OHIO AGRICULTURAL RESEARCH AND DEVELOPMENT CENTER

Bill Weiss

Department of Animal Sciences

Wooster, 44691

Importance of Starch to the Energy Supply of Dairy Cows

Starch: do cows need it?

1. Most forages (‘the natural food’ for ruminants) have <5% starch

2. Of the 68 major feeds listed in NRC, only 13 have > 20% starch

3. Many beef cows live to a ripe old age and never eat a gram of starch

Energy Sources (% of DE) Typical US Dairy Diet

20%

7%

24%

34%

4%

11%

Protein Fat Fiber Starch Sugar Other

*Starch rarely <25%

If you are going to formulate for starch you must get feeds assayed

Owens, 2009 Tri-State Dairy Nutr. Conf. Proc.

Starch

Cheap Energy More Bacterial Protein

Less Manure

It is a good thing

Starch increases bacterial protein

synthesis (usually)

0

50

100

150

200

250

g M

icro

bia

l p

rote

in

Glucose Starch NDF

0

50

100

150

200

250

300

350

400

450

31% Starch 21% Starch

Hristov et al., 2005 Oba and Allen, 2003

GE

DE

ME

NEL

Fecal Energy

Heat increment

Urine/methane

Energy

Retained + work

+ maintenance

Energy Flow

Average Energy Values (Beltsville Energy Lab)

4,60 3.06 2,64 1,63

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

Mc

al/

kg

DM

67% 57% 35%

87% 53%

62%

N = 301 GE DE ME NEL

8% M

5%U

Energy from Carbohydrates Diet DMI = 23 kg lbs 25% starch 5.8 kg 5.3 kg dStarch 32% NDF 7.4 kg 3.5 kg dNDF

Starch 22 Mcal DE 12.8 Mcal NEL NDF 15 Mcal DE 7.4 Mcal NEL

0.78 X

1.5 X 1.7 X

On average 1 kg of starch = 2.3X

more NEL than 1 kg NDF

1.5 X

Starch and Energy Supply

Function of:

1. Starch digestibility

2. Starch concentration

NEL

Su

pp

ly, M

cal/

day

Digestibility or Concentration

Non-linear relationship

Optimal Dietary Starch %

Usually 20 to 30%

Too Low

Low intake Inadequate energy

Too High

Low intake Low fiber digest Acidosis

1. Economics (feed costs)

2. Cow requirements

3. Available feeds

Starch (corn) Digestibility in Lactating Dairy Cows

13 experiments 58 diets 287 observations Avg = 92.1%

16 experiments 65 diets 356 observations Avg = 48.5%

Grass-based

NDF (corn silage, alfalfa, NFFS) digestibility by lactating dairy cows

What affects starch digestibility?

1. Plant species •Wheat = barley = oats > corn > sorghum

2. Plant (seed) maturity •Immature > mature

3. Maize hybrid (type) •Dent > flint

4. Processing •Fine > coarse •Steam-flake > dry roll

Grain Processing and Starch Digestibility

30

40

50

60

70

80

90

100

Corn Sorghum Barley

Sta

rch

Dig

es

tib

ilit

y,

%

Cracked

Ground

Fine grind

Steam flaked

HM, rolled

HM, ground

Literature review, Firkins et al., 2001

Particle size of dry corn

50

60

70

80

90

100

Sta

rch

dig

esti

bil

ity, %

<1 1 to 1.5 1.5 to 2

3 to 3.5 3.5 to 4

1,3

1,32

1,34

1,36

1,38

1,4

1,42

1,44

1,46

0 1 2 3 4F

CM

/DM

I

Mean Particle Size, mm

TMR: 2.8%/mm

Ferraretto et al., 2013

Grind corn to <1000 μm

Vitreous or flinty

Pictures courtesy of Mike Allen, MSU

Floury

Hybrid Effects: Vitreousness

Dent

Vitreousness of DRY Corn

• Diets balanced for starch and starch source

• ~53% of starch from corn grain

• Hybrid 1: 3% Vitr

• Hybrid 2: 67% Vitr 20

30

40

50

60

70

80

90

100

Total Ruminal

'Soft'

