ANHYDROUS AMMONIA VERSUS UREA IN
CORN SILAGE FOR DAIRY ANIMALS

Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY
ODON P. SANTANA
1969

 

 

ABSTRACT

ANHYDROUS AMMONIA VERSUS UREA IN CORN
SILAGE FOR DAIRY ANIMALS

BY

Odon P. Santana

Corn silage was ensiled alone or with additions
of urea or ammonia and several criteria were used to
evaluate these chemical additives.

In a series of feeding trials over a two-year
period the NPN-treated corn silages containing 32.6 to
52.4%.dry matter (D.M.) were fed as the only forage to
Holstein heifers and lactating Holstein cows to compare
their nutritive value.

Effects of drying temperatures and time of ex-
posure to the barn atmosphere on nitrogen concentration
of corn silages were also studied.

The crude protein equivalent of the urea-treated
silages (0.5 and 0.75%) at 36 and 52% D.M. increased

1

Odon P. Santana

4.1 and 4.2 percentage units on a dry basis. silages
containing ammonia (0.28%) increased in crude protein
equivalent by 3.6 and 1.8 percentage units on a dry basis.
for the 36 and 41%.D.M4 levels. respectively.

Heifers fed ammoniated silage as the sole feed
in which ammonia furnished 31.7% of the total ration
nitrogen made adequate body weight gains. Feed intakes
were higher (P < 0.01) for the ammonia—treated than for
the control silage.

In the first lactation trial. 35 lactating cows
were divided into 5 groups and fed control. urea- or
ammonia-treated corn silage for 9 weeks. Concentrate
mixtures containing 8.4. 12.9 and 18.6% crude protein
were fed at l Kg/3 Kg of milk. Milk yields. persistencies
and body weight gains for the negative control group were
lower (P < 0.05) than cows on medium and high protein
diets. Dry matter intakes were markedly improved
(P < 0.05) by either the high level of protein in the
concentrate or by the addition of urea or ammonia to the
silage. Inadequate nutrient intake contributed to the

poor performance of the negative controls. No

2

Odon P. Santana

differences were observed among silages in palatability
when dietary protein was adequate.

In the second lactation trial. three groups of
6 cows received: urea—treated silage (36%.D.M.); urea-
treated silage (52%.D.M.); or ammonia-treated silage
(42%»D.M.) as the sole forage for 7 weeks. A concentrate
mixture containing approximately 10% crude protein was
fed to all groups at the same ratio as in the first lac—
tation trial. At.the higher dry matter levels (52 to 42%).
the urea and ammonia groups performed similarly. but milk
persistencies and intakes were greater for the cows fed
36%.D.M. silage treated with urea.

There were no differences in apparent digesti-
bility of dry matter. crude protein and non-protein dry
matter due to silage treatment. Inadequate nitrogen
intake resulted in negative nitrogen balance for all
treatments. The 36%.D.M. group excreted 140% of its
digested nitrogen as milk and urine. while 113 and 106%
were obtained for the 52 and 42%.D.M. treatments. re—

spectively.

Odon P. Santana

Corn silages were treated with urea plus ammonium

polyphosphate or with ammonia at the time of ensiling

and set at temperatures ranging from 20°C to 75°C for 10
hours. Untreated and silages treated with urea at the
time of feeding were exposed to the barn conditions for
20 hours. either in the manger (fed to cows) or in open
buckets. No loss of nitrogen was noted due to heating

or exposure of the silages. The pH values increased

slightly with increasing temperature.

ANHYDROUS AMMONIA VERSUS UREA IN CORN

SILAGE FOR DAIRY ANIMALS

BY

, «(“3“
Odon Pf Santana

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Dairy

1969

@5357?

/o/22/Q7

ACKNOWLEDGEMENTS

The author wishes to express his gratitude to
his sponsor. U.S. Agency for International Development/
IRI Research Institute. Inc. and the Instituto de
Pesquisas Agronomicas of Pernambuco-—Brazi1. which pro-
vided for his stay in this country.

The author gratefully acknowledges the splendid
cooperation of his adviser. Dr. J. T. Huber. in making
this study possible.

Especially appreciated is the promptness with
which the distinguished professor. Dr. L. J. Johnson.
endeavoured to prepare the author's application materials
for admission to Michigan State University during his
advisory appointment to IRI Research Institute. Inc.
in the northeast of Brazil.

Special recognition is due to Dr. E. J. Benne
and Mrs. E. Linden. in particular. for their valuable
assistance during analyses conducted on samples related
to this work.

ii

Special thanks are also given to Mr. K. A. Wilson
for his friendly assistance during the preparation of
this manuscript.

Finally. but not least. loving thanks are due to
the author's wife. Celeste. not only for her encourage-
ment and sacrifice. but also for her remarkable confidence

and patience throughout the graduate study period.

iii

TABLE OF CONTENTS

Page
ACKNOWLEDGEMENTS. . . . . . . . . . . . . . . . . . ii
LIST OF TABLES. . . . . . . . . . . . . . . . . . . vii
INTRODUCTION. . . . . . . . . . . . . . . . . . . . 1
REVIEW OF LITERATURE. . . . . . . . . . . . . . . . 6
Use and Advantage of Silage in Cattle Feeding. . 6
Relative Feeding Value of Corn Silage for
Lactation. . . . . . . . . . . . . . . . . . . 7
Addition of Urea to Concentrate Mixtures . . . . 15

High Levels of Urea for Dairy Cows. . . . . . 22
Urea in Beef Cattle and Sheep Studies . . . . 23
Feeding Value of Urea for Growing Dairy

Cattle. . . . . . . . . . . . . . . . . . . 26
Urea Versus Biuret for Ruminants. . . . . . . 29

Ammoniation of Industrial By-Products for

Livestock. . . . . . . . . . . . . . . . . . . 32
Ammoniated Products for Dairy Cattle. . . . . 34
Ammoniated Products for Beef Cattle and

Sheep . . . . . . . . . . . . . . . . . . . 36

Resume . . . . . . . . . . . . . . . . . . . . . 41
EXPERIMENTAL PROCEDURE. . . . . . . . . . . . . . . 44
Experiment I . . . . . . . . . . . . . . . . . . 44

iv

Table of Contents.--Cont.

Addition of Anhydrous Ammonia to Green Chop

Corn. . . . . . . . . . . . . . . . . . .
Dairy Heifer Feeding Trial. . . . . . . . . .
Experiment II. . . . . . . . . . . . . . . .
Lactation Study . . . . . . . . . . . . . . .
Experiment III . . . . . . . . . . . . . . . .
Lactation Study . . . . . . . . . . . . . . .

Digestibility and Nitrogen Balance Study. . .
Experiment IV. . . . . . . . . . . . . . . . .
CHEMICAL ANALYSIS . . . . . . . . . . . . . . . . .

