Julie K. NorthcuttDepartment of Poultry Science

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0 6 12 180

100

200

300

400

500Age 45 Age 47

Length of Time off Feed (hours)

Vis

cera

Wei

ght (

gram

s)

Figure 1. Effects of length of feed withdrawal onbroiler viscera weight (Northcutt and Buhr, 1998).

water, 80 to 85 percent of the ingesta (partially di-gested food) within the broiler’s digestive tract willbeevacuated during the first 6 hours of feed withdrawal(Figure 1). However, when broilers are exposed todarkness, or after broilers are cooped, the evacuationrate is much slower. Research has shown that after a 2-hour feed withdrawal period, broilers in a dark envi-ronment had more feed in their crops than broilers inlighted environments (Table 1). After 4 hours of feedwithdrawal, lighting made no difference in the cropcontents, except when it was combined with cooping.Cooped broilers held in darkness for 2 hours had morethan twice as much feed in their crops than coopedbroilers held in the light. In addition, after 4 hours offeed withdrawal, there was twice as much feed with inthe crop of broilers held in darkness as compared tobroilers held in light. This information suggests that foroptimal feed passage, broilers should stay on litter 4hours or longer, and they should have adequate lightingup to the time of catching and during holding.

Temperature

Although variation in temperature of either thegrow-out house or the holding shed is known toinfluence the effectiveness of feed withdrawal, littleattention has been given to studying these factors. Ofthe information that has been published, most of thestudies have focused on feed withdrawal during hotweather. The list below summarizes some of thefindings.

1) Hot weather causes birds to be less active and toconsume less feed, but water consumption isgreater at higher temperatures. This can affect theconsistency of fecal material within the intestines.

2) In the evening and late afternoon after the sun goesdown and the temperature drops, birds may gorgethemselves. If feed is removed after the birds havegorged, a normal withdrawal period may not belong enough for adequate evacuation beforeprocessing.

3) As environmental temperatures approach 90degrees F and above, feed is retained for a longerperiod of time in the crop, gizzard and smallintestines of broilers.

4) In general, it is recommended that feed withdrawalprograms be extended 2 to 3 hours for broilersduring the summer months to accommodatechanges in the slower rate of feed passage.

Broilers grown during cold weather with housetemperature below 60 degrees F also retain feed intheir digestive tracts longer, and the birds are often toocold to get up and eat. As indicated by May and Lott(1992), “broilers are nibblers and eat regularly whenthe temperature is constant, and lighting is continu-ous.” When birds do not have normal eating patterns,

Table 1: Effects of lighting and cooping on the crop contents of 45-day old broilers

Weight of Crop Contents Following Feed Withdrawal

Holding conditions Lighting2 hours(grams)

4 hours(grams)

6 hours(grams)

8 hours(grams)

Litter Light 13.8bc 2.3b 0.6a 0.2a

Litter Dark 29.2a 4.0b 3.1a 0.5a

Cooped Light 11.8c 6.0b 0.4a 2.1a

Cooped Dark 21.0b 17.0a 3.5a 1.4a

May, J.D., B.D. Lott, and J.W. Deaton, 1990. Poultry Science 69:1681-1684.a-c Means within a feed withdrawal time with no common superscript are significantly different.

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0 6 10 12 14 18 240

75

150

225

300

375

Bilgili and Hess, 1997 Northcutt and Fletcher, 1998

Fo

rce

(gra

ms)

Length of Feed Withdrawal (hours)

Figure 2. Intestinal strength of broilers held with-out feed for various times before processing (Bil-gili and Hess, 1997; Northcutt and Fletcher, 1998unpublished).

Figure 3. Diagram of the digestive tract of a broiler (Parkhurst,C.R., and Mountney, G.J. 1987).

there is greater variability in the content and conditionof their digestive tracts. This can be detrimental for theprocessing plant in terms of carcass contamination.

Gastrointestinal (Digestive) TractAnd Fecal Contamination

Short Feed Withdrawal

When a complex designs a feed withdrawal pro-gram, they are deciding what they want in the bird’sintestinal tract when it enters the plant. Table 2 sum-marizes the condition and contents of broiler visceraafter various lengths of feed withdrawal (Northcutt etal., 1997). If the length of feed withdrawal is too short(less than 6 to 7 hours), the birds’ digestive tracts willbe full of feed at slaughter, and the intestines will belarge and rounded. For full fed birds, the feed filledlarge intestines take up a great deal of space in thebirds’ abdominal cavity, such that the duodenal loop ispositioned close to where the vents are opened. For thisreason, the filled intestines are easily cut during ventopening. In addition, processing broilers that are full offeed increases the likelihood that the force of eviscer-ation will cause intestinal material to leak out onto thecarcass.

