Carbohydrates in Dairy Nutrition

Carbohydrates in Dairy Nutrition

L.E. Chase and T.R. OvertonDept. of Animal Science

Cornell University

Used with permission from Dairy Herd Management magazine

ForagesPhysical Fiber

Rumen DegradableProtein

NFC feedsGrains Byproducts

Minerals and Vitamins

“Bypass”Protein

FatSuppl.

FeedAdditives

The Feed Pyramid (Rick Lundquist, 1995)

Use the Feed Pyramid to think about how rations should be formulated and cows fed. A basic ration with high quality forages (bottom three sections of pyramid) should support up to 75 lbs (or more) of milk per day. Fats, bypass proteins and feed additives are needed by higher producing cows and should top off the base ration

Carbohydrates

Comprise 65 - 75% of the total dry matter consumed by the cow

Most important source of energy for rumen bugs

Carbohydrates are essential in maximizing microbial protein

Provide the major component of NE-l

Maximum Microbial CP Yield(MCP per gram of OM)

47

86 88100

0102030405060708090

100

% o

f sta

rch

NDF Sucrose Pectin Starch

(Hall and Herejk, 2001)

What Does Your Forage Customer Want?

What Does Your Forage Customer Want? A consistent supply of

- High quality- High digestibility- “Effective” physical fiber- Palatable- Well-fermented silage

How Important is Forage Quality? Kawas et. al., Univ. of Wisconsin Used alfalfa hay 4 stages of maturity 4 levels of grain feeding Short-term trial

Milk Production as Affected by Hay Quality

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

90.0

95.0

100.0

20 30 40 50 60 70 80 90

% Hay

Milk

, lbs

/day

Pre BloomEarlyBloomMidBloomFullBloom

JDS: 66, Suppl. 1, 181

Alfalfa Maturity - Conclusions Feeding increased grain could not

overcome the effects of lower forage quality

Milk decreased about 1 lb./day for each day increase in maturity after prebloom

Milk decreased by 1 lb./day for each 1% increase in alfalfa NDF content

How Important is Forage Digestibility?

Data from 23 research trials Alfalfa hay, alfalfa silage, corn silage,

timothy silage, wheat silage Reported NDF dig. (in situ or in vitro) High NDF dig. = 62.9% Low NDF dig. = 54.5%

Oba & Allen – Michigan State - 1999

DMI & Milk Production

40

45

50

55

60

65

70

75

DMI Milk 4% FCM

lbsHigh dNDFLow dNDF

Summary - 1 unit of increased NDF digestibility ( i.e. 45

to 46%)= + 0.37 lbs. DMI + 0.51 lbs. milk + 0.55 lbs. 4% FCM This may not be a linear response across all

levels of NDF digestibility

Using NDF to Determine Forage in the Ration NDF is currently the best method to use to

set the quantity of forage to be fed. Guideline is between 0.85 and 1.1% of

body weight as forage NDF (F-NDF)

Example

1400 lb. cow 0.85% BW = 11.9 lbs. of F-NDF 1.1% BW = 15.4 lbs. of F-NDF

Typically, I use about 1% of BW as a starting point

How Many lbs. of Forage DM to Feed?

05

10152025303540

lbs DM

0.85 0.95 1.05F-NDF Intake, % of BW

405060

What About NDF Digestibility?

Oba & Allen - 1999

Data from 23 research trials Alfalfa hay, alfalfa silage, corn silage, timothy

silage, wheat silage Reported NDF dig. (in situ or in vitro) High NDF dig. = 62.9% Low NDF dig. = 54.5%

DMI & Milk Production

40

45

50

55

60

65

70

75

DMI Milk 4% FCM

lbs High dNDFLow dNDF

Summary -

1 unit of increased NDF digestibility ( I.e. 45 to 46%)=

+ 0.37 lbs. DMI + 0.51 lbs. milk + 0.55 lbs. 4% FCM This may not be a linear response across all

levels of NDF digestibility

The relationship between corn silage NDF and digestible NDF

20

30

40

50

60

70

80

90

25 30 35 40 45 50 55 60NDF, %

Dig

estib

le N

DF,

%

50 60 70

NDF30 Chem

DistributionsNDF30 Distribution in Corn Silage by Chemistry, CVAS 2008

Mean = 60.0SD = 6.9N = 3830

Physically effective NDF

peNDF Related to physical properties of NDF that

stimulate chewing and establish rumen digesta mat Animal response = chewing activity

peNDF and Chewing Activity (cont.) Cows only chew ~10-11 h/d (Welch, 1982) 88 min to chew 1 lb of NDF from oat straw

Or, 1.5 h Only takes 6.8 lb straw NDF to reach cow’s

capacity (or, 8 lb of straw DM)! Explains response to 1 lb supplementation (or to

bedding)

Importance of NDF and Chewing Activity Chewing data set (Mertens, 1997)

Equivalent particle length Alfalfa, coarse 60 min/lb of NDF Bermudagrass 68 min/lb Ryegrass 63 min/lb Oat straw 88 min/lb Corn silage 44 min/lb

Two Basic Methods for Measuring Physical Fiber (Particle Size)

Penn State ParticleSeparator(moist, as-fed samples)19, 8, 1.18 mm, pan; 40 horizontal shakesOn-Farm evaluation

Dry sieving Ro-Tap(dried sample, standardprocedure for peNDF)19, 13, 9.5, 6.7, 4.75, 3.35, 2.36, 1.18, 0.6 mm; shakes for 10 minLaboratory procedure

peNDF (dry sieving) and cow response: chewing activity

(Mertens, 1997)

r2=0.47

peNDF and Ruminal pH

Positive Impacts of Digestible NDF Increased DMI Increased Energy Intake Higher ruminal pH Increased A:P No lactic acid Greater MCP production Less need for RUP supplements More constant supply of absorbed nutrients

NFC (Non-Fiber Carbohydrates) 4 basic categories Organic acids (no energy for bugs) Sugars Starch Neutral-detergent soluble fiber (pectin's,

beta-glucans, fructans, etc.) Is a calculated value

Nonfiber Carbohydrates

All NFC are NOT created equal! Chemically & nutritionally diverse Different effects on cow health and performance

NFC = 100 – (NDF+CP+EE+Ash) NFC = 100 – ((NDF-NDICP)

+CP+EE+Ash) NSC = sugars + starch

directly measured

General recommendation for NFC 37 to 42% of DM

Rumen Degradability of CHO Sources

Source FormFastest Wheat Steam flaked

Barley High moistureOats Dry groundCorn Dry rolled

Slowest Sorghum Dry whole

Ruminal Feed Carbohydrate Fermentation Profile

EAT 1 3 5 7 9 11 13 15 17 19 21 23Time after Feeding (h)

Rat

e of

Fer

men

tatio

n

sugars

Starches and pectin

starchescelluloses

• oat> wheat>barley> corn>milo• grinding, ensiling, steam• how fast and how much

Rate of ruminal starch digestion of corn

fine ground corn

cracked corn

hours after feeding2 12 24

%

dige

sted

90

80

60

40

20

0

rumen pH fiber digestion

AcidosisLow milk fatoff-feed Healthy rumen

performance

If there is too much nonfiber carbohydrates or if it breaks down

too fast:

Summary

Carbohydrates are the key to providing energy for both microbial bug growth and energy for the cow

Structural (fiber) carbohydrates stimulate chewing and rumination

Non-structural (sugars, starch) provide rapidly available energy in the rumen but can also lower rumen pH