Advanced Series in Agricultural Sciences 7

Co-ordinating Editor: B. Varon, Bet-Dagan
Editors: D.F.R.Bommer, Rome
G.W.Thomas, Lexington
L. D. Van Vleck, Ithaca

B.R.Sabey, Fort Collins

Y.Vaadia, Bet-Dagan

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John K. Matsushima

Feeding Beef Cattle
With 31 Figures

Springer-Verlag
Berlin Heidelberg New York 1979

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Professor JOHN K. MATSUSHIMA
Department of Animal Sciences
Colorado State University
Fort Collins, CO 80523, USA

ISBN-13: 978-3-642-67201-9
DOl: 10.1007/978-3-642-67199-9

e-1SBN-13: 978-3-642-67199-9

This work is subject to copyright. All rights are reserved, whether the whole or part of the material
is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under § 54 of the
German Copyright Law where copies are made for other than private use, a fee is payable to the
publisher, the amount of the fee to be determined by agreement with the publisher.
© by Springer-Verlag Berlin· Heidelberg 1979.
Softcover reprint of the hardcover lst edition 1979
The use of registered names, trademarks, etc. in this publication does not imply, even in the absence
of a specific statement, that such names are exempt from the relevant protective laws and regulations
and therefore free for general use.
2131/3130-543210

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Preface

The purpose of this book is to provide the reader with some basic
information applicable to cattle feeding. It is intended to adapt some of
the basic principles of nutrition in applied form.
During the past few decades there have been various changes in type
and form of feeds available for livestock feeding due to new kinds of
equipment. Mechanization has made it possible to perform certain operations of the beef production program more efficiently and economically.
With all the new innovations and advances in animal nutrition combined
with the capabilities of the computer, it becomes very challenging for
everyone to keep up to date on the latest information in the field of

cattle feeding and production.
The text was written with the intent of utilizing the raw materials,
facilities, equipment, etc. which are available in the United States. The
terminology of certain materials such as feed ingredients will vary from
one country to another. One term which is frequently used in this text is
forage. Although the term roughage is used more commonly in the United
States it has been replaced with forage in this text.

Fort Collins, January 1979

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J.K.

MATSUSHIMA


Contents

Chapter 1

1.1
1.1.1
1.1.2
1.1.2.1
1.1.2.2
1.1.2.3
1.2
1.2.1
1.2.2

1.2.3
1.3

1.4

1.5
1.6
1.6.1
1.6.1.1
1.6.1.2
1.6.1.3
1.6.1.4
1.6.2

1

Proximate Feed Analysis
Chemical Classification of Nutrients
Water
Drinking Water
.... ....
Moisture Content of Feed and Diet
Effect of Moisture Content of Feed or Diet on Animal
Performance
...................
Effect of Moisture Content on Feed and Storage Qualities
Effect of Moisture Content When Purchasing Large
Quantities of Feed
Protein . . . . . . . . . .
Digestible Protein

.... .
Choice of Protein Supplements
Nonprotein Nitrogen Sources
Fats
......... .
Carbohydrates . . . . . .
Nonprotein Nitrogen (NPN)
Efficient Use of Urea
Urea Supplements fpr Various Feeding Conditions and
Weights of Cattle . . . . . . . . . . . . . . . . . .
For Weanling Calves
................
For Wintering Calves Over 500 lbs, for Replacement Heifers,
and Young Bulls . . . . . . . . . . . . . . . .
For Pregnant or Dry Cows on Pasture and in Drylot
For Feedlot Cattle on High Energy Rations
Ammonia Toxicity . . . . . . . . .
References and Supplemental Literature

Chapter 2
2.1
2.1.1
2.1.1.1
2.1.1.2
2.1.1.3
2.1.2
2.1.2.1

Nutrients


Classification of Feeds

Forages..
Dry Forages
Legumes . .
Other Legumes
N onlegumes .
Green or Succulent Forages.
Silages. . . . . . . . . .

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1

2
3
3
5
5
7
7
8
8
9
9
10
10
11
11
12

13
13
14
14
15
16
19
19
19
19
21

22
23
23


VIII

2.1.2.2
2.1.2.3
2.1.2.4
2.1.2.5
2.2
2.2.1
2.2.1.1
2.2.1.2
2.2.1.3
2.2.1.4
2.2.2

2.2.3

Contents

Corn and Sorghum Silages
Silage Preservatives .
Haylage . . . . . .
Soilage (Green Chop).
Concentrates....
Low Protein Concentrates (Less than 15% Protein) .
Cereal Grains .
Molasses. . . .
Beet Pulp. . . .
Mill Byproducts .
Medium Protein Concentrates (15-25 % Protein)
High Protein Concentrates (Over 25 % Protein)
References and Supplemental Literature. . . .