Long Feed Withdrawal

If the length of feed withdrawal is too long (greaterthan 13 to 14 hours), the intestines will be weaker, andthe incidence of intestinal tearing during eviscerationmay increase. Figure 2 shows intestinal strength data ofbroilers after various feed withdrawal periods (Bilgili

and Hess, 1997; Northcutt and Fletcher, unpublished).Intestinal strength of broilers was approximately 10percent lower when the bird was held without feed for14 or more hours before processing.

In addition to weaker intestines, longer feed with-drawal times often result in bile contamination ofcarcasses because continuous bile is produced, and thegall bladder becomes enlarged. An enlarged gall blad-der may break more often during evisceration. Whenthe gall bladder reaches maximum capacity, excess bilebacks up into the liver and also releases into the duo-denum and gizzard with antiperistalsis (Figure 3). Thiscan alter the appearance of the liver and may alter theflavor of the liver. As a result of the bile, the gizzardlining will have a green appearance, indicating the feedwithdrawal may be excessive.

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After 4 hours of feed withdrawal, birds begin toconsume anything that is available, including litter andfecal material. Thus, there is a mixture of feed, litter,water and feces during the early withdrawal period.Because of the presence of the other material (residualfeed, water and litter), feces is not ease to identify inthe bird’s digestive tract until the bird has been withoutfeed for more than 14 hours (Table 2). Consumption offecal material should be avoided because it increasesthe potential for carcass contamination in the plant, andit may affect the plant’s ability to meet the USDAestablished microbiological standards for poultry.

Optimal Feed Withdrawal

With optimal feed withdrawal (empty digestivetract) before processing, the following advantages arerealized:

! Birds entering the plant carry less bacteria on theirfeet and in their feathers because less fecal materialis excreted in the coops during transportation andon the conveyor belts during unloading.

! Contamination of the scald water is reduced be-cause birds defecate less material during stunningand bleeding.

! Less fecal material in the bird’s digestive tractmeans less material is available for carcass con-tamination during evisceration.

! When carcass contamination is reduced, the pro-cessing lines run more efficiently, there is less car-cass trim (higher yields), lower water usage, andlower carcass E. coli counts.

In addition to reducing the amount of fecal materialthat is present in the birds’ digestive tracts at slaughter,feed withdrawal and water consumption by birds mayaffect the consistency of the fecal material. Table 3shows the relationship between feed withdrawal, fecal

consistency, and amount of fecal material (Wabeck,1972). As the length of time off feed increases, fecalmaterial may became more watery. In the plant, thismay translate into a higher percentage of carcasses thatare contaminated. When a carcass becomes contami-nated during processing, it is identified by the inspectoror a plant employee and removed from the mainprocessing line and placed on the salvage line forreprocessing. Each plant must used USDA approvedconditions to reprocess carcasses, including washingwith chlorinated water, trimming, or vacuuming. Fol-lowing reprocessing carcasses are re-inspected. If thecontamination is too great, a part (wing, drum, etc.) ofthe carcass or the whole carcass will be condemned(discarded as unfit for human consumption).

Table 3: Effect of feed withdrawal on consistencyand amount of broiler fecal material

Hour Condition Amount

0 Moist -

4 Moist 2.30

8 Firm 1.49

10 Firm 1.57

12 Loose 1.72

24 Watery 1.90

Wabeck, 1972.

Wesley (1972) found that plant carcass contami-nation was lowest (0.65 to 0.68%) for broilers pro-cessed after 8 to 12 hours of feed withdrawal, andhighest (2-6%) for broilers processed after 16 hours offeed withdrawal (Figure 4, page 5).

Table 2: Viscera contents after feed withdrawal.1

Time off feed(hours)

Cropcontents

Gizzardcontents

Intestinalshape

Sloughing ofintestinal mucus

Gizzard bile(percent)

0 - 3 Feed Watery feed Round No sloughing 0

9 Water Litter Flat Mild sloughing 30

12 Empty Litter Flat Sloughing 30

14 Empty Litter Flat and round Sloughing to heavy sloughing 35

16 - 19 Empty Litter and feces Flat and round Sloughing to heavy sloughing 40 to 70

1 Visual assessment of the intestinal contents. Intestinal shape indicates if the intestine is actively passing ingesta.

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2 4 6 8 10 12 14 16 18 20 240

1

2

3

4

5

6

7P

erce

nt C

arca

ss C

onta

min

atio

n

Length of Feed withdrawal (hours)Figure 4. Effects of Feed Withdrawal on CarcassContamination in the Plant (Wesley, 1972, reportedby Wabeck, 1992).

0 6 12 18 240

50

100

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25042 days 44 days 48 days

Length of Time off Feed (hours)

Wei

ght L

oss

(gra

ms)

Figure 5. Effects of Feed Withdrawal on LiveShrink in Male Broilers (Buhr et al., 1998).

