Carbohydrates in Dairy
Nutrition
L.E. Chase and T.R. Overton
Dept. of Animal Science
Cornell University
Used with permission from Dairy Herd Management magazine
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
Feed
Additives
“Bypass”
Protein
Minerals and Vitamins
Rumen Degradable
NFC feeds
Protein
Grains Byproducts
Forages
Physical Fiber
Carbohydrates
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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
% of starch
(MCP per gram of OM)
100
90
80
70
60
50
40
30
20
10
0
100
86
88
Sucrose
Pectin
47
NDF
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?

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
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
100.0
Pre Bloom
EarlyBloom
MidBloom
FullBloom
95.0
90.0
Milk, lbs/day
85.0
80.0
75.0
70.0
65.0
60.0
55.0
50.0
20
30
40
50
60
% Hay
70
80
90
JDS: 66, Suppl. 1, 181
Alfalfa Maturity - Conclusions


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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?
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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
75
70
65
60
High dNDF
Low dNDF
lbs
55
50
45
40
DMI
Milk
4% FCM
Summary 

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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

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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?
40
35
30
25
lbs DM 20
15
40
50
60
10
5
0
0.85
0.95
F-NDF Intake, % of BW
1.05
What About NDF Digestibility?

Oba & Allen - 1999


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
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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
75
70
65
60
High dNDF
Low dNDF
lbs
55
50
45
40
DMI
Milk
4% FCM
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
90
Digestible NDF, %
80
70
60
50
40
30
20
25
30
35
40
45
NDF, %
50
55
60
NDF30 Distribution in Corn Silage by Chemistry, CVAS 2008
Mean = 60.0
SD = 6.9
N = 3830
50
60
70
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


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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)
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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 Particle
Separator
(moist, as-fed samples)
19, 8, 1.18 mm, pan; 40 horizontal shakes
On-Farm evaluation
Dry sieving Ro-Tap
(dried sample, standard
procedure for peNDF)
19, 13, 9.5, 6.7, 4.75, 3.35,
2.36, 1.18, 0.6 mm; shakes
for 10 min
Laboratory procedure
peNDF (dry sieving) and cow
response: chewing activity
r2=0.47
(Mertens, 1997)
peNDF and Ruminal pH
Positive Impacts of
Digestible NDF
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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)
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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
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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
Fastest
Slow e st
Source
Form
W heat
Steam flaked
B arle y
H ig h m oisture
O ats
D ry g round
C orn
D ry rolled
Sorg hum
D ry w ho le
Ruminal Feed Carbohydrate Fermentation Profile
•oat> wheat>barley> corn>milo
•grinding, ensiling, steam
•how fast and how much
Rate of Fermentation
sugars
Starches and pectin
starches
celluloses
EAT
1
3
5
7
9
11
13
15
Time after Feeding (h)
17
19
21
23
Rate of ruminal starch
digestion of corn
% digested
90
fine ground corn
80
cracked corn
60
40
20
0
2
12
hours after feeding
24
If there is too much nonfiber
carbohydrates or if it breaks down
too fast:
rumen pH
fiber digestion
Acidosis
Low milk fat
off-feed
Healthy rumen
performance
Summary

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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