Chapter 3
3.1
3.1.1
3.2
3.2.1
3.2.2

Balancing Rations. . . . . . . .
Information or Materials Needed .
Procedure for Formulating Rations.
Formulating a Simple Ration Involving Two or Three Feeds
Formulating a Ration with Specific Concentrate Level.

References and Supplemental Literature . . . . . . . .

Chapter 4
4.1
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6
4.1.7
4.1.8
4.2
4.2.1
4.2.2
4.2.3

Processing Feeds for Beef Cattle

Methods of Processing . . . . . .
Grinding, Cracking, or Dry Rolling.
Extruding.
Pelleting
Roasting.
Popping .
Micronizing.
Steam Rolling.
Steam Flaking; Pressure Flaking.
High-Moisture Grains; Reconstituting
Soaking .

Sprouting . . . . . . . . . . . . .
Exploding . . . . . . . . . . . .
References and Supplemental Literature.

Chapter 5
5.1
5.2

Procedures in Ration Formulation.

Systems of Feeding .

Pasture Feeding .
Growing Cattle .

24
26
27
27
28
28
28
34
35
36
36
38
41
43


44
44
44
44
48
80
81
81
83
83
84
84
85
85
86
86
88
89
89

90
90
93
93
95

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Contents


5.2.1
5.2.1.1
5.2.1.2
5.2.1.3
5.2.2
5.3
5.3.1
5.3.2
5.3.2.1
5.3.2.2
5.3.3
5.3.3.1
5.3.3.2
5.3.4
5.3.4.1
5.3.5
5.3.6
5.3.7

IX

Feeding Replacement Heifers . . . . . .
Protein. . . . . . . . . . . . . . . .
Minerals (Calcium, Phosphorus, and Salt)
Vitamin A . . . . . . . . . . . . . .
Feeding Replacement Feeder Cattle (Backgrounding) .
Finishing Cattle. . . . . .
Concentrate-to-Forage Ratio
Substitution of Feeds.

Grains. . . . . . . . .
Forages . . . . . . . .
Protein Levels and Sources
For Finishing Lightweight Feeders.
For Finishing Yearling Cattle
Mineral Supplementation.
Salt (NaCl) ... . . . . . .
Calcium and Phosphorus. .
Potassium and Other Elements.
Vitamin A Supplementation. .
References and Supplemental Literature.

Chapter 6
6.1
6.1.1
6.1.2
6.1.3
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9

Antibiotics . . . .
For Young Calves.
For Feedlot Cattle.
For Range Cows and Bulls

Anthelmintics. .
Bloat Prevention.
Coccidiostat
Foot Rot . . . .
Grubicide . . .
Melengestrol Acetate.
Rumensin . . . . .
Stilbestrol . . . . .
References and Supplemental Literature.

Chapter 7
7.1
7.1.1
7.1.2
7.2
7.3

Feed Additives.

Gtowth Stimulants.

Stilbestrol Implants
For Range Cattle .
For Feedlot Cattle.
Synovex Implants .
Ralgro Implants. .
References and Supplemental Literature.

Subject Index


.
.
.
.
.
.
.
.
.
.
.
.
.
.

96
96
97
98
98
100
101
103
103
103
104
104
104
105
105

105
106
106
107

· 108
·
·
·
·
·
·
·
·
·
·
·
·
·

108
116
116
117
117
117
118
118
119
119

119
120
121

· 122
·
·
·
·
·
·

122
122
122
124
124
125

· 126

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Chapter 1

Nutrients

A nutrient is defined by Morrison (1959) as "any feed constituent, or group of feed
constituents of the same general chemical composition which aids in the support

of animal life." The six basic nutrients which are found in varying quantities in
animal feeds include: (1) water, (2) ash, (3) protein, (4) fat, (5) crude fiber, and
(6) nitrogen-free extract. These nutrients in the feeds do not necessarily satisfy the
nutritional requirements of the animal. For example, the vitamins mayor may
not be present in adequate quantities in the feed or synthesized adequately in the
body to meet the requirements for proper production or animal performance. In
certain cases if an animal is fed a variety or certain combination of feeds, the
nutritional requirements may be met. However, there are situations where a
deficiency of a given nutrient can be overcome at a cheaper cost without increasing the total volume of the diet. These nutrients which are added to the diet,
usually in highly concentrated form, are referred to as supplements.

