Group Title: Circular
Title: Nonstructural and structural carbohydrates in dairy cattle rations
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Title: Nonstructural and structural carbohydrates in dairy cattle rations
Series Title: Circular
Physical Description: 5 p. : ; 28 cm.
Language: English
Creator: Harris, Barney
Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1993
Subject: Dairy cattle -- Feeding and feeds   ( lcsh )
Milk yield   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (p. 4).
Statement of Responsibility: Barney Harris, Jr.
General Note: Caption title.
General Note: "November 1993."
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Bibliographic ID: UF00008566
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6830
ltuf - AJW3593
oclc - 29579719
alephbibnum - 001888414

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Florida Cooperative Extension Service

Circular 1122
November 1993

*-*-* r 71.-f-*

Nonstructural and Structural Carbohydrates in Dairy Cattle
Barney Harris, Jr.2


Carbohydrates are the largest component in the
dairy ration and contribute 60 to 70% of the net
energy used for milk production. Carbohydrates may
be divided into fiber and non-fiber components. The
fiber or structural portion, commonly called neutral
detergent fiber (NDF), includes cellulose, lignin, and
hemicellulose (Table 1). The NDF fraction
represents the slower digestible fibrous portion of the
ration. The nonstructural or non-fiber carbohydrates
(NFC) include starch, sugars and pectin.

Microorganisms ferment carbohydrates to volatile
fatty acids (VFAs) in the rumen, where they are
absorbed and utilized as energy sources for
maintenance, synthesis of milk, and tissues. Also, the
VFAs (acetic, propionic, and butyric) provide carbon
units for synthesizing milk components such as milk
fat. Glucose is needed by the mammary gland to
synthesize lactose. The liver synthesizes glucose from
propionic acid for use in other body tissues. Acetic
acid is needed for about 50% of the milk fat produced
in the mammary gland. The amount and ratio of
volatile fatty acids (VFAs) produced in the rumen
may alter milk composition. As an example, rapidly
fermenting carbohydrates favor the production of
propionic acid; slowly degrading fibrous or structural
carbohydrates promote acetic acid production.

Rations low in fiber may result in too little acetic
acid being produced in the rumen, resulting in
possible acidosis and reduced milk fat production.
Adequate amounts of effective fiber are needed in the
ration for the maintenance of health.

The key to good, nutritionally-balanced and
efficiently-utilized rations is to formulate diets with an
optimum amount of both structural and nonstructural
carbohydrates that maximize production performance.
Aldrich et al. (1993) reported that diets containing
36% NSC resulted in the highest passage of bacterial
nitrogen to the small intestine. Hoover et al. (1991)
concluded from continuous culture studies that diets
with an NSC level of about 37% of DM provided
sufficient energy for optimum microbial growth.
MacGregor et al. (1983) conducted a study where
cows were fed low (24.9%) or high (32.9%) starch-
containing diets. Cows fed high-starch diets increased
in milk production (P<.07) and DMI (P<.08)
compared to those fed the low-starch diet. Nocek
(1993) concluded from his studies that appropriate
nitrogen or protein fractions must be-provided with
these various carbohydrate fractions in order for
optimal microbial synthesis and carbohydrate
utilization to occur.

1. This document is Circular 1122, Dairy Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences,
University of Florida. Publication date: November 1993.
2. Professor, Dairy Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida,
Gainesville FL 32611.
The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research,
educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap,
or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office.
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Dean

U^IWCIr.-t'TT OF F'!rP T'% I I7IES

Nonstructural and Structural Carbohydrates in Dairy Cattle Rations

Table 1. Carbohydrate fraction of the ration divided into two
categories structural and nonstructural.

Structural Nonstructural
(fiber) (non-fiber)
cellulose starches
hemicellulose sugars
lignin pectin

Nonstructural carbohydrates (NSC) represent the
more rapidly digested fractions in the rumen. In
plants, they are located mostly in the seeds. While
different equations have been developed for
calculating NSC, in this paper the following equation
is used where NDF = neutral detergent fiber.