'Hard'

~5%

Taylor and Allen, 2005

Kernel Texture

Very soft Very hard

Floury Flinty Dent

Real world range in hardness will be less

and

so will range in starch digestibility

Be patient: Starch digestibility of HM corn and corn silage

increases over time

0

10

20

30

40

50

60

70

3 h

Sta

rch

Dig

est,

%

2 month

4 mo

6 mo

8 mo

10 mo

DM ~36%

Newbold et al., 2006

Reduce diet % starch as corn silage and HM

corn ages

Young vs old corn silage

1 to 1.5 % units of starch

Is variation in starch digestibility important?

2,5

2,6

2,7

2,8

2,9

3

3,1

3,2

3,3

3,4

3,5

20% Diet Starch 30% Diet Starch

DE,

Mca

l/kg

0.88 Digest

0.98 Digest

+3% +4%

~ 3 kg milk ~2 kg milk

Maximize Starch Digestibility

0

5

10

15

20

25

30

24%Starch

26%Starch

28%Starch

% D

igesti

ble

Sta

rch

88% 96%

Starch digestibility Starch Digestibility

(dairy)

80 – 99% (88-96%)

8% Digest =

2% Concentration

Cost to digest vs cost of starch

Fecal starch % predicts starch digestibility (Fecal starch also predicted by NIRS)

Fredin et al. (2014; JDS 97:1862)

Wisconsin Dairy Survey (30 farms) (Huibregtse et al., 2012)

75% had <5% starch

Why does this occur?

Starch and Energy Supply N

EL S

up

ply

, Mca

l/d

ay

Digestibility or Concentration

1. Negative effects on intake

2. Negative effect on fiber digestibility

• Wheat vs. corn

– 19% fNDF

– 36% Starch (Lechartier and Peyraud, 2010)

• Dry vs. High

moisture corn

– 16 or 25% fNDF

– 31 or 21% starch (Oba and Allen, 2003)

14

16

18

20

22

24

DM

I, k

g/d

Wheat Dry corn HM corn

Diets with excess FERMENTABLE starch can reduce DMI

Grain

Source

Corn grain

storage

High Low

starch

On average, a 5%unit increase in starch = ~2.5%unit decrease in NDF digestibility

(Meta-analysis; Ferraretto et al., 2013)

Y = 58.3 – 0.48X

320 Trt means

Associative Effects: Steam-flaked corn density

0

10

20

30

40

50

60

70

80

90

100

R. Starch TT Starch TT ADF TT OM

0.39

0.32

0.26 kg/L

Firkins et al., 2001 from Plascencia and Zinn, 1996

Alfalfa hay + ~24% Starch

% of NDF from Wheat

0 13% % of ADF from Wheat

0 6%

Leddin et al., 2009

52 32% NDF

29 17% ADF

Confounding is Inevitable

2 20% Starch

Changing starch% while maintaining ‘inherent’ NDF digestibility

NDF:Starch

0.75 1.0 1.25

Corn silage 42 42 42

Corn grain 34.8 29.0 23.3

SH + CSH 0 5.6 11.3

NDF 24.7 28.6 32.2

Starch 33.3 30.1 25.4

IS NDF digest, % 43 43 43

NDF digest, % 45.3 46.4 46.4

Beckman and Weiss, 2005

Starch Depression of NDF Digestibility: Mechanisms

1. rumen pH alters bacterial population

2. pH-(in)dependent slowing of bacterial attachment

3. pH-(in)dependent inhibition of cellulolytic enzymes

4. rumen pH reduces bacterial population

Fermentable Starch Rate of NDF Digest

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

21% Starch 31% Starch

%/h

r (p

dN

DF)

Dry Corn HM Corn

Oba and Allen, 2003

- In vivo (lact cows)