Proximate Feed Analysis
For a given feed the nutrient content will vary from one batch to another. There
are many different causes which vary these nutrient contents. Visual appraisal of a
feed may not give an accurate estimate of its feed value. Under certain circumstances it would be desirable to have a feed sample sent to a laboratory to have it
Feed
(100%)

/~

Moisture
(12%)

Dry matter
(88%)

------ ------

Ash (inorganic
matter)

(5%)

/

Organic matter
(83%)

Protein
(13%)

______

Nonnitrogenous
matters
(70%)

----- -----

Carbohydrate
~----(66%)

Fat

(4%)

Fig.l. Components in inorganic and
organic portions of dry matter

Crude fiber
(10%)


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Nitrogenfree extract
(56%)


Nutrients

2

analyzed. The diagram of nutrients (Fig. 1) with numerical values in parenthesis
may be helpful to interpret a feed analysis report. For example, if the laboratory
report shows 88% dry matter, the moisture or water content of the feed is 12%.

Chemical Classification of Nutrients
The proximate analysis for the six basic nutrients does not distinguish the various
components of a nutrient. For example, the ash content of a feed or ration does
not tell the amount of calcium, phosphorus or any other element, nor does the
crude protein analysis indicate how much urea or nonprotein nitrogen is present
in the feed or ration. Figure 1 gives a list of various components that may be
present in the inorganic and organic portions of the dry matter; Table 1 gives the
chemical analysis.
Table 1. Chemical analysis scheme of inorganic and organic nutrients
Essential
elements

------cMacro-[~i ~I

Inorganic

(ash)
-----1

'
Micro -[Co, Fe, Zn, I, Mn,
K, S, Mg, Cu, Mo

_ Probably--[FI, Se,
essential
Br, Ba
Probably ---[Cu, Se,
toxic
FI, Mo
Tryptophan, histidine,

Essential
amino acids
Protein

-{
.

iaq~inine, t~reonine,
Iysme, Ieucme,
isoleucine, valine,
methionine,
phenylalanine

Glutamic acid, ala-


No~esse~tJal -{nine, serine, proline,

Nitrogenous

ammo aCIds

aspartic acid

Nonprotein-{urea, biuret, amines
nitrogen
free-amino acids
Organic

Simple----Fattyacids
Lipids - { Compound - Neutral fats, sterols
Pseudo ---- Vitamins A, D, E, K, carotene

Carbohydrates

{

Crude fiber

--C Polysaccharides -- cellulose, hemicellul.

.
iMonosaCCharides -- simple sugars
Nltrogenfree
Pol saccharides --- starches
extract

y
.
Water-soluble----vitamm C,
vitamins
B-vitamins

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Drinking Water

3

1.1 Water
Water is occasionally referred to as moisture, particularly when reference is made
to the nondry matter portion of the feed. The moisture content of feeds has
various implications on the quality of feeds, feed storage, daily consumption of
diet by cattle etc., while quality and quantity of drinking water available to cattle
may have direct bearing on the health and performance of animals (Fig. 2). Therefore, the discussion on this nutrient will be divided into two categories.

1.1.1 Drinking Water
The requirements for water by the animal are just as important, perhaps more so
than for protein, energy, minerals and vitamins. However, feeding standards do
not include the water requirement for animals, probably because of several uncontrollable or variable factors such as air and water temperature, humidity,

Fig. 2. Water is extremely important. An adequate supply of good quality water keeps the
animals in good health and aids in the utilization of other nutrients. (Photo: courtesy Gary S.
Null)

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Nutrients

4

Fig. 3. Water consumption of European
and Indian cattle as affected by increasing
temperatures. (After Winchester and Morris, 1956)

2 .00

1.50

EUROPEAN CATTLE
(Bos taurus)

___

1.00

0 .50

~ INDIAN CATTLE
(Bos indicus)

OL-~--~--~--~~--~

40 50 60 70 80 90 100
AMBIENT TEMPERATURE (oF)


*PER POUND OF DRY MATTER INGESTED

moisture, protein and salt content of the ration, breed of cattle, frequency of
watering, physiological condition ofthe animal, and quality of water.
Figure 3 illustrates the water consumption of European and Indian cattle as
affected by increasing temperatures. The Brahama-type cattle apparently have
lower water requirements than English breeds as air temperature increases.
When salt (NaCl) is force-fed in the diet it will increase water consumption.
Marked water consumption by feedlot cattle is noticeable when the salt concentration in the diet exceeds 1% (dry matter basis) or 4 oz. (115 g) per head daily.
Water quality may affect water consumption. When the total solids in water
exceed 15,000-17,000 mgll (1.5-1.7% total solids), the performance of animals
may start to decrease. This is probably a result of the decreased water consumption. High salt content, usually 1% or higher, in drinking water will also decrease
water consumption. With sulfates a level over 1 gil may cause diarrhea and, in the
case of nitrates, levels of 100-200 ppm may be toxic.
Water Requirements. The water requirements of animals are met from three
sources, (1) drinking water, (2) water contained in the feed, and (3) the metabolic
water that is formed within the body as a result of oxidation in the tissues. The
latter source is important from the standpoint of water conservation, since the
catabolism of 1 kg of fat, carbohydrate or protein gives rise respectively to the
formation of about 1190,560 or 450 g of water.
The quantity of water consumption by beef cattle will range from one to one
and a half gallons per 100lbs bodyweight or 8.4-12.51 per 100 kg bodyweight.