NSC = 100-(NDF + Crude protein + Fat + Ash)

The fibrous carbohydrates represent the portion
of the ration that is more slowly digested. The
fibrous carbohydrates occupy more space in the gut
and require extensive chewing to reduce the particle
size for passage to the lower digestive tract.

The fiber in a ration is analyzed by laboratory
procedures for either crude fiber, acid detergent fiber
(ADF) or neutral detergent fiber. The NDF
procedure measures all the cellulose, hemicellulose
and lignin. Crude fiber measures only cellulose and
some lignin; ADF measures cellulose and all the
lignin. For this reason, ADF appears to be more
closely associated with digestibility and NDF to rumen
fill or dry matter intake. Since dry matter intake and
milk production correlate closely, any component of
the ration affecting dry matter intake would affect
milk production. Suggested fiber content of rations
for high- producing cows is in Table 2.

An experiment was conducted by Staples et al.
(1992) to evaluate the value of NDF concentration in
diets in order to formulate the desired forage-to-
concentrate ratio. Forages selected for the study
included corn silage, elephantgrass silage, bermuda-
silage, and sorghum silage. The forages were adjusted
in the diets to give NDF values of 31, 35 and 39
percent. The results are in Table 3.

Milk production averaged nearly 50 lb/day over
the 84-day experiment. All silages, except for

Table 2. Fiber guidelines for formulating diets for lactating
dairy cows.

Fiber Analysis Minimum Recommended
Crude fiber 15-17 15-21
Acid detergent fiber 19-21 19-24
Neutral detergent fiber 25-28 25-352

Forage Program % of DM
Corn silage (CS) (only forage) 45-55
CS + 10 Ibs alfalfa hay 35-40
Bermuda haylage (35-40% DM) 20-30
CS + 7 Ibs cottonseed hulls 35-40
CS + 5 Ibs CSH + 5 Ibs alf hay 32-40
CS + 7 Ibs bermuda hay 32-40
CS + 20-25% high fibrous by-products 40-45

Nonstructural carbohydrates (NSC)
Minimum 25-33
Optimum 34-38
Maximum 39-45
1National Research Council, 1989.
2Range varies with forage type and use of by-products.

sorghum silage, supported similar amounts of milk
production. Cows consuming sorghum-based diets
produced about 3.3 lb/day less milk than cows on
other diets. Similar amounts of milk were produced
on 31% and 35% NDF rations, but production
decreased when cows received diets containing 39%

Corn and alfalfa silage were used in a study by
Purdue University workers to measure the
performance of early lactation cows fed TMRs
formulated to differ in NDF content by varying the
amount of forage (silage) in the ration. The forage
source used was a 50:50 mixture of corn and alfalfa
silage at 41.2, 55.3 and 69.5% (DM) of diets
containing 26, 31 and 36% NDF. The results are in
Table 4.

Page 2

Nonstructural and Structural Carbohydrates in Dairy Cattle Rations

Table 3. Dry matter intake, mild yield, milk composition and FCM production of lactating cows fed four
silage-based diets.

NDF DM11 MY2 FCM3 Fat4 Protein5
Diets (%) -(Ib/d)-- (%)-
Corn silage 31 43.8 51.6 46.8 3.39 3.20
35 43.0 51.6 46.3 3.38 3.10
39 41.2 50.3 46.5 3.51 3.10

Elephantgrass 31 46.1 51.6 46.2 3.32 3.12
silage 35 45.1 51.3 46.0 3.33 3.08
39 42.0 47.8 42.7 3.31 3.06

Bermudagrass 31 43.5 51.1 44.9 3.26 3.20
silage 35 41.4 51.0 45.8 3.35 3.04
39 40.7 46.8 41.7 3.27 3.09

Sorghum 31 44.5 48.6 43.9 3.38 3.18
silage 35 41.4 46.2 41.5 3.32 3.10
39 39.0 46.3 41.5 3.31 3.07

1DM intake = decrease due to NDF, P = 0.16.
2FCM yield = decrease due to % NDF, P = .005.
3Milk yield = decrease due to % NDF, P = .001.
percent milk fat = CS > elephantgrass, P = .003.
5Milk protein = increase due to % NDF, P = .003.
Staples at al. (1992), Proc. Fl. Dairy Prod. Conf.