Dry Matter. pH. Total Kjeldahl Nitrogen. Crude
Protein Equivalent . . . . . . . . . . . . . .

RESULTS . . . . . . . . . . . . . . . . . . . . . .

Chemical Composition of Silages and Concentrates

DryMatter..................
pH. . . . . . . . . . . . . . . . . . . . . .
Crude Protein . . . . . . . . . . . . . .
Other Constituents. . . . . . . . . . . . . .
Heifer Growth Trial (Experiment I) . . . . . . .

First Lactation Study (Experiment II). . . . .
Second Lactation Study (Experiment III). . . . .

Digestibility and Nitrogen Balance Studies. .

Study on Nigrogen Losses from Corn Silages
Treated with Various NPN Sources . .

V

Page

45
45

46

47

49

SO
51

52

56

56
57
S7
57
58
58
62
62
63
67

71

76

Table of Contents.—-Cont.

Page

DISCUSSION. . . . . . . . . . . . . . . . . . . . . 80

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . 91

LITERATURE CITED. . . . . . . . . . . . . . . . . . 96

vi

Table

LIST OF TABLES

Chemical composition and pH of experimental
silages fed during the three experiments.

Formulas and chemical composition of exper-
imental concentrate mixtures used in
Experiments II and III. . . . . . . .

Intake and growth of dairy heifers fed
ammoniated corn silage. . . . . . . . .

Dry matter intakes of cows as influenced by
additions of urea and ammonia to corn
silages fed with grain at various protein
levels. . . . . . . . . . . . . . . . .

Milk and fat yields and body weight changes
of cows fed high corn silage rations
treated with urea and ammonia . . .

Dry matter intakes of cows as affected by
added ammonia and urea to corn silages
(7-week averages) . . . . . . . . . .

Milk yields and body weight changes of cows
as influenced by additions of urea and
ammonia to corn silages . . . . . . .

Dry matter intake of cows as affected by

added ammonia or urea to corn silages
(ll-week averages). . . . . . . .

vii

Page

59

61

62

64

66

68

69

70

List of Tables.--Cont.

Table

10.

11.

12.

13.

14.

Milk and fat yields and weight changes of
cows as affected by additions of urea and
ammonia to corn silages . . . . . . . . .

Fate of ingested nitrogen in cows fed
ammoniated— and urea-treated corn silages

Digestion coefficients of high corn silage
rations as influenced by addition of
ammonia and urea. . . . . . . . . . .

Fate of digested nitrogen of cows receiving
ammoniated- and urea—treated corn silages

Nitrogen and dry matter content and pH
values of urea plus AMP- and ammonia-
treated corn silages dried at various
temperatures. . . . . . . . . . . . . .

Effects of time of exposure to the environ-

mental barn conditions on nitrogen content

and pH of untreated and urea-AMP-treated
corn silages. . . . . . . . . . . . . .

viii

Page

72

73

74

75

78

79

INTRODUCTION

There is already a shortage of adequate protein
for man and for animals throughout the world and the
situation is likely to become more critical in the
years ahead.

Kolari (59) has reviewed the problem and said:
"The most serious food shortage in the future will be
protein of high quality." Undoubtedly. this will be of
major concern as the world population continues to in-
crease.

With growing competition between man and animal
for protein sources. oil meal supplementation of ruminant
rations will become increasingly less economical.

Man depends greatly on animal protein sources.
and meat and milk are essential dietary components for
many peoples.

Extensive studies had been conducted in many
parts of the world on the utilization of non-protein
nitrogen (NPN) for ruminants by the mid-1930's (8).

1

It was observed that ruminants could use simple nitro-
genous compounds through the action of the rumen micro-
organisms which form protein for the host animal. With
this foundation. there have been many studies on factors
affecting the utilization of NPN by ruminants. Specific
problems investigated have been: 1) level of NPN that
can replace natural protein without adversely affecting
animal performance; 2) palatability and ration intake;
and 3) possible side-effects due to prolonged feeding of
NPN compounds.

Urea is the main NPN compound fed commercially
to ruminants. Other simple nitrogenous compounds such
as biuret. diammonium phosphate. ammonium bisulphate
(100) and ammonium bicarbonate (33). have been suggested
as possible substitutes for natural protein in ruminant
rations. However. none except urea has made any sub—
stantial impact in the animal feeding industry.

Urea has been included as an additive to dry
grain as a part of the total nitrogen in the ration. but
decreased intakes generally resulted when urea comprised
over 2% of the concentrate (99). Perhaps a more satis-

factory method of including urea is adding it to corn

silage at ensiling time because corn silage has certain
advantages for incorporating urea into the ruminant's
diet.

Corn silage is one of the most widely accepted
feeds for dairy and beef cattle. Corn silage is indeed
the best energy crop per acre of land in many areas. A
large part of this energy is in the form of starch. which
is essential for the efficient conversion of urea to
bacterial protein (100). Corn silage has become the
principal forage for dairy cattle in many parts of the
USA. This feedstuff is higher in available energy and
lower in crude protein. compared to legume forages.

Urea added to corn silage at the time of ensiling
is partially broken down to ammonia and this ammonia has
an important role in the fermentation process. Ammonia
increases the corn silage pH and tends to lengthen the
fermentation time. A significant increase in organic
acid concentrations. primarily ammonium lactate (46. 88).
also results from treating corn silage with urea.

The optimum amount of urea that should be added
to corn silage for best results is still questionable.

However. 0.5 to 0.75%»has given good results.

This study was a comparative evaluation of corn
silages treated with anhydrous ammonia or urea.

Anhydrous ammonia is a volatile alkaline gas (NH3)
extremely soluble in water. It combines with acids to
form a number of salts. Ammonia is the principal source
of fixed nitrogen used in the manufacture of fertilizers
(82% nitrogen) .

Douglas g£_al. (27) stated that the ammonia pro-
duction in the USA for the fiscal year 1963-1964 was 5.8
million tons and that about 74% of this production was
utilized as fertilizer. thus. the importance of ammonia
for agricultural applications is obvious.

In the March. 1969 edition of Oil Plant and Drug
Reporter (75). prices for feed grade urea (45%.nitrogen)
ranged from $84 to $88 per ton and $50 to $92 per ton for
anhydrous ammonia (82%.nitrogen). Most recent comparisons
have shown that the price of anhydrous ammonia is usually
lower than that of urea. This cost advantage is further
magnified by the fact that anhydrous ammonia contains 82%
nitrogen compared to 45% for feed grade urea.

Methods for including anhydrous ammonia in animal

feeds are more complicated than for urea (32). This is

because the ammonia is available as a liquefied gas main—
tained under high pressures.

To date. very little research has been reported
on adding anhydrous ammonia to corn silage. It would
seem that silage should serve as a desirable vehicle for
carrying the ammonia because of its acid nature which
would enhance formation of ammonium salts and prevent

volatilization of the gas.