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Effect of Moisture Content of Feed or Diet on Animal Performance

5


Table 2. Water intake by cattle according to dry matter consumption. (From Agr. Res.
Council, 1965)
Class of Stock

Environmental
temperature

CC)

Calves
(first 5-6 weeks of life)

Water intake
(kg/kg dry
matter consumed)

6.5

Cattle
(above 100 kg, not pregnant and not lactating)

-17 to + 10°
10-15°
15-21°
21-27"
above 27°

3.5
3.6


4.1

4.7
5.5

The British Agricultural Research Council publication suggests that water intakes
to meet requirements depend on dry matter intake. The figures are noted in
Table 2.

1.1.2 Moisture Content of Feed and Diet
1.1.2.1 Effect of Moisture Content ofF eed or Diet on Animal Performance

When certain feeds, such as silages, are high in moisture content and fed in large
quantities, it appears that this condition affects dry matter intake. In feedlot
rations where cattle are fed high-moisture ensiled grain (30-35% moisture) with
silage as the major forage, the dry matter consumption is usually lower than when
dry grain is fed. Whether the lower dry matter consumption is due to the moisture
content of the high moisture grain, or whether it is due to differences in volatile
fatty acid or pH content between ensiled and dry grain has not been verified.
Extremely dry rations create dust problems. Addition of water to such rations
would overcome such a problem. Also, moist rations usually prevent fine powdery material separation from coarser materials. If feed intake is directly related
to the dry matter content of the ration, what is the maximum level of moisture
that can be present in the ration without affecting feed consumption and animal
performance? Experimental data with feedlot cattle on a high concentrate diet
where tap water was added to bring the moisture level in the diet to 35% had no
significant effect on dry matter consumption, animal performance, dry matter and
nitrogen disappearance in the digestive system or digesta or fecal pH values
(Fig. 4). The data is presented in Table 3.
The data presented in Table 4 reveal that adding water to the ration just prior

to feeding does not necessarily influence dry matter intake. The reason for this is,
perhaps, explained by the data shown in Table 5, which reveal that if the ration is
low in moisture the animals will drink more water, and conversely if the ration is
high in moisture.

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6

Nutrients
Fig. 4. When extremely dry
rations or finely ground feeds
are fed to cattle they will have a
tendency to short their feed.
The above photo shows a ration that is well mixed and
combines chopped hay and a
small quantity of silage so that
the ration is not excessively dry
or dusty. (Photo: courtesy Bill
Fleming)

Table 3. Effect of adding tap water to a high concentrate feedlot ration"
Percent moisture in ration

15%
(control)

Avg. dry matter consumed per day, lbs:
First 41 days

Last 78 days
Total 119 days
Avg. weight of cattle, lbs:
Initial weight
41-day weight
Final weight
Avg. daily gain, lbs:
First 41 days b
Last 78 days b
Total 119 days
Avg. feed rcquired/lb gain:
First 41 days
Last 78 days
Total 119 days

18.56
21.91
20.79
751
857
1,102

25%

18.72
22.05
20.88
751
866
1,088


35%

18.08
21.21
20.13
751
844
1,084

2.58 1. 2
3.15 1
2.95

2.821
2.84 2
2.83

2.27
3.09
2.80

7.20
6.95
7.04

6.63
7.75
7.40


7.96
6.87
7.19

" The following data was taken from Gen. SeI. Pub!. 934, Colo. Expt!. Station. Each
treatment involved 45 steers.
b Means in the same row not possessing the same superscript. differ significantly (P<0.05).