- Corn replaced corn and alfalfa silage

- Diets had ~5% DDG

- DMI: High>Low

Starch and Depressed Fiber Digestion: More than just pH

10

20

30

40

50

60

70

5,5 6,2 6,8

ND

F, IV

PED

,%

Media pH

None-Alf Corn-Alf

Grant 1994

1. Diets: 0 or 29% starch

2. pH was fixed

3. Low pH, starch was –

4. High pH, starch was +

Amylase may stimulate NDF digestion

20

30

40

50

60

70

80

90

100

Starch NDF . Starch NDF

-Amylase +Amylase

1. Amylase often does not increase starch digest

2. Amylase often increases NDF digest

Rumen Total

Noziere et al., 2014 Weiss et al., 2011

Cow Energetics:

or

How much should nutritional models discount NEL as starch

increases ?

Is the decrease in NDF digestibility important?

Assumptions:

▪ DE from NDF and starch = 4.2 Mcal/kg (from NRC)

▪ Starch digest: 92% (from Weiss dataset)

▪ NDF digest: 48%

▪ Effect of starch on NDF digest = -0.48/% (from Ferraretto et al., 2013)

5% Substitution of Starch for NDF: Effects on DE

DE increases 3.11 to 3.20 Mcal/kg +2.9%

5% Substitution of Starch for NDF: Effects on ME

Assumptions:

▪ Methane from digestible starch and NDF (modified from Jentsch et al., 2007)

▪ NDF digestion assumed to decrease

▪ No effect on urinary N

Basal CH4 from CHO: 0.16 Mcal/kg +5% starch, -5%NDF: 0.155 Mcal/kg

-3.1%

%5 Substitution of Starch for NDF: Effects on ME to NE

Assumptions:

▪ Propionate 2 units, acetate 2 units (Weiss et al., 1991)

▪ Propionate to glucose k = 0.59 Acetate to fat k = 0.29 (from Hanigan, 2012 and Baldwin, 1995)

Basal k = 0.275 +5% starch, -5%NDF k = 0.282

+2.5%

5% Substitution of Starch with NDF: Effect on NEL

Assumed decrease of 0.025 in NDF digestibility

Basal +5%Starch

DE, Mcal/kg 3.11 3.20

ME, Mcal/kg 2.69 2.79

NEL, Mcal/kg 1.70 1.79

+2.9%

+3.7%

+5.3%

+6.5% No Effect on NDF

Potential Factors Affecting Starch Affect on NDF Digestibility

1. Starch fermentability

2. Source of NDF

- Species (corn silage, alfalfa, grass, NFFS)

- ‘Inherent’ NDF digestibility (forage maturity, soyhulls vs wheat bran, etc)

3. DMI interactions

Starch Fermentability and NDF Digest

10

15

20

25

30

35

40

45

50

55Less More

Forage based diets, mostly alfalfa+corn silage

Treatments were:

Wheat or barley vs corn

HM vs dry corn

SF-corn vs dry corn

Degree of vitreous

Fine vs coarse ground corn

For modeling: How do you measure fermentability?

Type of forage and Starch Effect

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

ND

F D

ige

stib

ility

Estimated Starch, %

Alf OG

40

44

48

52

56

60

20 25 30 35

ND

F D

ige

stib

ility

, %

Diet Starch, %

75:25 AS:CS

25:75 AS:CS

Weiss and Shockey, 1991

No interaction No interaction

Weiss et al., 2009

Starch and Byproduct NDF

Decrease starch by increasing nfNDF NDF digestibility ◦nfNDF can be highly digestible ◦ reduces (-)associative effect

Decrease starch by reducing fNDF NDF digestibility ◦does faster ROP counter reduced negative associative effect

Highly dependent on byproduct

Conclusions

1. On average, starch NDF digestibility

2. On average, starch NEL

3. Usually, starch ferment NDF digest

4. Source of fiber affects response

5. DMI affects response

6. Energy modeling must include more than just starch%

http://dairy.osu.edu