As concentrate in

the diet increases, Fernando et al. (2010) observed a decrease in bacterial

populations that could digest both fibre and starch, due to decreased ruminal pH

average. This would help in the shift of microbial population to more amylolytic

bacteria (Fernando et al., 2010). The reduction in ruminal pH even in the finishing


82

phase for the cotton burrs strategy steers may have been due to an increased rate

of VFA production which was greater than the absorption, if the animal can make

overcome this drawback, where more energy become available (Anderson et al.,

2015). This is potentially the case because although it was a lower average

ruminal pH, the cotton burrs strategy steers did not spend much more time under

acute or even sub acute acidotic conditions compared to alfalfa hay strategy.

Despite the fact no differences in DMI were observed, the ruminal pH variables

were affected by changes in the diet composition, as well as the apparent total

tract nutrient digestibility. As the rumen was adapted to the high concentrate diets,

digestibility of the diets in either strategy transitioned from better apparent

digestibility in step 1 for the cotton burrs, to better digestibility for alfalfa hay

strategy in step 3. As the diet changes and starch becomes the main ingredient in

the diet, the ruminal microbial population becomes less diverse, which should

ideally make the two strategies become more similar in all aspects as the finishing

diet is approached (Fernando et al., 2010, Anderson et al., 2015). It would be

anticipated that alfalfa hay would have better apparent digestibility compared to

cotton burrs because it is a high quality roughage source. The current study was

designed to observe the effect of cotton burrs and evaluate its effect against a

known adaptation strategy such as alfalfa hay. The reduction in ruminal pH and

the increase in organic matter digestibility in the finishing diet of those steers

adapted using the cotton burrs strategy suggests the cotton burrs strategy had

some underlying effects on steer performance and microbial population as

compared to the alfalfa hay strategy. Although a lower ruminal pH was observed,


83

which is a cause of concern of ruminal acidosis during the finishing phase of

steers, this ruminal pH may be what the steer is acclimated to, and further

finishing growth performance analysis would have to be researched before

drawing a more abroad implication. That being said, with the increase in organic

matter digestibility, some of it may be attributed to the ruminal digestibility,

which would decrease ruminal pH with more starch being fermented and acids

being produced within the rumen, causing that reduction in ruminal pH average,

while supplying ruminal microbiota with more substrate for development. Current

data pairs well with the ammonia, as lower ruminal ammonia levels are noted in

steers adapted using the cotton burrs strategy diet during steps 1 and 3, and a

tendency during step 4. A reduction in ammonia concentration within the rumen

suggests that ruminal microbiota utilized more efficiently the N available from

diet, (Moloney and Drennan, 1994). While microbes are utilizing the protein

within the diet, the improved digestibility of organic matter would be explained

because microbes are utilizing both (energy and protein) to induce ruminal

development, and at same time have a stable ruminal environment. Although the

cotton burrs strategy was seen negatively in terms of ruminal pH variables, it

could be an indication that cotton burrs better equips the rumen for the high starch

load diets and may help improve growth performance and efficiency of the rumen

microbial synthesis, and thus the animal under feedlot conditions. Further

research is needed to confirm finishing growth performance after the adaptation

phase.


84

Ruminal in situ degradation was not different between the two strategies

for any of the nutrients evaluated during all six periods. As noted above, no

differences between the two strategies were positive because it meant cotton burrs

were just as capable as alfalfa hay in the adaptation phase. In situ degradation

evaluated the fiber degradability of wheat hay during all six periods. Not

surprisingly, all fiber fractions endured increased degradation as the time

increased from 0 to 48 hours. Due to the fact it was a common fiber source

utilized to analyze the rumen degradability, any major differences in the rumen

environments between the two strategies would have been noted in how well fiber

was degraded. If the ruminal environments had changed as a result of the different

ingredients, it was hypothesized the ability of the rumen to degrade the fiber

fractions would have been different, because cellulolytic bacteria play such an

important role in the degradation.

Feeding behavior is another indicator of how cattle respond to new diets.