REVIEW OF LITERATURE

Use and Advantage of Silage
in Cattle Feeding

The history of the feeding of the silage dates
back to antiquity. The silo has been used for many
years to assure a satisfactory conservation of crops.
Miles (68) in 1889 reported that "The preservation of
green fodder for winter feeding has for many years en-
gaged the attention of practical men as a matter of
great economic interest . . . . ." As early as 1895
W011 (110) stated that: "A German agricultural writer
predicted the day as likely to come when dry hay would
only be obtainable in drug stores."

Corn silage has merits not commonly observed in
most dry roughages. It is a low cost feed. of high
palatability and usually yields more energy per acre than
other crop alternatives (23. 73). especially when hare
vested in the hard dough (32—37% dry matter) stage where
maximum yields are obtained (43).

6

Relative Feeding Value of Corn Silage
for Lactation

Numerous reports (2. 30. 104. 105. 106. 107) have
discussed the use of corn silage for dairy cows. Carroll
(17) showed a higher milk and fat production of cows on
the corn silage ration than those which received hay and
additional grain. A sudden increase in milk yield was
observed by Bartlett (2) when a dairy cow ration consist-
ing of hay and a mixture of cottonseed meal. bran and
corn meal was partially replaced with corn silage for
about two months. A significant decrease in production
was observed when the additional silage was taken from
the ration.

An early report by Williams (109) claimed that
35 pounds of low-quality corn silage could replace 10
pounds of alfalfa hay in the dairy ration. Another study
by Bechdel (5) demonstrated that corn silage was superior
to silage made of Canada field peas and oats.

Corn silage has also been shown to be equal or
superior for dairy cows to alfalfa-brome grass silage

(103); sunchoke silage (26); and meadow crop silage (72).

In more recent reports (14. 60. 76) corn silage was shown
superior to sorghum silages.

Feeding of corn silage as the sole roughage has
been suggested by some research workers. Good results
were found by the Ohio Experiment Station (71) when cows
were fed corn silage continuously during a period of
approximately 5 months. The cows maintained normal milk
and butterfat production with good health and satisfac-
tory body weight gain. Porter (81) paired 22 Holstein
heifer calves at birth. One calf of each pair was fed
corn silage as the only roughage. and the other calves
were initially fed hay for about 6 months and then both
hay and silage. subsequently. No appreciable differences
between groups were shown for breeding efficiency or milk
and butterfat production. Records for the first and
second lactations indicated that the milk and fat yields
for the corn silage and the hay plus silage treatments
were 12.876. 422; 14.369. 471; and 11.511. 399; 12.567.
421 pounds. respectively. In a later study Converse (22)
reported that dairy cows receiving only corn silage and
concentrates maintained about the same level of produc-
tion as those cows fed corn silage. hay and concentrates

when the total levels of nutrients were the same.

A progress report was conducted at the Connecticut
Experiment Station by Pratt and White (82) comparing light
or heavy amounts of silage in dairy rations. The results
indicated that high silage ration resulted in slightly
greater dry matter consumption and milk production.

Huffman and Duncan (48) fed one group of cows on
all-hay and another group on hay-corn silage rations.
They reported that when part of the total digestibie
nutrients (TDN) of an all-hay ration was replaced by an
equal amount of TDN from the silage. an increase in Fat-
Corrected Milk (FCM) occurred in 22 of 23 trials. The
valuable quality of the TDN in the corn silage was
attributed to the presence of an unidentified grain
factor(s) in the corn which was needed to balance the
TDN in the roughage diet.

Corn silage and recombined corn silage were
studied by Dunn g£_gl, (28). The amount of corn and cob
meal fed in the recombined corn silage was equivalent to
the amount of corn in the normal corn silage. No sig-
nificant differences were observed in FCM production.
body weight gains. and amount of digestible protein in-

gested during the feeding periods. The authors concluded

10

that the grain in corn silage was of the same nutritive
value as dry corn and cob meal.

Some studies have suggested that forages other
than corn silage are more valuable as a roughage for milk
production. Hinton.§£;§l, (38) treated first-cut alfalfa
and Lespedeza sericea silages with a molasses-phosphoric
acid mixture and compared their feeding value with corn
silage. Twelve lactating cows were divided into three
groups which received twenty pounds of silage each.

Ground alfalfa hay was offered ad libitum and 10 pounds

 

of a grain mixture. The results. over a period of 120
days. showed that the body weight and production of all
groups were normal. but a higher production of alfalfa
silage than of the corn silage groups was observed. In
Mississippi (12) corn silage was compared with silages
from NK 300 (an intermediate forage-type grain sorghum)
and with RS 610 (a combined grain sorghum). All cows
recieved silage ad libitum and 0.5 pounds of alfalfa hay
per 100 pound body weight daily. A grain mixture with
15.5% crude protein was also fed according to NRC
standards. The average persistency of production was

80.5. 78.0 and 117.5%Ifor the respective treatments.

11

Corn silage was compared with oats and vetch and sunflower
silages (51). Three trials were conducted at the Oregon
Experiment Station which involved 32 dairy animals. The
results favored oats and vetch silage as producing the
largest amount of milk with the corn and sunflower silage
following in that order. Another experiment was conducted
by Jones and Brandt (50) comparing the feeding value of
kale and corn silage. In three of the four trials. kale
feeding resulted in slightly higher milk yields. but a
slightly lower butterfat production. Nevertheless. a
higher body weight gain was observed in three of the four
trials by the cows fed corn silage.

In Utah (4). wet beet pulp was compared to corn
silage for four consecutive winter feeding periods.
Twenty-two Holstein cows were divided into two groups.

One group was fed 57.5 pounds of corn silage and the

other 93.8 pounds of beet pulp. The average dry matter
content of the corn silage and beet pulp were 26 and 11.5%,
respectively. The daily production per cow during the

four winter periods averaged 23.5 pounds milk. with 0.77
pounds of butterfat for the corn silage cows. and 27.9

pounds of milk containing 0.91 pounds butterfat for the

pulp group.

12

The unfavorable results obtained with corn silage
as the main forage for milk production may be attributed
to several factors. These are: ecological conditions.
quality and dry matter content of the silage. amount and
quality of supplemental concentrate and mineral supplemen-
tation.

Despite the conclusions that. under certain con-
ditions. corn silage may not be more valuable than some
other roughages for cattle feeding. one cannot deny the
importance that corn silage plays in the feeding of
ruminants. This is justified by the rapid and tremendous
adOption of corn silage in the ration of dairy cows.