Plant equipment and the USDA, Food Safety andInspection Service’s inspection system have changeddramatically since 1972 when Wesley conducted hisstudy on contamination. Most plants have a goal of 1percent reprocessing; however, even with as little as 1percent reprocessing, the plant loses a significantamount of yield. Using a conservative estimate, a plantmay lose between 5 and 7 percent carcass yield foreach bird that is reprocessed. Suppose an average-sizedplant (250,000 birds per day), processing 4 lb birds, hasto reprocess 1 percent of their carcasses. The followingcalculations can be made:

250,000 bird processed per dayx 1% Reprocessing 2500 birds hung back each day (salvage)

2500 birds reprocessed per dayx 4 lb live weight

10,000 lbs live weight

10,000 lbx 68% Carcass Yield (approximate

carcass yield as a percentageof the live weight)

6800 lbs carcass weight

6800 lbs carcass weightx 5% Yield loss

340 lbs yield

340 lbs lost product per day

Three hundred forty pounds of lost product may notseem like much, but the losses can add up consideringthat an average plant processes 260 days each year.

340 lbx 260 days

88,400 lbs lost product per year

Eighty-eight thousand, four hundred pounds of lostproduct per year occurs for 1 percent reprocessing;thus, if plants reprocessed 5 percent of their carcasses,they would lose close to 450,000 lbs each year. Thesecalculations demonstrate the need for plants to keepcarcass reprocessing as low as possible.

Carcass Yield and ContaminationLive Shrink

Live shrink refers to the weight lost by broilers dur-ing feed withdrawal. After broilers have been with-outfeed for more than 6 hours, they begin to draw mois-ture and nutrients from their own body tissues, and thisweight loss may then affect edible yield. The degree oflive shrink due to feed withdrawal is affected by birdage, sex, house temperature, eating patterns before feedwithdrawal, and preslaughter holding conditions (coop-ing time and holding temperature). Live shrink for amarket-aged broiler ranges from 0.2 to 0.3 percent ofthe bird’s weight before catching per hour of feedwithdrawal (Figure 5). The higher live shrink per hourof feed withdrawal occurs in male broilers. With liveshrink, a broiler held off feed for an extra 3 hoursbefore processing (e.g., 15 hours instead of 12 hours)will weigh approximately 0.03 lb less than a broilerprocessed 3 hours earlier. In an operation that pro-cesses 250,000 birds a day, the extra 3 hours of feedwithdrawal equates to reducing the live weight pro-cessed each week by 37,500 lbs. The majority of thegrowers in the United States are contract growers,which means that the company supplies the chicks,feed, litter, fuel and medication, while the grower sup-

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0 6 12 181500

1750

2000

2250

2500

2750

3000Live Wt Dry Carcass Chilled Carcass

Length of Time off Feed (hours)

Wei

ght (

gram

s)

Figure 6. Effects of Feed Withdrawal on LiveShrink, Dry Carcass Yield (before chilling), andChilled Carcass Yield in 45-Day Old Male Broilers(Northcutt and Buhr, unpublished data).

0 6 12 18 240

2

4

6

8

10Crop Ceca

Length of Feed Withdrawal (hours)

Log

bact

eria

/ gr

am

Figure 7. Enterobacteriacea counts for crop andceca of broilers held without feed for various timeperiods (Hinton et al., 1998).

plies the housing and labor for care of the birds. Grow-ers receive payment for a flock based on its weight atslaughter, which will be reduced if the birds are heldwithout feed for an excessive length of time (high liveshrink).

This does not mean that broilers given no feedwithdrawal will have the highest carcass yields. In fact,birds full of feed that weigh the same as birds held offfeed have lower carcass yields because their initialweight includes the digestive tract contents. Figure 6shows data for live weight, dry carcass weight, andchilled carcass weight for 45 day old male broilers.Carcass yield was highest for broilers on a 6 hour feedwithdrawal schedule. A 6-hour feed withdrawal pro-gram is impractical for industry because of carcasscontamination; however, these data demonstrate thatthe highest yield will be obtained by companies whostrike a balance between live shrink and carcasscontamination.

Carcass Contamination

Carcass contamination has become increasinglyimportant for the poultry industry because of theimplementation of the USDA’s Pathogen Reduction;Hazard Analysis and Critical Control Point System;Final Rule. One of the requirements of this rule is thezero tolerance of fecal material on carcasses enteringthe chiller. The ruling states that “visible fecal contam-ination is an important food safety standard becausefecal contamination is a major vehicle for spreadingdisease-causing microorganisms, such as Salmonella,to raw poultry.” Because of this ruling, companies areclosely monitoring carcass fecal contamination, andmany have lengthened their feed withdrawal programsbecause they feel that this will assist them in meeting