The physical activity of chewing by the animal to induces feedstuff nutrient

utilization by the microbiota digestion (Beauchemin et al., 1994). Increasing

chewing time has increased ruminal degradation and increased fiber digestion

(Beauchemin et al., 1994). Unfortunately, differences in chewing or ruminating

times were not documented in current study, showing digestibility and ruminal

degradability occurred due to chemical and microbial response of the rumen,

rather than induced by changes in behavioral perception of the adaptation

strategies. Despite the fact some studies have observed cattle do not always


85

respond well to cotton burrs added to the diet (Hill et al., 2000), the cattle in

current study did not show any apparent effect on intake and showed adequate

adaptation patterns throughout the feeding periods. The measurement of cattle

chewing, ruminating, and eating activities help to better understand potential

positive effects due to chewing on buffering in the rumen (saliva production), and

differences between behaviour might also explain some of the differences noted

in pH and VFA levels within the rumen. While there were slight differences in

times spent ruminating while lying down or standing up between the two

strategies, there were no differences between total time spent ruminating or

chewing. As suggested above in the discussion about the ruminal pH variables,

the response in the rumen was chemical rather than a physiological response to

the diet. That being said, more time was spent ruminating per unit of NDF intake

during the finishing diet for the cattle adapted through the alfalfa strategy. This

tendency for an increase in rumination activity may have lasting effects

throughout the growth performance phase as cattle combat the effects of low

ruminal pH. Increased chewing time increases saliva production, which increases

ruminal pH because of its buffer like properties (Beauchemin et al., 2005). These

results are a benefit of alfalfa hay over the cotton burrs strategy. However, as

observed in earlier periods, the rumen of cattle adapted in the cotton burrs strategy

had lower average ruminal pH during a couple steps, suggesting while the ruminal

pH was low, it was not in harmful acidotic levels for the rumen. The decreased

chewing time and decreased ruminal pH, while lower, may not negatively impact


86

growth performance, as ruminal microbiota that produce propionate may perform

better at lower ruminal pH and have a more stable rumen environment.

Differences in VFA variables between the two adaptation strategies were

observed throughout many of the steps in current study. During step 1, molar

proportions of propionate were greater for the alfalfa strategy over the cotton

burrs strategy. Propionate production results from starch, and growth of

microorganisms, and it is necessary for glucose production for the animal through

gluconeogenic pathways (Bergman et al., 1990). Propionate is largely taken up by

the liver to be converted to glucose, and used as an energy source (Bergman et al.,

1990). The improved propionate molar proportion during step-1 may be due to the

increased starch in the diet. In addition, alfalfa hay is a high quality roughage

source and provides energy that cotton burrs perhaps does not possess. A

tendency for propionate improved during step 2 may have been a result of

microbes in the rumen that were acclimated to getting as much starch out of the

inclusion of the steam-flaked corn, and were more able to produce propionate

with the same materials as the alfalfa hay strategy steers as the levels of roughage

decreased. Isobutyrate molar proportions were greater during step 1 for the alfalfa

hay strategy and lower during step 2 for the alfalfa hay strategy. Differences and

the effect of isobutyrate on the rumen were not consequential, as the volatile fatty

acids other than butyrate, acetate and propionate make up less than 5% of the total

acids in the rumen (Bergman et al., 1990). The acetate to propionate ratio had a

tendency to be higher for the alfalfa hay strategy than the cotton burrs strategy,


87

which worked perfectly in line with the increased propionate proportion with the

cotton burrs strategy. Valerate molar proportions were greater during step 4 and

the finisher period for the cotton burrs strategy, however, because they represent

less than 5% of total VFA production, it may not be of concern. The results from

the VFA show that even though cattle were adapted using a lower quality

roughage source such as cotton burrs, ruminal VFA molar proportions were not

harmed and cattle were able to efficiently degrade and utilize the roughage

source, as noted with no differences in total VFA ruminal concentration

throughout any of the six periods.