In 1952. Converse and Wiseman (22) stated that
the amount of silage made in this country primarily from
corn and sorghum had increased to an estimated 40 million
tons annually. In a more recent report. Hoglund (39)
concluded that from 1960 to 1965 corn silage acreage per
farm in Southern Michigan increased by 50 and 20%.for
the farms with less than 50 and with 50 or more cows.
respectively. In an excellent review on corn silage in
the ration of dairy cattle. Coppock and Stone (23) stated

that there has been a marked increase of the number of

13

hectares of corn harvested as corn silage in the United
States during the last two decades. But in contrast to
this. about a 25% decrease has been observed in the number
of hectares harvested as corn grain.

Many comparative feeding trials (23) with corn
silage have shown the merit of this forage as a source
of energy for cattle; especially when made from the well
matured corn plant. which is equal to the best forages
or combinations of forages.

The corn plant is relatively low in crude protein.
Various approaches have been tried to increase its nitro-
gen content. In 1944. Woodward and Shepherd (111) studied
the feeding value of corn silage treated with 0.5% urea.
This silage was fed with a low—protein concentrate and
hay to a group of lactating cows. Another group received
an identical treatment. except that the urea was mixed
with the concentrate. Both treatments maintained compar-
able milk production. In Michigan. Huber g£_§l. (46)
fed corn silages ad libitum to 54 lactating cows for an
80-day feeding period. The corn was cut at different
maturities and contained 30. 36. and 44%,dry matter.

The silages were treated with urea (0 or 0.5%) at the

14

time of ensiling and fed to nine groups of six cows each.
Untreated silage was fed to six groups. three of which
were fed a 13.8% crude protein concentrate while the
other three received an 18.7% mix. The groups fed urea-
treated silage received the 13.8%.concentrate. At the
two earlier maturities. the urea silage did not affect
the milk production but a decrease occurred when urea

was added to 44% dry matter silage resulting in a signif-
icant interaction between urea-treatment and silage
maturity.

In a two-year study conducted by Polan g£_§l. (79)
corn silages were fed as the sole forage to dairy cows.
For the first year silages were treated with 0. 0.5 and
0.75% urea. while levels added during the second year
were 0. 0.5 and 0.85%. It was calculated that the high
urea treatments furnished 27 and 38%.of the ration
nitrogen during the successive years. Treatments lasted
70 and 63 days. respectively. The rations were approx-
imately isocaloric and isonitrogenous. Milk yields during
the treatment periods averaged 20-25 kg. daily. No sig-
nificant depressions in production or feed consumption

resulted from urea-treatment of silages. A nitrogen

15

balance trail conducted during the second year of the
study showed that the nitrogen excretion exceeded the

intake at the highest urea level.

Addition of Urea to Concentrate Mixtures

Ward et al. (102) compared the milk-producing
value of a low-protein roughage supplemented with two
experimental mixtures. These were corn with 2% urea and
soy bean oil meal. Under the conditions of this exper-
iment. urea plus corn and soy bean oil meal were con-
sidered to be of similar feeding value. since maintenance
of body weight and milk production did not show any sig-
nificant differences. At the Virginia Station (94).
during a 3—year period. three trials were conducted in-
volving 3 groups of 4 cows each. Hay. corn stover and
corn silage were the roughages fed in Trial 1. In Trials
II and III no stover was included. The concentrates con-
tained corn and cob meal. ground oats. bone meal and
salt. The authors concluded that urea plus corn and

cottonseed meal were of similar value for milk production.

16

They also noted that the addition of corn cobs did not
alter milk production or digestibility.

An outstanding herd was used for a feeding test
in 1944 (34). Seven cows of this herd were selected as
the experimental group to be compared with 15 other rep-
resentative cows as the control group. Alfalfa hay and
corn silage were fed with one of two concentrates of
20.6%.crude protein content. Concentrate fed the control
group contained a small amount of urea. while sufficient
urea was added to the test concentrate to equal as much
as 43% of the total ration nitrogen. The results obtained
over a 210-day period indicated that milk production was
about the same for test and control concentrates. so the
author concluded that urea was effectively used. However.
it is doubtful that dietary protein was low enough ini-
tially to evaluate the benefit of the added urea.

In Virginia. Huber gt_gl, (42) conducted two
trials with 40 lactating Holstein cows for 12 weeks.

All groups received corn silage ad libitum as the only
forage. The forage was supplemented on an equal nitrogen
basis. with the following: 1) a concentrate mixture with

15% crude protein fed at 1 pound per 3.5 pounds of milk;

17

2) soybean or cottonseed meal; 3) oil meal plus urea
(each furnished equal nitrogen); and 4) urea. In the
first trial. the silage dry matter intake for these four
groups were: 1.78. 2.31; 2.30 and 2.30%.of body weight.
respectively. The milk yields for the respective treat-
ments were: 51.3, 48.7. 43.6 and 36.0 pounds per day.
The persistency of production (as a percent of the
standardization period) followed a trend similar to milk
yields. In Trial II the group supplemented with only
urea was significantly lower in milk yields and dry matter
intake than the other three groups. Little difference
in performance was noted between groups 1. 2 and 3.
The reason for the different results between the two
trials was probably because production levels were lower
and cows were later in lactation in Trial II than I.
This study showed very clearly that milk yields could not
be maintained~with only corn silage and urea. but con-
clusions concerning the replacement value of urea for
natural protein would be biased because the rations were
not balanced for their energy content.

In another report. Virginia researchers (45)

added varying amounts of urea at the time of feeding to

18

rations for high producing dairy cows. Ninety—one lactat-
ing cows were involved in three experiments. Corn silage
was fed ad libitum as the sole forage. Urea supplied
from 0 to 48% of the total dietary nitrogen. No adverse
effect on milk production was observed when 11% of the
nitrogen came from urea. However. when urea furnished

21 to 23%. milk yields were significantly decreased. A
more radical depression in milk production was noted when
urea supplied 38 and 48%,of the ration nitrogen. Corn
silage intake was not decreased by the addition of urea.
but the silage consumption was depressed on high-
concentrate rations containing urea. From these studies
the authors concluded that the maximum urea that can be
added to concentrate for high producing cows without de-
pressing milk yields is about 180 g/day. They further
suggested that the old recommendation of furnishing about
1/3 of the dietary nitrogen as urea is not applicable to
cows at high production levels where protein needs are
greatly increased. Holter and co-workers (40) reported
that no significant differences in dry matter intake and
ration utilization resulted from the addition of 1.25.

2.0 and 2.5%.urea to concentrate for dairy cows on

19

isonitrogenous rations with corn silage as the only
forage. However. nitrogen retention was significantly
depressed by the addition of urea to the concentrate
mixtures.

In a field study reported by New Hampshire
workers (41) fifty-six high-producing cows were allotted
to two groups and individually fed hay and corn silage
ad libitum. A premium commercial concentrate was fed
to one group during the testing period. The other group
received a similar concentrate in which corn and 1.5%
urea replaced part of the oil meal on an isonitrogenous
basis. The maximum urea intake was 0.17 kg. daily.