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7

Effect of Moisture Content When Purchasing Large Quantities of Feed

Table 4. Dry matter consumption, apparent dry matter and nitrogen disappearances, and
digesta pH values as affected by water addition to rations
Percent moisture in ration

15%
(control)

25%

35%

Avg. dry matter of consumed ration, % b
Apparent dry matter disappearance, %
Rumen
Small intestine and cecum

Colon and rectum
Entire tract
Apparent N disappearance, %
Rumen
Small intestine and cecum
Colon and rectum
Entire tract
Avg. digesta pH values
Rumen
Abomasum
Cecum
Feces

83.6F

69.19 2

54.323

45.21
36.64
2.96
85.73

44.45
36.26
3.91
84.54

45.89

35.46
2.97
84.29

- 2.84
72.86
3.33
74.99

3.66
66.74
4.44
74.77

2.31
68.86
2.61
73.89

5.97
2.49
6.77
6.79

5.99
2.47
6.78
6.90

5.96

2.32
6.83
6.85

s Data taken from Gen. Ser. Publ. 934, Colo. Exptl. Station.
b Means in the same row not possessing the same superscripts differ significantly (P
Table 5. Average daily water consumption by feedlot cattle that are fed rations containing
different quantities of added tap water just prior to feeding, per head basis
Percent moisture in ration

15%

35%

45%

Drinking water consumption daily, g
Tap water added to ration, g
Moisture from natural feed, g
Total water intake, g

13,691
None
1,162

12,703
1,319
1,040
15,062

10,331
3,212
967
14,510

14,853

1.1.2.2 Effect of Moisture Content on Feed and Storage Qualities

Unless high moisture feeds are to be fed to livestock immediately or within one or
two days, they will start to heat and may cause internal combustion or if they do
not heat very much, they may eventually mold. In order to keep feed from
molding or spoiling, the moisture content should be less than 15% under most
conditions.
1.1.2.3 Effect of Moisture Content When Purchasing Large Quantities ofFeed

The feedlot industry relies heavily on purchased feeds, particularly the grains.
Bids are quoted on the quality of grain, i.e., grade number 2, 3 etc. Quite often one
does not recognize the tremendous difference in the cost of grains of the same
quality grade but with a difference in moisture content. An example is shown in

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Nutrients

8

Table 6. Extra cost to finish a steer with grain of different moisture content a

Cost/cwt
of 88% dry
matter grain
$3.00
$ 3.50
$4.00
$4.50
$ 5.00
$ 5.50
$6.00

Amount of grain equivalence on dry matter basisb
88%
2,000 Ibs

87%
2,0231bs

86%
2,0471bs

85%
2,0711bs

$ 60.00
70.00
80.00
90.00
100.00
110.00

120.00

$ 60.69
70.81
80.92
91.04
101.15
111.27
121.38

$ 61.41
71.65
81.88
92.12
102.35
112.59
122.82

$ 62.13
72.49
82.84
93.20
103.55
113.91
124.26

The assumption is that a steer will consume 2000 Ibs of grain during the feeding period.
2,000 Ibs of grain with 88% dry matter furnishes 1,7601bs dry matter, thus, it will require
2,0231bs of 87% dry matter grain to furnish 1,760 Ibs dry matter.
a

b

Table 6. The illustration shows that if grain is bought at $ 120 per ton with a dry
matter content of 88% and that it takes 2000lbs of the grain to get a steer to
market, it will probably take 2071lbs of grain which has 85% dry matter. Thus,
instead of having' $ 120 for the grain cost they will be increased to $ 124.26.

1.2 Protein
Crude protein value of a feed or ration is obtained by multiplying the nitrogen
content by the factor of 6.25. Thus it is possible to obtain a figure exceeding 100%.
For example, urea used in ruminant feeds contains approximately 44.8% nitrogen
or 280% crude protein (44.8 x 6.25).
It has been stated and reported in many publications that protein quality is of
little significance in ruminant nutrition since polygastric animals can synthesize
the essential amino acids. The latter part of the statement is true, but it should be
emphasized that rumen bacteria influence the utilization of different nitrogen
sources. Furthermore, the utilization of nitrogen is dependent upon the time lag
between the point of introduction into the rumen and microbial protein synthesis.
Therefore, the adaptation of the microflora in the rumen to nitrogen sources of
. poor quality protein (those devoid of or low in essential amino acids) is an
important consideration in deciding what kinds or types of protein supplements
might be used with rations or feeds which are inadequate in protein (Fig. 5).

1.2.1 Digestible Protein
Digestible protein values are listed frequently for individual feeds. Probably a
large majority of the digestible protein values are fairly accurate. However, there
are so many factors which affect the digestion coefficients. Since published average digestibility coefficients of feeding stuffs have been determined mainly at low

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Nonprotein Nitrogen Sources

9

Fig. 5. In order to determine the digestion coefficients of nutrients, such a protein, it is
necessary to know the quantity of nutrient consumed and excreted. Research trials that are
conducted with facilities as shown above enable scientists to determine accurately the value
of feeds when fed singly or in combination with other feeds

planes of nutrition, they are probably several percent too high when applied to
full-fed animals. The available evidence in the literature indicates that increased
levels of feed intake are generally associated with a depression in digestibility.
Therefore, if digestible protein values for different feeds are used, there may be
wide discrepancies when attempting to formulate rations on the basis of digestible
protein or crude protein basis. The most common practice today by most nutritionists and feedlot consultants is to use the crude protein values.