Implications

Some of the current challenges of adapting cattle to high concentrate diets

using traditional roughage sources can be alleviated using cotton burrs. Cotton

burrs are widely available in the southern United States and appear to be able to

provide an alternative for feedlot producers adapting cattle to high concentrate

diets. Cotton burrs may be a cost effective alternative strategy that does not

negatively affect ruminal metabolic variables. Some care does need to be taken

with feeding the cotton burrs as the ruminal pH of those cattle fed cotton burrs

was lower and might lead to acidotic conditions if not monitored carefully.

However, with proper management and feeding techniques this lower ruminal pH

during the early periods of adaptation may acclimate the rumen more effectively

to high concentrate loads, as finishing diet apparently digestibility increased. The

cotton burrs strategy appears to provide a better ruminal fermentation


88

environment than the alfalfa adaptation strategy, albeit with a riskier average

ruminal pH pattern. When considering cost of the roughage, cotton burrs might

provide an alternative if available at a reasonable cost. Further research is

required to further determine the effect of cotton burrs during the adaptation phase

on cattle growth performance, economic value and resultant carcass

characteristics during the finishing phase.


89

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98

Table 7. Dietary composition of adaptation diets using cotton burrs or alfalfa hay as a roughage source. Adaptation periods Ingredient, % DM Wheat Hay Step 1 Step 2 Step 3 Step 4 Finisher Alfalfa Hay Strategy Wheat Hay 98.50 - - - - - Mineral 1.50 - - - - - Steam Flaked Corn - 30.68 38.18 45.68 53.18 60.68 Alfalfa Hay - 30.00 22.50 15.00 7.50 - Cotton Burr - - - - - - Corn Silage - 7.50 7.50 7.50 7.50 7.50 Sorghum Silage - 7.50 7.50 7.50 7.50 7.50 WCGF, Sweet Bran - 15.00 15.00 15.00 15.00 15.00 TTU Supplement - 2.00 2.00 2.00 2.00 2.00 Cottonseed Meal - 1.20 1.20 1.20 1.20 1.20 Tallow - 3.50 3.50 3.50 3.50 3.50 Limestone - 1.78 1.78 1.78 1.78 1.78 Urea - 0.84 0.84 0.84 0.84 0.84 Cotton Burrs Strategy Wheat Hay 98.50 - - - - - Mineral 1.50 - - - - - Steam Flaked Corn - 30.68 38.18 45.68 53.18 60.68 Alfalfa Hay - - - - - - Cotton Burr - 30.00 22.50 15.00 7.50 - Corn Silage - 7.50 7.50 7.50 7.50 7.50 Sorghum Silage - 7.50 7.50 7.50 7.50 7.50 WCGF, Sweet Bran - 15.00 15.00 15.00 15.00 15.00 TTU Supplement - 2.00 2.00 2.00 2.00 2.00 Cottonseed Meal - 1.20 1.20 1.20 1.20 1.20 Tallow - 3.50 3.50 3.50 3.50 3.50 Limestone - 1.78 1.78 1.78 1.78 1.78 Urea - 0.84 0.84 0.84 0.84 0.84


99

Table 8. Analyzed nutritional composition of adaptation diets using cotton burrs or alfalfa hay as a roughage source. Adaptation periods Nutrient, % DM

Wheat Hay

Step 1 Step 2 Step 3 Step 4 Finisher

Alfalfa Hay Strategy Starch 1.50 28.60 30.70 41.40 44.10 41.60 Ether Extract 1.10 6.10 6.30 5.90 7.20 7.40 NDF 60.75 28.48 25.91 23.06 20.57 17.35 ADF 32.51 15.17 13.60 11.16 8.69 6.43 Hemicellulose 28.24 13.31 12.31 11.90 11.88 10.91 Crude Protein 9.55 16.40 16.33 14.63 16.02 15.67 Ash 8.18 8.35 7.94 5.98 5.70 6.30 Cotton Burrs Strategy Starch 1.50 26.20 29.70 37.70 42.40 41.60 Ether Extract 1.10 5.30 6.20 6.60 7.30 7.40 NDF 60.75 29.09 26.49 22.87 19.92 17.35 ADF 32.51 16.55 14.43 11.06 8.84 6.43 Hemicellulose 28.24 12.54 12.06 11.80 11.07 10.91 Crude Protein 9.55 14.44 14.43 17.34 15.57 15.67 Ash 8.18 10.22 8.65 7.53 6.21 6.30