Table 4. Adjusted means for dry matter intake, milk yield, milk composition and FCM1.

Total Mixed
Item 26 31 36 SE Level of sig.

DM intake, Ib/d 49.4 48.2 44.2 .06 .001
Milk yield, Ib/d 74.6 76.1 70.2 .54 .001
FCM, Ib/d 70.0 69.1 66.4 .40 .034
Milk fat, % 3.52 3.46 3.60 .08 .464
Milk protein, % 2.99 2.92 2.86 .04 .133
1Colenbrander et al. (1988). Dairy Day, Purdue Univ.
sig. = significance; SE = standard error.

Page 3

Nonstructural and Structural Carbohydrates in Dairy Cattle Rations

The results in Table 4 show a significant
difference in DM intake, milk yield and fat-corrected
milk (FCM) between the two lower NDF values and
36% NDF. This is in contrast with studies by Staples
et al. (1992) where 35% NDF diets performed equally
as well as 31% NDF diets except in the sorghum
silage diets. The differences are probably due to
forage type since forages vary considerably in NDF
content. In most forage type rations, NDF values
from 31% to 36% appear to be acceptable for high
producing cows. In contrast, lactating cows appear to
perform better on lower NDF rations when alfalfa hay
and similar legumes are the major forage types.

Formulating rations based on NDFvalues requires
a good understanding of forage types and by-product
feedstuffs. To effectively use NDF values in
formulating rations containing large amounts of by-
products, discount values (Mertens, 1992) should be
applied to certain by-product feedstuffs such as
distillers' grains, hominy feed and soybean hulls. The
reason is because the values given in the NRC
publication on nutrient requirements of dairy cattle
(1989) are higher for these feedstuffs than for alfalfa

The physical form of a feed has a great impact on
the effectiveness of the fiber in the diet. Chewing
time is a good indication of that effectiveness for
certain feedstuffs. For example, Sudweeks et al.
(1981) showed that long alfalfa hay containing 40%
acid detergent fiber (ADF) was chewed at the rate of
28.2 min/lb of DM; ground and pelleted alfalfa hay
was chewed at the rate of 16.8 min/lb of DM. This
demonstrated that long alfalfa hay was a more
effective source of fiber than pelleted alfalfa. In
contrast, both citrus pulp and cottonseed hulls
stimulated chewing time at 14 min/lb of DM which
indicated they had equal effective fiber values. In
reality, citrus pulp is low in effective fiber (12%) and
cottonseed hulls are high in effective fiber (43%).

By-product feedstuffs are used extensively in dairy
cattle diets throughout the country. Frequently, these
by-product feedstuffs are used as major sources of
fiber or as fiber extenders in dairy cattle diets. While
performance may remain good, the NDF content of
the diet is sometimes higher than suggested in the
1989 NRC publication for high-producing cows.
Attempting to lower the NDF content in the diet
results in milk fat depressions, looseness in bowel and
acidosis type conditions. The problem can frequently
be avoided by adjusting or discounting the NDF
content of the by-product feedstuffs being used in the

diets. Table 5 contains a list of selected feedstuffs
with NRC values taken from the 1989 NRC
publication, discount values (DV), and adjusted NDF
(ANDF) values. Similar adjusted NDF values have
been suggested and developed by Mertens (1992).