the zero tolerance policy. This bulletin has alreadydiscussed the detrimental conditions associated withexcessive feed withdrawal, and thus lengthening thewithdrawal period beyond the recommended lengthcreates more problems than it solves. Additionally,length of feed withdrawal affects the microbiologicalcondition of the broiler’s digestive tract, which may inturn affect the plant’s ability to meet the carcass micro-biological standards as stated in the final ruling. Hintonet al (1998) demonstrated that increasing the length oftime broilers were held without feed before processingcaused the pH of the ceca (pH 5.3 versus 6.5) to in-crease. At the higher pH, bacteria in the Enterobac-teriacea family, which includes Salmonella and E. coliamong others, multiply more readily. Figure 7 showsthe change in the bacteria populations of this family ofbacteria in the ceca and the crop. According to Hintonet al. (1998), increasing the length of feed withdrawalcauses a decrease in the lactic acid bacteria found inthe bird’s digestive tract, and with less lactic acidbacteria available to produce acid, the pH increases. Atthe higher pH, the environment is more favorable forgrowth of Enterobacteriacea bacteria. This researchdemonstrated that longer feed withdrawal time cancreate undesirable changes in the bacterial populationsof the digestive tract, and thus, excessive withdrawalperiods should be avoided.

RecommendationsBecause of the impact that feed withdrawal has on a

company’s bottom line profits, designing and imple-menting an effective program should be a team effortwith live production, and processing plant personnel.The following list contains factors to consider whenevaluating your feed withdrawal program:

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1) Keep accurate records of your actual feed with-drawal period (feeders empty to slaughter). Youmay not be operating on the schedule that youthink you are operating.

2) Monitor your flock for proper house temperature,litter moisture, and eating patterns. If the litter istoo wet, birds will find it difficult to get up andwalk to the feeders, and they will be more likely toremain in a sitting position in which case defecat-ing is difficult. You want to see birds moving aboutin the house, with no gorging patterns.

3) Try to avoid disturbing the flock immediately afterfeed withdrawal. This includes changing the light-ing, opening doors, etc., because any change willslows the evacuation of the digestive tract.

4) Keep the birds on litter with access to water aslong as possible to facilitate digestive tract empty-ing. Do not coop before 4 hours of withdrawal.

5) During hot weather, keep the birds as cool as pos-sible in the house and in the holding area.

6) Before the scheduled feed withdrawal time, do notallow birds to run out of feed; however, if you runout of feed (less than 0.5 lb of feed per feeder) atthe scheduled withdrawal time, leave the feedersdown until the catch crew arrives. By leaving thefeeders down during this early withdrawal period,birds are more likely to peak on the feeder thanthey are to peak at the litter. Since it is impossibleto consume litter without consuming feces, mini-mizing litter consumption is advantageous.

ReferencesBilgili, S. F. 1988. How effective is your feed with-

drawal program? Poultry Digest 47:132, 134.Bilgili, S. F., and J. B. Hess. 1997. Tensile strength of

broiler intestines as influenced by age and feedwithdrawal. J. Appl. Poultry Res. 6:279-283.

Buhr, R. J., J. K. Northcutt, C. E. Lyon, and G. N.Rowland. 1988. Influence of time off feed onbroiler viscera weight, diameter, and shear. PoultrySci. 77: (In Press).

Hinton, A., Jr., R. J. Buhr, and K. Ingram. 1998. Feedwithdrawal and carcass microbiological counts.Proceeding of the Georgia Poultry Conference,Athens, GA, September 30, 1998.

May, J. D., B. D. Lott, and J. W. Deaton. 1990. Theeffect of light and environmental temperature onbroiler digestive tract contents after feedwithdrawal. Poultry Sci. 69:1681-1684.

May, J. D., and B. D. Lott. 1992. Effect of periodicfeeding and photoperiod on anticipation of feedwithdrawal. Poultry Sci. 71:951-958.

Northcutt, J. K., and S. I. Savage. 1996. Preparing toprocess. Broiler Industry 59 (9):24-27.

Northcutt, J. K., S. I. Savage, and L. R. Vest. 1997.Relationship between feed withdrawal and visceracondition. Poultry Sci. 76:410-414.

Northcutt, J. K., and R. J. Buhr. 1997. Maintainingbroiler meat yields: Longer feed withdrawal can becostly. Broiler Industry 60 (12): 28-34.

Northcutt, J. K., and R. J. Buhr., 1998. Unpublisheddata.

Parkhurst, C. R., and Mountney, G. J. 1987. “Poultryand Meat Production,” Van Nostrand ReinholdCompany, New York, N.Y.

Wabeck, C. J. 1972. Feed and water withdrawal timerelationship to processing yield and potential fecalcontamination of broilers. Poultry Sci. 51:1119-1121.

Wabeck, C. J. 1992. Update: Feed withdrawalguidelines. Broiler Industry 55 (1):64-67.

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Bulletin 1187 Reviewed January, 2010