100

Table 9. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on dry matter intake, ruminal parameters-Wheat Hay, Step 1 and 2. Wheat Hay Step 1 Step 2 Adaptation

Strategy SEM1 P-

Value Adaptation

Strategy SEM1 P -

Value Adaptation

Strategy SEM1 P -

Value Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM

30.00 30.00 22.50 22.50

DMI, kg/d 4.86 4.43 0.440 0.16 5.85 6.33 0.240 0.24 7.04 7.45 0.547 0.36 Ruminal pH Parameters

Average 6.58 6.34 0.082 0.11 5.86 5.94 0.098 0.62 5.78 5.66 0.030 0.01 Variance 0.01 0.04 0.048 0.81 0.10 0.07 0.014 0.16 0.13 0.11 0.026 0.71 Maximum 6.80 6.64 0.080 0.24 6.48 6.57 0.127 0.69 6.46 6.31 0.052 0.11 Minimum 6.30 5.89 0.151 0.13 5.27 5.37 0.097 0.64 4.79 5.07 0.209 0.42 Time Below 5.6, min/d 0.02 21.40 9.132 0.17

318.86 320.86 124.370 0.99

452.47 664.10 91.248 0.39

Area below 5.6, min*pH 0.00 1.53 0.575 0.13

61.60 45.04 20.923 0.63

104.17 162.13 28.652 0.24

Time Below 5.0, min/d 0.00 0.00 0.000 0.00

0.80 0.00 0.526 0.30

11.57 32.99 22.306 0.59

Area below 5.0, min*pH 0.00 0.00 0.000 0.00

0.00 0.00 0.00 0.00

6.33 2.84 4.006 0.62

Ammonia Concentration Ammonia (mg/L) 1.68 1.73 0.923 0.34 18.74 11.27 1.403 0.02 10.45 10.50 1.947 0.99 1Standard error of the mean


101

Table 10. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on dry matter intake, ruminal parameters-Steps 3 and 4, Finisher. Step 3 Step 4 Finisher Adaptation

Strategy SEM1 P - Value

Adaptation Strategy SEM1

P - Value


P - Value

Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM

15.00 15.00 7.50 7.50

DMI, kg/d 7.43 7.87 0.233 0.22 7.32 7.71 0.526 0.39 7.85 7.89 0.953 0.38 Ruminal pH Parameters

Average 6.04 5.62 0.049 <0.01 5.80 5.79 0.114 0.98 5.83 5.51 0.083 0.05 Variance 0.105 0.133 0.049 0.72 0.104 0.094 0.026 0.82 0.102 0.118 0.029 0.70 Maximum 6.44 6.52 0.091 0.31 6.45 6.37 0.045 0.33 6.48 6.20 0.062 0.05 Minimum 5.30 4.65 0.308 0.22 5.09 4.84 0.229 0.54 5.18 4.86 0.117 0.12 Time Below 5.6, min/d 159.59 599.33 103.29 0.10

416.01 376.84 162.13 0.88

356.74 804.46 174.73 0.13

Area below 5.6, min*pH 15.16 200.42 24.626 <0.01

133.09 71.78 60.386 0.53

97.35 258.11 66.550 0.16

Time Below 5.0, min/d 0.00 59.73 5.896 0.02

41.06 0.00 29.17 0.35

4.86 119.90 39.635 0.08

Area below 5.0, min*pH 5.50 6.95 10.600 0.93

4.85 0.00 2.795 0.24

2.47 13.31 3.126 0.15

Ammonia Concentration Ammonia (mg/L) 8.82 5.06 1.019 <0.01 6.75 5.00 0.543 0.10 7.01 5.16 0.814 0.21 1Standard Error of the mean