Milk and butterfat production for urea and non-urea
groups were: 8.028. 299 and 8.059. 308 kg.. respectively.
The urea level fed to the cows in this study appeared to
be acceptable even to cows producing up to 30 kg. milk
daily.

Van Horn gg_gl. (99) reported that addition of
2.2 and 2.7% urea to concentrate mixtures reduced concen-
trate intake significantly. Milk yields were less from
cows on urea treatments. which suggested that milk pro—

duction was directly affected by the amount of concentrate

20

eaten. In another experiment the cows were allotted to
three groups. Group 1 was the control. and groups 2 and
3 received urea—treated corn silage (5.0 kg. of urea per
metric ton at the ensiling time). The third group was
fed a concentrate with 1% urea added. All groups were
offered 27 kg. silage and about 3.0 kg. alfalfa hay daily.
No significant differences in milk yields and feed intake
were noted between the treatments.

Colovos g£_gl. (19. 20) reported the results of
two experiments showing the effects of different levels
(0. 1.25. 2.0. and 2.5%) of urea (42% nitrogen) in con-
centrate mixtures. In the first experiment. the concen-
trate fiber levels were 5 and 8%“ Fair quality timothy
hay was offered as the sole forage at 2% of body weight.
In the second experiment concentrates averaged 6.64%.fiber
and good quality timothy hay'were.fedras described pre-
viously. The authors concluded that urea in concentrates
did not significantly affect ration intake and milk pro-
duction. Digestibility of fiber was significantly in-
creased by urea when added to low fiber concentrate.
However. an adverse effect resulted from the addition of

urea to the high fiber concentrate. In another study.

21

urea was compared to linseed oil meal for milk production
(86). Corn silage and timothy hay comprised the rough-
ages. A basal concentrate mixture containing about 10%
protein was treated with urea or linseed meal. Urea
nitrogen constituted 27%.of the total nitrogen in the
ration. Data on milk production did not indicate signif-
icant differences among treatments.

Reid (84) reviewed the use of urea as a protein
supplement and stated that urea could effectively sub-
stitute for plant protein when fed at levels of not more
than 27%.of the total ration nitrogen. The use of urea
and other non-protein nitrogen compounds was reviewed by
Stangel (91). He listed more than 1500 citations. Nu—
merous experiments summarized by Stangel suggested that
urea was successfully used as a nitrogen extender when
the urea—nitrogen did not furnish more than one—third of
the proteinvequivalent in ruminant rations. However.
recent data show that this may not be true for high pro-
ducing cows. particularly when the urea is fed through

the concentrate.

22

High Levels of Urea
‘£g£_2airy Cows

Early work at the Hawaii Agricultural Experiment
Station (108) suggested that urea can function as a
source of nitrogen for ruminants but not as efficiently
as nitrogen of plant origin. Depressions in milk yields
were observed when either 19 or 36% of the total crude
protein equivalent was furnished by urea.

Conrad and Hibbs (21) fed corn silage containing
0.T% urea as the only feed for milking cows in late lac—
tation. but results were inferior to a conventional a1-
falfa hay-grain ration.

Lactating cows were fed silages treated with 0.5
and 0.75% urea. or 1% diammonium phosphate (90). Nitro-
genous additives did not significantly affect milk pro-
duction but lower intakes were noted for cows fed silages
containing 0.75%.urea or 1% diammonium phosphate.

As already mentioned. promising results were ob-
served by Polan gt_§l. (79) when 0.85% urea was added to
corn material at the ensiling time which furnished 38%
of the dietary nitrogen; but marked depressions in milk

production were reported by Huber et al. (45) when 38 to

23

48% of the ration nitrogen was supplied by urea. A
comparison of these studies indicates that treating corn
silage with urea allows for intake of higher urea levels
without depressing milk yields compared to the conven-
tional method of adding all the dietary urea to the con-

centrate;

Urea in Beef Cattle and
Sheep Studies

Cullison (24) added 10 pounds of urea per ton to
sweet sorghum silage for beef cows. The group fed urea-
treated silage maintained body weight during the.feeding
period. while the negative control group lost an average
47 pounds per head. Urea addition also made the sorghum
silage more palatable and higher in carotene content.

Blaylock.gg_gl. (7) fed 0. 23. 45. 68. 91. 113.
136. 159 and 181 gm. urea per steer daily for a 112—day
feeding period to 108 steers (9 per treatment). Animals
were fed ground ear corn ES libitum and 907 g. hay/day
in addition to a protein supplement which contained 32

to 62% crude protein equivalent. Daily gains did not

24

significantly differ between treatments and averaged
1.21. 1.25. 1.37. 1.29. 1.32. 1.37. 1.39. 1.34 and 1.34
kg.. respectively.

In 1947. Briggs g£_§l, (9) studied the value of
urea as an extender of protein for beef cattle. Crystal-
line urea and pelleted feeds containing urea were used
in the digestion trials and feeding experiments. The
nitrogen furnished by urea in the different supplements
varied from 25 to nearly 100%.of the total in the various
rations. Low grade prairie hay as the basal ration was
fed to appetite along with the supplements. Pellets con-
taining not more than 50% urea nitrogen were comparable
to cottonseed meal in providing the nitrogen storage.
Urea alone was considered a poor supplement to prairie
hay. In this study urea was fed at relatively high levels
but toxic effects were observed.

Perry.g£_§l. (78) compared the feeding value of
urea supplements to those of natural protein in seven
different trials. In six of these trials the cattle
received a 64% crude protein supplement and for the
seventh trial. supplements of 80 and 96% crude protein

were fed. Urea content of the supplements was 21-22. 28

25

and 35%w respectively. High moisture ground ear corn
and a limited amount of corn silage were fed in the
fattening rations. For the growing rations. corn stover
silage or corn silage plus the experimental supplements
were fed. Growth on the natural protein rations was not
significantly different from those containing urea. In
one fattening trial. however. the natural protein group
was significantly higher than the higher urea group.
Lowrey and McCormick (62) recently showed that
steers and yearling calves could utilize concentrate ra-
tions when most of the supplemental nitrogen came from
urea. However. the body weight gains in yearlings
averaged somewhat less on all high-urea treatments. At
high urea levels. nitrogen digestibility was higher and
feed intakes lower for both the yearlings and steers.
Raleigh and Wallace (83) used 30 Hereford steer
calves in an attempt to establish an adequate level of
protein supplementation for meadow-hay (5.5% crude pro-
tein). Nitrogen supplements compared were urea. cotton—
seed meal or a mixture of both urea and cottonseed meal.
Salt and monosodium phosphate were added at 1% and chromic

oxide (as an indicator) at 0.5%.of the total diet. The

26

hay was mixed with the other ration components and
pelleted. The percent urea in the experimental diets
ranged from 0 to 2.52. Urea and/or cottonseed meal
raised the crude protein levels of rations from 5.5 to
6.0; 9.0 and 12.0%“ Data on gains. feed intake and
feed efficiency were significantly higher at 9 and 12%
crude protein levels than 6%»or hay alone. Nitrogen
source has a significant effect on gains with better
performance on the plant protein than on the plant pro-
tein plus urea or the urea alone. Urea was inferior to
plant protein at both 9 and 12%.protein diets. Toxicity

was noted at the highest level of urea.