The key to a successful feeding program for high-
producing dairy cows is a balance between the needs
for ruminally available protein and carbohydrates that
will optimize microbial growth and metabolism in the
rumen. As these needs are met, fine-tuning the
ration with sources of bypass protein and fats may be
advantageous. While the level of NSC needed in the
ration will vary with forage type and use of by-
products feedstuffs, a suggested range is 35% to 45%
NSC. The lower range is recommended when rations
contain good quality hay and/or silage with natural
grains such as corn and limited amounts of
ingredients such as citrus pulp and soybean hulls.
Using adjusted NDF and NSC values for by-product
feedstuffs will help minimize the formulating
problems encountered when attempting to use higher
levels of by-product feedstuffs in the diet.


Aldrich, J. M., L. D. Muller, G. A. Varga, and L. C.
Griel, Jr. 1993. Nonstructural carbohydrate and
protein effects on rumen fermentation, nutrient
flow, and performance of dairy cows. J. Dairy Sci.

Hoover, W. H. and T. K. Miller. 1991. Balancing
dairy rations for proteins and carbohydrates.
Calif. Animal Nutr. Conf.

MacGregor, C. A., M. R. Stokes, W. H. Hoover, H.
A. Leonard, L. L. Junkins, Jr. C. J. Sniffen and R.
W. Mailman. 1983. Effect of dietary
concentration of total nonstructural carbohydrates
on energy and nitrogen metabolism and milk
production of dairy cows. J. Dairy Sci. 66:39.

Mertens, D. R. 1992. Nonstructural and structural
carbohydrates. Large Dairy Herd Management.
Mgt. Services, American Dairy Science
Association. 25:219.

Nocek, J. E. 1993. Manipulating nonstructural and
structural carbohydrates in rations for dairy cattle.
Proc., Fl. Ruminant Nutr. Symp.

Page 4

Nonstructural and Structural Carbohydrates in Dairy Cattle Rations

Table 5. Carbohydrate composition of selected feedstuffs for adjusted NDF and NSC values for use in
fnrmol latinn ratinne


Alfalfa pellets 46
Alfalfa hay, midbloom 46
Barley, grain 19
Barley malt sprout pellets 44
Beet pulp 54
Bermudagrass hay 72
Bermudagrass silage 68
Brewers' grains 46
Canola meal 26
Citrus pulp 23
Corn, ground 9
Corn silage 51
Corn gluten feed 45
Com gluten meal 14
Corn distillers' grains 43
Cottonseed meal 28
Cottonseed hulls 90
Cottonseed, whole 44
Hominy feed 23
Milo, ground 14
Molasses, cane 3
Oats, rolled 32
Oat silage 49
Pangolagrass hay 70
Perennial peanut hay 54
Peanut skins 28
Peanut meal 17
Peanut hulls, coarse 74
Potato meal 6
Rice bran 33
Rye silage 58
Sorghum silage 58
Soybean hulls 67
Soybeans, whole 10
Soybean meal 11
Wheat midds 37
Wheat, grain 13
1ANDF = adjusted neutral detergent fiber; AV = adjusted value.
# EE + Ash + CP); ANDF = (AV X NDF).
-NSC values modified from Mertens values.

% dry matter -
.32 15 22
1.00 46 24
.65 12 63
.43 19 25
.35 19 40
1.10 79 2
1.00 68 6
.40 18 13
.55 14 13
.90 21 60
1.00 9 74
.90 46 35
.40 18 30
.90 13 19
.40 17 18
.50 14 17
.90 81 2
.80 35 5
.50 12 65
.90 13 69
1.00 3 70
.40 13 46
1.00 49 31
1.00 70 8
1.00 54 26
.80 22 30
.80 14 21
1.00 74 2
1.00 6 76
.50 17 25
1.00 58 17
1.00 58 24
.35 23 14
.80 8 23
.90 10 27
.45 17 35
.90 12 17
NSC (nonstructural carbohydrate) = 100-(NDF

Page 5

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