102

Table 11. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on ruminal volatile fatty acid profile-Wheat Hay, Step 1 and 2. Wheat Hay Step 1 Step 2 Adaptation

Strategy SEM1 P -Value


P - Value


P -Value


30.00 30.00 22.50 22.50

Total, mmol/L 82.018 84.021 5.5304 0.81 102.280 103.790 6.5647 0.88 139.940 112.480 11.7390 0.12 C2:C3 3.812 3.744 0.0418 0.27 2.583 2.877 0.2215 0.44 1.757 1.350 0.1120 0.09

Molar Proportion, mmol/100 mmol Acetate 69.997 70.586 0.4022 0.33 58.656 58.575 1.6458 0.97 48.169 48.259 2.1594 0.98 Propionate 18.357 18.934 0.1110 <0.01 23.915 20.187 0.6865 0.03 29.411 34.901 1.705 0.08 Butyrate 9.224 8.735 0.2192 0.11 14.253 18.078 1.9245 0.23 14.872 17.998 2.9765 0.36 Isobutyrate 0.765 0.552 0.0619 0.02 0.811 0.490 0.06195 <0.01 0.418 0.541 0.04195 0.09 Valerate 0.646 0.651 0.0469 0.94 1.506 1.665 0.2108 0.62 1.365 1.303 0.1760 0.82 Isovalerate 0.880 0.671 0.1109 0.25 0.995 0.868 0.1371 0.55 1.468 1.298 0.4379 0.78 1Standard Error of the Mean


103

Table 12. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on ruminal volatile fatty acid profile-Step 3, 4 and Finisher. Step 3 Step 4 Finisher Adaptation



P - Value


P -Value


15.00 15.00 7.50 7.50

Total, mmol/L 133.930 147.760 11.200 0.44 123.920 117.590 4.2833 0.31 136.250 134.560 8.0015 0.88 C2:C3 2.263 0.973 0.639 0.21 1.237 1.098 0.0997 0.38 0.996 0.984 0.0973 0.83

Concentrations, mmol/100 mmol Acetate 49.076 44.539 3.940 0.52 49.027 47.474 1.5243 0.51 43.357 44.062 3.1076 0.88 Propionate 36.203 39.207 5.406 0.71 40.267 43.304 2.0364 0.35 45.169 45.626 3.4058 0.91 Butyrate 13.157 12.101 1.495 0.64 7.571 5.758 1.0173 0.27 5.920 7.712 1.3885 0.42 Isobutyrate 0.368 0.204 0.137 0.45 0.229 0.198 0.0470 0.67 0.148 0.167 0.0812 0.88 Valerate 1.320 1.562 0.232 0.50 1.523 2.395 0.1956 0.04 1.497 2.774 0.2669 0.03 Isovalerate 1.435 0.828 0.188 0.08 1.262 0.990 0.1644 0.28 1.570 2.002 0.5453 0.54


104

Table 13. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on apparent total tract nutrient digestibility-Wheat Hay, Step 1 and 2.

Wheat Hay Step 1 Step 2

Adaptation

Strategy SEM1 P -

Value Adaptation

Strategy SEM1 P -

Value Adaptation

Strategy SEM1 P -

Value Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton

Roughage Inclusion, % DM

30.00 30.00 22.50 22.50

Apparent Total Tract Digestibility, % DM basis Dry Matter 66.58 67.96 0.657 0.21 73.79 60.13 4.146 0.08 67.21 67.43 1.293 0.91

Organic Matter 68.85 70.41 0.718 0.20

75.80 61.68 4.280 0.08

68.93 70.09 1.147 0.51

NDF 70.97 72.82 0.524 0.07 51.64 38.50 9.319 0.38 36.31 39.20 4.191 0.65 ADF 71.11 73.03 0.901 0.21 54.81 22.65 11.893 0.06 35.32 32.22 3.807 0.60