1.2.2 Choice of Protein Supplements
Ordinarily the major criteria in selecting a protein supplement depends upon the
cost per unit of protein. For example, if cottonseed meal is priced at $ 200 per ton
with a guarantee of 45% crude protein, and soybean meal is $ 210 per ton with
46% crude protein, the price advantage would go to cottonseed meal because
each pound of protein in cottonseed meal costs 22.2 cents, while a pound of
protein in soybean meal costs 22.8 cents ($ 210--;.- 2000 lbs= $1O.50/cwt;
$ 10.50--;.- 46 lbs = 22.8).

1.2.3 Nonprotein Nitrogen Sources
Urea and other similar compounds which contain an abundance of nitrogen can
be used advantageously to meet the protein needs of cattle. Some of the limitations or drawbacks of nonprotein nitrogen compounds should be considered for

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Nutrients

10

their use. The nonprotein nitrogen compounds are to cheapen the cost of rations.
It must be recognized that the nonprotein nitrogen compounds do not furnish
any energy in contrast to the preformed protein supplements such as cottonseed
meal, soybean meal etc. Furthermore, they do not furnish other nutrients, such as
minerals or vitamins.

1.3 Fats
Ordinary fats in plant and animal tissues when combusted produce nearly
2.25 times more calorie or energy than proteins or carbohydrates. However, in
cattle rations there are several restrictions to the addition or use of high levels of
fat. Rations composed of common ingredients which are generally fed very frequently provide over 3-4% fat or ether extract on dry matter basis. Addition of
vegetable oils or animal fats in feedlot rations seldom has any effect on the body
fat characteristic. The primary adverse effect of adding excess levels of either plant
or animal fat is due to the digestive problems which are encountered.
In order to prevent dust in extremely dry rations, or to increase the energy
content of the ration, the maximum quantity of supplemental fat to include in the
ration should not exceed 5% by weight on dry matter basis.
Occasionally animal fats become competitive with cereal grains as a source of
energy for feedlot cattle. The recommended level is between 3 and 5%, which is in
addition to the fat already present in the ration. A rule of thumb to follow to
determine how much a feeder can afford to pay for the supplemental fat is
2.5 times the cost of grain (e.g., if corn is priced at 5 cents per pound, the affordable price for fat would be 12.5 cents per pound).

1.4 Carbohydrates
Crude fiber and nitrogen-free extract make up the carbohydrate portion of a feed
or ration. To evaluate a feed on the basis of its carbohydrate content may be
misleading. The following example (Fig. 6) indicates that Feed A would be a superior feed in terms of energy value because of its higher carbohydrate content.
However, the lower crude fiber content in Feed B would rate it as a superior feed
as far as energy potential is concerned.
Starches and sugars supply the readily available energy to cattle. Since sugars
are readily fermentable in the rumen, the microbes cannot use excessive quanti-

Feed

Dry
matter

Crude
fiber

Nitrogenfree
extract

Carbohydrate

A
B

90.0
90.0

29.0

2.0

36.0
60.0

65.0
62.0

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Fig.6. Comparison of two
feeds as a source of energy


Efficient Use of Urea

11

ties. A discussion is presented elsewhere in this publication on the feeding of
molasses, which is basically composed of sugars.
Crude fiber is important in giving bulk to feedlot finishing rations. Bulk is
generally referred to as the weight of a given volume of feed. Forages are high in
crude fiber, but if these feeds are finely ground the bulk characteristic is decreased.
Concentrates, on the other hand, are low in crude fiber and therefore in their
natural form would tend to lack the bulk characteristic. Processing concentrates
by special methods, such as flaking (described elsewhere in this publication), can
change the bulk density of such feeds.

1.5 Nonprotein Nitrogen (NPN)
Werske et al. (1879) reported that ruminants could convert nonprotein nitrogen

to protein. Hart et al. (1939) reported that either urea or ammonium carbonate
was used by dairy heifers. They also found that dietary soluble carbohydrates
increased NPN utilization. Loosli et al. (1949) found that the ten essential amino
acids could be synthesized in the rumen by feeding lambs a synthetic diet containingNPN.
Urea was approved in the United States as a feed ingredient in ruminant diets
in 1940 by the Association of American Feed Control officials.
Ammonia is the common denominator in the utilization of NPN by ruminants (Hungate). If the rumen microorganisms cannot degrade the urea to yield
free ammonia, it is useless as a nitrogen source to the microorganisms. The
following steps appear to be involved in its complete utilization (Nat. Acad. Sci.,
1976) :
1. Urea ~NH
urease
3 +CO.
2
2. Carbohydrates :!~~a;:::l) volatile fatty acids + keto acids.
3. NH3 + keto acids :~~~O!~:l) amino acids.