Feeding Value of Urea for
Growing Dairy Cattlg

Bartlett and Cotton (3) reported satisfactory
results over a 142—day feeding period with 21 dairy
heifers when 0.127 pounds of urea was added to low-
protein rations.

Hart‘gg_gl. (33) reported that growing calves

(250-290 pounds) fed rations in which urea supplied 43%

27

of the nitrogen had slightly less growth than calves fed
66%.of the ration nitrogen as casein. Data reported in
this experiment also indicated that nitrogen not only

from urea. but also that furnished by ammonium bicarbonate
was utilized by calves.

Lassiter §£_gl, (61) fed ground corn cobs as the
only roughage to 24 growing dairy heifers in a 150-day
trial. Three experimental mixtures were offered in which
30. 50 and 70%.of the ration nitrogen came from urea.
Daily gains were significantly depressed as urea nitrogen
increased. Brown 2E_El- (10) showed that dairy calves
fed an experimental starter (15.1% protein equivalent)
with 54.2% of the nitrogen as urea grew at about the same
rate as those fed a natural protein supplement (15.2% pro-
tein). These two groups were significantly superior to
a third group fed a low protein diet (6.7% protein). The
data showed that 6-7 week old calves could utilize urea
as a nitrogen source.

The frequency of feeding seems to affect urea
utilization. A study by Campbell 35*31. (16) showed
similar growth results when they fed conventional protein

and urea nitrogen to dairy heifers six times daily. but

28

gain was significantly reduced when the urea-supplemented
group was fed only twice a day.

Antibiotics such as chlortetracycline have been
used to promote the utilization of urea by young dairy
calves. In a Kentucky study (11). urea was fed at 30.8.
46.3 and 57.5% of the ration nitrogen. Crude protein
equivalent in these diets ranged from 6.5 to 15.3%. The
urea-supplemented animals fed the 12.1%.crude protein
equivalent ration with chlortetracycline gained signif-
icantly more than those on the 6.5 or 9.4%.rations. The
authors suggested that as early as 3 weeks of age some
urea nitrogen was utilized by the young calves.

The Ohio workers (6) added 17. 20. and 25 pounds
of urea per ton to chopped corn at the ensiling time and
noted that a large part of the added urea was hydrolyzed
to ammonia during the ensiling process. In fact. most
of the added urea nitrogen was retained as ammonium salts
of organic acids. In digestion trials with sheep. it
was observed that the urea nitrogen was utilized as
efficiently as the nitrogen supplied from soybean meal.
The palatability and feeding value of the urea-treated

silage were studied in three cattle-feeding experiments.

29

Results of two trials with a limited number of steers
showed the treated silage to be a safe and palatable
feed. The third experiment indicated the feeding value
of the urea—treated corn silage was comparable to that

of corn silage and soybean oil meal.

Urea Versus Biuret for
Ruminants

Excessive ammonia nitrogen from urea or ammonia
salts is easily wasted by the animal. Other non-protein
nitrogenous compounds. such as biuret. may be less toxic
than urea and could have economic importance as a nitrogen
source for ruminants.

Several studies have investigated biuret as a
non-protein nitrogen addition for ruminant animals (29.
35. 49. 66).

Meiske.et a1. (67) added either urea. biuret.
crude biuret or soybean meal to a basal ration contain-
ing 7.13% crude protein for 50 fattening lambs. The
crude protein levels of the lamb rations after the NPN

additions were: 9.11. 9.08. 9.10 and 9.69%. respectively.

30

Feed efficiency and body weight gains were markedly in-
creased by the added nitrogen regardless of source.

Urea and biuret were compared as a nitrogen
source in a series of experiments by Karr gt_§l. (52).
Results from two of the three metabolism trials indicated
that biuret significantly improved nitrogen retention
when added to basal corn silage which was fed to fatten-
ing lambs. Nitrogen retentions were consistently lower
in the urea than the biuret fed groups. A 26% increase
in gains resulted from addition of urea or biuret to the
basal diet.

In South Africa. Clark §E_gl, (18) showed that
biuret was more satisfactory than urea as a nitrogen
supplement for sheep fed high fiber. low protein rough-
ages. Such results should be expected from adding biuret
to a high fiber ration because of its slower rate of
hydrolysis and lack of effect on palatability.

Studies by Hatfield g£_gl. (35) compared biuret
and urea in metabolism. toxicity. growth and reproduc-
tion tests with sheep and beef cattle. and showed that
biuret could safely supply a large portion of the nitrogen

required by those ruminants. One report has indicated.

31

however. contradictory results on the feeding value of
biuret. Schaadt EE_E£- (89) reported lower gains and a
failure of sheep to readily adapt to biuret-containing
rations. They also suggested that the main site of
biuret hydrolysis and metabolism was probably not within
the rumen. but in other tissues of the animal.

There are only a limited number of trials on
biuret in milking cows. In 1968 two experiments were
conducted in Scotland by Waite g£_gl. (101) involving
39 cows to compare the feeding value of biuret and urea
as a total substitute for the nitrogen supplied by the
oil cake in concentrates. Urea and biuret replaced 52
and 43%»of the total nitrogen in the concentrate mixtures
used in the first and second experiments. respectively.
Good quality hay was fed as the only roughage. No dif-
ferences in milk yields between biuret and urea treat-
ments were noted. However. production by the urea- and
biuret- supplemented groups was lower (10%) than that of

the control treatment.

32

Ammoniation of Industrial Berroducts
for Livestock

Many industrial by-products have long been util-
ized as livestock feeds. Cane molasses. condensed dis-
tillers molasses solubles. blackstrap molasses. citrus
pulp. sugar beet pulp. are some common by-products used
in ruminant rations.

In general. most of these feeds are low in pro-
tein. so attempts have been made to increase their
nitrogen content.

A considerable number of reports in the litera-
ture (25. 55. 57. 63. 64. 65. 70) have demonstrated that
after ammoniation these materials might serve as sources
of nitrogen for ruminants.

In 1941. Millar (69) treated air-dry sugar beet
pulp with anhydrous ammonia resulting in the fixation of
ammonia nitrogen. An increase of 2.4% nitrogen occurred
without external heat. or prolonged ammoniation. How-
ever. to secure a product having a higher percentage of

ammonia nitrogen. increases of temperature. pressure. and

time of ammoniation were required. Under a pressure above

1000 pounds per square inch. at 232°C for two hours.