Hemicellulose 70.69 72.71 0.194 <0.01 54.29 33.18 7.794 0.13 37.66 46.40 4.754 0.26 Crude Protein 57.95 61.31 1.075 0.09 78.50 59.47 3.817 0.03 69.94 64.53 1.586 0.07 Ether Extract 50.77 49.38 1.256 0.48 95.57 93.31 0.412 0.10 93.84 94.97 0.454 0.15

Starch 97.97 97.94 0.080 0.81 98.26 92.76 1.008 0.02 96.95 97.27 0.836 0.78 1Standard Error of the Mean


105

Table 14. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on apparent total tract nutrient digestibility-Step 3 and 4, Finisher.

Step 3 Step 4 Finisher

Adaptation

Strategy SEM1 P -

Value Adaptation

Strategy SEM1 P -

Value Adaptation

Strategy SEM1 P -

Value Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton

Roughage Inclusion, % DM

15.00 15.00 7.50 7.50

Apparent Total Tract Nutrient Digestibility, % DM Basis

Dry Matter 71.56 67.79 3.410 0.48 65.36 67.52 3.054 0.64 70.65 76.17 1.653 0.06 Organic Matter 73.89 69.21 2.626 0.28 67.29 69.20 2.868 0.66 72.02 77.63 1.614 < 0.01 NDF 37.42 28.04 4.238 0.15 17.88 31.18 3.230 0.01 36.12 36.85 3.622 0.90 ADF 37.68 15.18 3.481 < 0.01 16.37 22.83 4.870 0.41 32.60 32.52 3.564 0.99 Hemicellulose 42.76 32.27 3.913 0.02 20.49 29.39 4.719 0.28 38.18 39.39 3.848 0.84 Crude Protein 69.60 66.52 2.201 0.20 61.78 62.73 3.671 0.86 62.59 71.76 3.176 0.19 Ether Extract 94.70 93.52 1.162 0.50 93.43 93.84 0.656 0.68 94.15 95.19 0.603 0.15 Starch 96.80 95.59 1.001 0.44 95.92 95.89 0.561 0.97 96.50 96.33 0.329 0.73 1Standard Error of the Mean


106

Table 15. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal dry matter degradability. In Situ DM Degradability, %

Time in Rumen (h)

SEM1

P -Value

Trt

P – Value Time

P – Value

Trt*time Variables Alfalfa Cotton 0 12 24 48 0 12 24 48 Wheat Hay 41.71 50.64 60.34 67.99 42.11 50.78 57.91 66.42 2.529 0.78 <0.01 0.82 Step 1 41.71 47.05 54.41 60.31 42.11 48.58 53.52 61.42 4.783 0.93 <0.01 0.98 Step 2 41.71 47.26 53.65 62.30 42.11 48.40 53.98 63.84 4.421 0.86 <0.01 1.00 Step 3 41.71 47.24 53.79 58.66 42.11 49.13 59.55 74.68 4.997 0.36 <0.01 0.13 Step 4 41.71 47.06 55.11 62.16 42.11 51.46 56.76 64.71 5.250 0.73 <0.01 0.95 Finisher 41.71 48.77 55.40 62.00 42.11 52.03 56.51 65.92 4.454 0.70 <0.01 0.92 1Standard Error of the Mean


107

Table 16. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal organic matter degradability. In Situ OM Degradability, %

Time in Rumen (h)

SEM1

P – Value trt

P – Value time

P – Value Trt*time

Variables Alfalfa Cotton 0 12 24 48 0 12 24 48 Wheat Hay 39.69 48.80 59.16 67.16 40.06 49.04 56.40 65.46 2.699 0.77 <0.01 0.81 Step 1 39.69 45.11 53.00 59.19 40.06 46.70 51.95 60.21 5.086 0.94 <0.01 0.98 Step 2 39.69 45.27 52.05 61.31 40.06 46.57 52.47 62.77 4.682 0.88 <0.01 0.99 Step 3 39.69 45.40 52.26 57.53 40.06 47.34 58.29 74.20 5.281 0.36 <0.01 0.15 Step 4 39.69 45.11 53.74 61.14 40.06 49.67 55.28 63.68 5.582 0.74 <0.01 0.95 Finisher 39.69 46.93 53.90 60.96 40.06 50.27 55.08 64.93 4.703 0.70 <0.01 0.93 1Standard Error of the Mean