4. Amino acids ~
microbial protein.
enzymes
5. Microbial protein animal enzymes;n t h e ) free amino acids.
abomasum and smal intestines

6. Free amino acids are absorbed from the small intestine and used by the host
animal.

1.6 Efficient Use of Urea
Since the bacteria in the rumen must utilize the ammonia from urea, it is important to satisfy the nutritional needs of the rumen microflora. Energy and minerals
must be included in the diet in proper quantities for the bacteria to make efficient
use of the ammonia. Thus, urea in beef cattle rations is used more effectively in

high concentrate rations than high forage rations. The starch from cereal grains
or sugars that are present in molasses provide the energy for the bacteria. Fats
(lipids) are also important sources of energy, but the long chain fatty acids arising

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12

Nutrients

Fig. 7. Urea may be included in a dry or liquid supplement for either feedlot cattle (shown
above) high energy ration, or to range cattle to furnish part of the nitrogen for rumen microbial

protein synthesis. (Photo: courtesy Allied Chemical Corp.)

from the hydrolysis of lipids are not used very effectively by rumen microbes
(Fig. 7).
Sulfur is essential in maximizing the efficient utilization of urea nitrogen. The
optimum N:S ratio appears to be around 15: 1. Apparently organic sulfur can be
used, as well as inorganic sources.
Trace mineralized salt is recommended on a free-choice basis. Research data
do not indicate what trace elements and what quantities of certain trace elements
are beneficial or toxic. Thus, force feeding of trace mineral supplements on a
routine daily basis appears questionable at this time.
Quite often under range conditions when the protein supplements are fed once
daily and in situations when supplemental hay must be fed, it is recommended
that the hay be fed first before the protein supplement. This will usually give the
less aggressive cattle a greater opportunity to get their share of protein supplement. Also, there is a possibility that urea toxicity may be reduced in very aggressive cows which may consume more urea than is safe.

1.6.1 Urea Supplements for Various Feeding Conditions
and Weights of Cattle
Because urea is highly soluble and the ammonia is released very rapidly in the
rumen, the quantity of urea present in the protein supplement is very important.
Furthermore, the substitution of urea for natural protein supplements implies
that urea must be converted to microbial protein before the urea nitrogen be-

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For Wintering Calves Over 500 lbs, for Replacement Heifers, and Young Bulls

13

comes of any value to the host animal - the cattle. Young calves which posses
nonfunctional rumen have limited microflora to utilize the urea nitrogen to meet
the protein needs. Animals on high fibrous diets with limited energy OJ; minerals
would not be able to utilize urea nitrogen very effectively unless proper conditions
are met. Also, the fact that it generally takes from two to three weeks for the
microbes to make adaptations to drastic changes in diets, particularly from high
to low fiber diets and from preformed dietary protein to nonprotein sources, it is
recommended that adjustments be made gradually. It is imperative that the manufacturer of protein supplements, the feedlot operator, the rancher or anyone else
who uses nonprotein nitrogen supplements is familiar with the proper levels that
can be fed for efficient use and what management guidelines must be exercised.
1.6.1.1 For Weanling Calves

Weanling calves weighing from 300lbs to around 400lbs should not be fed protein supplements containing urea. Low levels of urea in the protein supplement
may not necessarily kill the animals, but could have an adverse effect on their
performance. When the rumen microflora cannot utilize the urea nitrogen effectively, the gains will be lower and less economical, as indicated by their lack-luster
hair coat.

Since the protein requirement for weanling calves varies from 8.5% to nearly
18%, depending upon the weight and expected gain, it should be readily apparent
that a protein supplement containing a high level of urea would adversely affect
the protein utilization.
It is recommended that weanling calves, regardless of weight, be fed a natural
protein supplement such as cottonseed meal, soybean meal, linseed meal etc. for
at least 60--90 days before any urea-containing supplement is introduced.
1.6.1.2 For ft'intering Calves Over 500 lbs, for Replacement H elfers, and Young
Bulls

Animals which have been weaned for three or four months and have access to
plenty of forage may be fed a protein supplement which contains urea. The level
of urea should be limited to less than O.llb (45 g) per head daily. This means that
if this quantity of urea does not satisfy the protein requirement, the remainder of
the protein must come from a natural supplement.
The following example is shown to illustrate a situation where a rancher has
500 lb (225 kg) replacement heifers on winter pasture which contains 6% protein
on dry matter basis. If these heifers are required to gain approximately 1.0lb
(0.5 kg) daily, the heifers require a 9.5% protein diet with a daily intake of approximately l4.3lbs (6.5 kg) of dry matter. Thus, the rancher will have to feed approximately lIb of supplement containing 56% protein. If this protein supplement
contains 10% urea, the heifers would get O.llb urea per head daily.
Solution:

*

14.31b dry matter requirement x 9,5 %= 1.36lbs protein
-13.3 lb dry matter from pasture x 6 %= 0.80
1.0 lb protein supplement*
x 56%=0.56

See p.97 for illustrations on the interpretation of protein supplements which contain urea.