33

nitrogen content of the beet pulp was raised from 1.6%
(in the original material) to over 10%. The feed color
became progressively darker with increased ammoniation
temperatures. The major part of the nitrogen fixed at
increased temperatures was water-insoluble. However.
when the ammoniation was accomplished without external
heat and at low pressures. 96.44% of the added nitrogen
was water-soluble.

A small portion of corn silage was also ammoni-
ated under conditions similar to those used for beet
pulp. This study represents one of the few references
found on ammoniation of corn silage in the literature.
No nitrogen losses were detected from ammoniated silage
samples stored for 5 months.

Intakes by sheep and dairy cattle decreased as
ammonia content of the beet pulp or corn silage increased.
In case of the pulp. the author suggested for a suitable
protein supplement the nitrogen content should be limited
to 6%.

An increase of about 1.5% nitrogen was obtained
when corn silage (67% moisture) was ammoniated at low

pressure. Higher pressure (155 psi) and temperature

34

(108°C) were required for an increase of 2.0% nitrogen.
The physical appearance. odor and palatability of the,
silage so ammoniated were considered undesirable.

Stiles (93) also ammoniated forage-type materials
with the objective of fixing the ammonia nitrogen through
chemical combinations that release in the rumen at a

rate adequate for microbial protein synthesis.

Ammoniated Products for
Dairy Cattle

In Pennsylvania. Knodt et a1. (56) conducted a
series of growth studies in which ammoniated cane molasses.
ammoniated inverted cane molasses and ammoniated con-
densed distillers molasses solubles replaced soybean meal
and oats nitrogen in rations for dairy calves. They
demonstrated that when the ammoniated products were fed
to calves over 12 weeks of age. gains of nearly 2.0
pounds daily were obtained. However. younger calves did
not grow well on the ammonia nitrogen.

Ammoniated cane molasses and urea were fed to
dairy heifers as replacements for the nitrogen of cotton-

seed meal by the Louisiana workers (77). The concentrate

35

mixtures used contained 12.4. 12.6 and 13.1% crude pro-
tein. Urea and ammonia replaced 30% of the protein
equivalent in the experimental rations. Daily gains
averaged 1.23. 0.92 and 1.04 pounds for cottonseed meal.
urea and ammoniated molasses treatments. respectively.
The ammoniated molasses was quite palatable in this
feeding trial. The highest intake per pound of gain was
required by the urea-supplemented animals.

Magruder gt_§l, (63) reported that ammoniated
cane molasses fed to milking cows at 10% of the grain
ration was well utilized for milk production and body
weight gains. These researchers also fed ammoniated wood
molasses (Masonex) to growing dairy heifers at 10% of
the total ration and obtained favorable results.

Ammoniated citrus pulp was fed to dairy cattle
as a carbohydrate and crude protein supplement (25).
Satisfactory results were reported when 30 to 40% of the
total digestible nutrients. and 15 to 20% of the ration
nitrogen was supplied by the ammoniated citrus pulp.

Inverted cane molasses which had been highly
ammoniated (38% crude protein equivalent) was fed at 10%

of the grain ration containing 18% protein as a cottonseed

36

meal substitute (87). Satisfactory growth was made by
the dairy steers on the experimental ration. However.

the treated molasses when fed ad libitum. along with hay

 

and grain. was not palatable. This lack of palatability
was attributed to the high alkalinity (pH 8.5) of the

feed.

-Ammoniated Products for
Beef Cattle and Sheep

Several ammoniated by-products have been eval-
uated in fattening and wintering rations for beef cattle.
In 1951. Tillman and Kidwell (95) reported the value of
ammoniated condensed distillers molasses solubles as a
protein source and carbohydrate extender. Gains were
comparable for all groups. but slightly lower for the
lots fed the highest level of ammoniated material.

Four experiments were conducted by McCall and
Graham (65) comparing ammoniated cane molasses. ammon-
iated citrus pulp and furameal with natural proteins.
The study involved 251 fattening steers. The protein

equivalent levels were 24% for the ammoniated molasses

37

and ammoniated citrus pulp; and 35%.for the furameal.
Steers fed a protein supplement in which furameal
supplied about one-fifth of the nitrogen gained slightly
more than those on the diet in which urea replaced a
similar amount of protein. When ammoniated molasses re-
placed one-sixth of the protein in the supplement gains
were exactly the same as the control. but slightly less
when fed to replace one-fifth of the supplemental protein.
Furameal and ammoniated molasses were combined with each
supplying one-fifth of the supplemental protein. The
ration produced slightly higher gains than the control
with about the same feed efficiency. The ammoniated
citrus pulp diet gave gains comparable to the controls.
with about the same feed consumption. The authors con-
cluded that the ammoniated products were satisfactory
protein substitutes for fattening steers when fed to the
level of 40%.of the protein supplement.

In Florida. Kirk g£_gl. (53) measured the nutri—
tional value of ammoniated citrus pulp in fattening
rations. Pangola-grass hay. cottonseed meal. plain
citrus pulp. and citrus molasses were used in the feeding

trials. Ammoniated citrus pulp containing 12.9% crude

38

protein equivalent. replaced most of the plain pulp and
part of the cottonseed meal. Average daily gains by
cattle fed ammoniated citrus pulp was lower than that of
the control lots. The workers suggested that a lack of
palatability of the experimental rations would explain
the low gains.

In Oklahoma. Pope gE_§l. (80) found that ammon-
iated cane molasses (17%Icrude protein equivalent) suc-
cessfully replaced one—third of the cottonseed meal on
a protein equivalent basis in wintering beef cows. Cows
fed a combination cottonseed meal and ammoniated molasses
gained significantly more than those fed cottonseed meal
alone.

Nine trials on ammoniated cane molasses (16 to
33%.crude protein equivalent) and ammoniated furfural
residue (34.4% crude protein equivalent) were reported
by Tillman g£_gl. (97). The results generally indicated
that the ammonia nitrogen in these products was not well
utilized. Ammonia treated molasses gave results compar-
able to urea only in the wintering trials. An unusual
behavior was observed among steers fed 2 pounds daily of

high-ammoniated cane molasses (32.2%.protein equivalent).

39

This was characterized by short periods of violence.
running into or jumping fences in a highly excited
manner.

In digestion and nitrogen balance studies with
sheep. Tillman and Swift (96) found that ammoniated
cane molasses (ACM) was inferior to both soybean oil
meal and urea when these supplements furnished 17% of
the total ration nitrogen. But with respect to palata-
bility. the trial showed that both ammoniated condensed
distillers molasses solubles and ammoniated cane molasses
(ACM) were acceptable to animals when fed at 10%.of the
total ration. In a more recent report. Tillman gg_gl.
(98) added a high-ammoniated cane molasses to low and
medium protein control diets in order to supply 49 and
38% of the total ration nitrogen. Nitrogen digestibility
(calculated by difference) was 50 and 42% for the respec-
tive rations. In a fattening ration. ACM gave unfavor-
able results and sheep on the supplemented rations pre-
sented endocardial hemmorhage condition.