108

Table 17. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal neutral detergent fiber degradability. In Situ NDF Degradability, %

Time in Rumen (h)

SEM1

P – Value

trt

P – Value time

P – Value

Trt*time Variables Alfalfa Cotton 0 12 24 48 0 12 24 48 Wheat Hay 20.17 35.54 44.93 56.17 19.97 35.93 40.20 53.27 5.017 0.75 <0.01 0.88 Step 1 20.17 31.50 37.10 45.60 19.97 32.44 33.88 45.50 8.032 0.95 <0.01 0.98 Step 2 20.17 32.17 39.59 48.92 19.97 33.22 35.33 49.92 7.861 0.95 <0.01 0.95 Step 3 20.17 31.49 39.87 44.03 19.97 33.96 42.65 65.32 8.481 0.54 <0.01 0.25 Step 4 20.17 26.14 41.44 48.66 19.97 36.10 43.88 51.24 9.120 0.73 <0.01 0.88 Finisher 20.17 28.11 41.99 48.29 19.97 36.62 43.06 52.83 7.701 0.71 <0.01 0.84 1Standard Error of the Mean


109

Table 18. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal acid detergent fiber degradability. In Situ ADF Degradability, %

Time in Rumen (h)

SEM1

P – Value

trt

P – Value time

P – Value

Trt*time Variables Alfalfa Cotton

0 12 24 48 0 12 24 48 Wheat Hay 11.25 32.83 40.17 51.47 12.27 31.17 34.25 49.15 8.252 0.81 <0.01 0.96 Step 1 11.25 24.60 30.88 40.11 12.27 27.02 24.44 40.51 11.894 0.96 <0.01 0.94 Step 2 11.25 30.42 37.25 43.93 12.27 29.90 25.92 45.94 11.552 0.88 <0.01 0.80 Step 3 11.25 27.99 37.80 38.41 12.27 32.77 32.28 62.93 11.879 0.67 <0.01 0.31 Step 4 11.25 16.68 38.96 44.14 12.27 33.27 37.97 46.95 12.563 0.75 <0.01 0.75 Finisher 11.25 19.96 39.92 43.70 12.27 34.36 34.23 49.03 11.587 0.78 <0.01 0.68 1Standard Error of the Mean


110

Table 19. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal hemicellulose degradability. Hemicellulose Degradability, %

Time in Rumen (h)

SEM1

P – Value

trt

P – Value time

P – Value

Trt*time Variables Alfalfa Cotton

0 12 24 48 0 12 24 48 Wheat Hay 30.44 38.65 50.41 61.57 28.83 42.33 47.04 58.00 3.325 0.66 <0.01 0.66 Step 1 30.44 47.56 44.26 51.93 28.83 41.24 49.13 51.26 7.377 0.87 0.03 0.90 Step 2 30.44 34.19 42.28 54.66 28.83 37.03 48.47 54.49 4.769 0.69 <0.01 0.81 Step 3 30.44 35.53 42.26 50.50 28.83 35.32 43.08 68.07 5.563 0.50 <0.01 0.17 Step 4 30.44 37.03 44.29 53.85 28.83 39.36 53.21 56.18 6.231 0.64 <0.01 0.80 Finisher 30.44 37.49 44.37 53.58 28.83 39.22 47.83 57.21 4.970 0.75 <0.01 0.90 1Standard Error of the Mean


111

Table 20. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on feeding behavior-Wheat Hay, Step 1 and 2. Wheat Hay Step 1 Step 2 Adaptation