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14

Nutrients

In the event that the pasture condition is such that the animals will not have
adequate feed, or when the forage is covered with snow so that feed supply is
limited, it is recommended that a protein supplement without urea be used.
1.6.1.3 For Pregnant or Dry Cows on Pasture and in Drylot

The decision to use a protein supplement with or without urea will depend on the
forage available and the amount of readily available energy is the supplement.
Under most conditions a rancher will not feed 2 or 3lbs of grain. Therefore, in
situations where the cows receive readily available energy and to be sure that the
very aggressive animals can be fed to stay within the nontoxic level of urea, a
urea-containing supplement can be used. Under practical conditions it is desirable to figure about O.3--O.4lb (135-180 g) of urea as the maximum possibility that
a cow could consume within a period of 15 min or less (Fig. 8).
In drylot where the cows have continual access to feed and the protein supplement is thoroughly mixed with the other ingredients, it is possible to feed up to
O.4lb (180 g) urea per head daily. Usually when the level of urea exceeds 0.21b
(90 g) the feed intake will be reduced.
1.6.1.4 F or Feedlot Cattle on High Energy Rations

Feeder cattle coming into the feedlot directly from pasture or all-roughage diets
will not respond as well on rations supplemented with a high level of urea as cattle

Fig. 8. Urea may be fed free-choice in a liquid supplement. Molasses is used as a carrier
for the urea. (Photo: courtesy Allied Chemical Corp.)

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Ammonia Toxicity

15

fed a nonurea supplement. Feed intake will be lower, and liveweight gains will
correspond. In some instances the cattle on urea supplement will catch up in
weight, so that at the end of the feeding period no difference in performance will
be realized.
When practical, it is recommended that a natural protein supplement be fed
for about two weeks and then a urea-containing supplement be introduced. Once
the urea-containing supplement is introduced into the ration, the level of urea can
be increased to about O.2lb (90 g) per head daily. This level can be nearly doubled
without fear of toxicity, but feed intake will decrease markedly. The ration apparently becomes unpalatable to the animals when the level exceeds 0.2 lb daily.

1.6.2 Ammonia Toxicity
Feeding of high levels of dietary urea may result in rapid accumulation of ammonia in rumen fluid. This causes a rapid rise in rumen pH and rapid absorption
of ammonia across the rumen wall. When the rate of ammonia absorption exceeds the capacity of the liver to convert it to urea, ammonia accumulates in the
blood and toxicity may result.
Acute ammonia toxicity symptoms appear to be progressive as follows:
a)
b)
c)
d)
e)
f)

g)
h)
i)
j)

nervousness and uneasiness,
excessive salivation,
muscular tremors,
incoordination,
difficult breathing,
frequent urination and defacation,
front legs stiffen and animal becomes prostrate,
violent struggling, bellowing,
bloating is common,
death occurs within 0.5 to 2.5 h after initial symptoms are observed.

Predisposing factors to urea toxicity to cattle appear to be:
a)
b)
c)
d)
e)

lack of adequate adaptation to urea,
fasting prior to urea consumption,
feeding urea with poor quality roughage,
feeding diets which promoted a high pH in ruminal fluid,
low water intake.

Effective treatment for urea toxicity, if applied before tetanic spasms occur, is

immediately to administer 5-10 gallons (20-401) of cold water orally. Cold water
will lower ruminal fluid temperature and thereby reduce ureolyses. It will dilute
the concentration of ammonia and reduce its rate of absorption from the rumen.
Four liters of either dilute acetic acid or vinegar given with cold water is more
effective than cold water alone. Acetic acid will neutralize the toxic effects of free
ammonia.

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16

Nutrients

References and Supplemental Literature
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Esplin, Grant, Hale, W. H., Hubbert, F., Jr., Taylor, B.: Effect of animal tallow and hydrolyzed vegetable and animal fat on ration utilization and rumen volatile fatty acid production with fattening steers. J. Animal Sci. 22, 695 (1963)
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References and Supplemental Literature

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Garrett, W. N., Mendel, V. E.: The effect of fat on the concentrate to roughage ratio selected
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protein, and an antibiotic on performance, carcass characteristics, rumen environment,
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