P - Value


P - Value


30.00 30.00 22.50 22.50

Feeding behavior, min/d Eating 318 297 24.6 0.57 218 267 50.4 0.54 235 258 25.6 0.56 Drinking 2 5 2.4 0.37 10 25 6.8 0.19 20 13 4.3 0.33 Ruminating Up 152 167 23.4 0.67 55 31 13.7 0.30 43 5 3.7 < 0.01 Ruminating Down 387 373 41.4 0.83 445 375 28.9 0.16 452 490 25.3 0.34 Resting Up 147 177 39.1 0.62 153 123 22.1 0.39 132 113 26.4 0.65 Resting Down 390 347 29.8 0.36 492 491 64.6 1.00 480 417 22.4 0.12 Active 45 75 15.7 0.25 67 127 13.9 0.04 78 143 13.2 0.03 Total Resting 537 523 22.6 0.70 645 615 63.4 0.75 612 530 21.1 0.05 Total Ruminating 538 540 24.9 0.96 500 407 41.6 0.21 495 495 31.5 1.00 Chewing 857 837 17.4 0.46 750 641 51.6 0.25 731 753 28.2 0.63 Rumination/kg NDF consumed 346 378 49.5 0.67

236 210 29.2 0.58

290 257 29.5 0.50

Chewing/kg NDF Consumed 544 588 68.1 0.68

342 349 50.5 0.93

425 397 52.3 0.74

1Standard Error of the Mean


112

Table 21. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on feeding behavior-Step 3 and 4, Finisher. Step 3 Step 4 Finish Adaptation



P - Value


P -Value


15.00 15.00 7.50 7.50

Feeding Behavior, min/day Eating 243 232 17.3 0.66 170 195 17.4 0.37 167 168 31.9 0.97 Drinking 20 18 5.5 0.84 13 33 4.9 0.04 23 45 11.4 0.25 Ruminating Up 20 5 2.9 0.02 28 3 9.3 0.13 25 10 8.4 0.27 Ruminating Down 447 485 26.5 0.36

415 457 8.7 0.03

378 337 29.3 0.37

Resting Up 117 97 34.9 0.71 145 120 26.8 0.55 190 167 43.4 0.72 Resting Down 462 487 28.0 0.56 532 485 36.8 0.42 507 552 56.8 0.60 Active 132 117 24.9 0.69 137 147 18.3 0.71 150 162 26.5 0.77 Total Resting 578 583 43.8 0.94 677 605 21.6 0.08 697 718 30.6 0.64 Total Ruminating 466 491 22.5 0.50 443 460 7.0 0.19 404 346 32.5 0.30 Chewing 721 711 43.1 0.88 616 653 24.9 0.39 570 515 30.8 0.31 Rumination/kg NDF consumed 307 276 27.7 0.49

226 248 21.2 0.52

243 197 13.6 0.10

Chewing/kg NDF Consumed 461 410 48.4 0.52

312 354 34.4 0.45

329 301 17.8 0.34

1Standard Error of the Mean


113

Figure 3. The effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on average ruminal pH.

5

5.2

5.4

5.6

5.8

6

6.2

6.4

6.6

6.8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Wheat Hay Step 1 Step 2 Step 3 Step 4 Finisher

Ave

rage

Rum

inal

pH

Adaptation Steps (days)

Alfalfa Cotton

P = 0.11 P = 0.62 P < 0.01 P < 0.01 P = 0.98 P = 0.05


114

Figure 4. The effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on average ammonia concentration (mg/L).

0

5

10

15

20

25

30

35

0 4 8 16 0 4 8 16 0 4 8 16 0 4 8 16 0 4 8 16 0 4 8 16

Wheat Hay Step 1 Step 2 Step 3 Step 4 Finisher

Am

mon

ia C

once

ntra

tions

(mg/

L)

Adaptation Steps (hours post feeding)

Alfalfa Cotton

P=0.34P=0.02P=0.99 P<0.01 P=0.10P=0.21

ovinge lauren thesis - ttu-ir.tdl.org

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