Hershberger g£_gl. (37) and Ferguson and Neave

(31) have also reported unimpressive or negative results

40

from digestion and nitrogen balance trials with sheep
fed ammoniated by—products.

Other investigators have also reported unusual
behavior in cattle fed ACM (1. 85). Sheep fed a high
level of ACM exhibited mild to extreme excitement (98).
Because of these pathological signs. Tillman g£_gl. (97)

stated:

Apparently the stimulatory agent is concen-
trated to a greater extent in the ammoniated
high-test molasses product than in the ammon-
iated cane molasses (16 and 38%). Because of
.their violent response. animals stimulated by
these products may not only injure themselves.
but also become a hazard to personnel.

Resume

The excellent quality of corn silage as a source
of energy for dairy cattle has been substantiated by
many feeding trials. Corn silage when adequately pre-
pared is one of the most productive forages from both .
an acreage yield and total digestible nutrients stand—
point. However. because of the relatively low crude
protein content of corn silage it should be supplemented
with a satisfactory source of nitrogen. Urea treated
corn silage as the only forage for lactating dairy cows
has been successfully reported by several investigators.

Studies have demonstrated good performance in
lactating cows fed corn silage treated with 10 to 17
pounds per ton of urea at ensiling time. Nutrient diges—
tibilities and nitrogen retention of low-protein basal
rations are increased by the addition of urea. Urea
treatment at ensiling time lengthens fermentation time
and increases organic acid concentration in silages.

Urea added to concentrate at 2%.has been shown

to decrease palatability of rations. Milk production in

41

42

high-producing cows was depressed when 21 to 25%.of the
total ration nitrogen was supplied by urea in the concen-
trate. Marked decreases in milk yields resulted when
urea in the concentrate furnished 38% of the total ration
nitrogen. Urea fed at very high levels has been fatal
even for adapted animals. However. much lower intakes
are toxic to unadapted animals.

Calves can utilize urea as early as 6 weeks of
age. In some studies. urea-supplemented calves grew at
comparable rates to conventional-protein groups.

Biuret. another NPN compound. was found to be
comparable to urea as a nitrogen source for ruminants.
Biuret can safely supply a considerable quantity of the
nitrogen required by sheep and cattle. Biuret appears
to be less toxic and more palatable than urea in the
diet of ruminants. However. its use in milking rations
in the U.S.A. is presently forbidden because of its
appearance in milk of cows fed the compound.

Many industrial by-products have been used as
livestock feeds. Several research reports have shown
that the low crude protein content of these products

may be considerably increased by addition of urea or

43

anhydrous ammonia. Ammoniation of these feeds can be
accomplished in an economical and practical way at room
temperature. Higher ammonia nitrogen fixation is pos-
sible under high pressure and high temperature. Palata—
bility of ammoniated feed for sheep and cattle is de-
creased as feed undergoes higher pressures and higher
temperatures for nitrogen fixation. Ammonia nitrogen
fed to calves over 12 weeks of age was satisfactorily
utilized. Dairy heifers on ammoniated rations gained
slightly better than those on a urea diet. Dairy cows
fed ammoniated cane molasses at 10% of the grain re-
sponded favorably in milk production and body weight
gains. Ammoniated products added to fattening and
wintering-type rations gave satisfactory results when
compared to the conventional rations. Abnormal behavior
was observed in cattle and sheep fed high amounts of

ammoniated products.

EXPERIMENTAL PROCEDURE

The present research covers a two-year study with
hybrid corn harvested as silage during the 1967 and 1968

crop years on Michigan State University dairy farms.

Experiment I

Whole plant corn (excluding roots) of the Michigan
400 variety was harvested with a two row silage harvester.
The corn plant material. fine chopped. was transported
to the Michigan State University dairy barns in self-
unloading wagons. and weighed prior to ensiling. Two
vertical. concrete stave silos (3.66 x 6.71 and 3.01 x
12.19 m) were filled with approximately 32 and 50 tons
of the fresh material containing 39 and 35% dry matter
(D.M.). At the time of ensiling. randomized samples of
the green chopped corn were collected for subsequent

chemical analyses.

44

45

Addition of Anhydrous Ammonia
£g_§reen Chop Corn

A high-pressure tank equipped with a relief
valve. pressure gauge. and a liquid withdrawal valve.
of 200-gallon capacity was used for application of
ammonia. By setting the relief valve the ammonia was
added to the silage at a rate of 2.8 kg per metric ton
of chopped corn. A plastic line from the ammonia tank
was connected to a water hose. set to deliver at the
blower 30 kg of water per metric ton of green material.
Mixing occurred as the dissolved ammonia was blown into
the silo. The other silo (35% D.M.) was filled with
untreated material and used as control silage.

Fresh corn samples were collected from both lots
just prior to entering the blower. One sub-sample was
immediately analyzed for dry matter content. The other
was placed in a plastic bag and stored at -3°C for future

determinations.

Dairy Heifer Feeding Trial

The experimental silage was fed to dairy heifers

primarily to determine the effects of its palatability

46

on intake. but some indication of its value for growth was
also of interest. Twenty—one Holstein heifers weighing
354 to 485 kg were allotted to two uniform groups on the
basis of body weights. The heifers were individually fed
once daily. Each group was fed corn silage ad libitum as
the only forage. in order to evaluate more clearly the
effect of the nitrogenous additive on appetite. Silage
offered and weighed back was recorded for each heifer
daily. The animals were weighed at the beginning and at
the end of the 16-day feeding period for two consecutive
days. Samples of silage were taken three times a week.
on alternate days. for dry matter and nitrogen analyses.
The only supplement fed to heifers was a 50/50 mixture of
dicalcium phosphate and trace mineralized salt. which was

supplied at approximately 50 gm per heifer daily.

:Experiment II

In a second experiment. hybrid corn from the same
field was harvested and ensiled from October 2 to Oc-
tober 11. 1967. in a similar manner as described for

Experiment I. The dry matter content of the whole plant

47

corn silage ranged from 37.8 to 39.2%. .Approximately 40
metric tons of silage was treated with 0.5% urea and
ensiled in a concrete-stave. upright silo (3.01 x 12.19 m).
A second silo was filled from alternate loads. but was

not treated with urea. The ammoniated corn silage from
Experiment I was also used in the trial.

Silage treatments were as follows: A) Silo 5.
control corn silage; B) Silo 4. corn silage plus 5.0 kg
urea per metric ton; C) Silo 10. corn silage plus 2.8 kg
of ammonia per metric ton.

The relative value of ammoniated and urea-treated
silages were determined for milk production and dry matter

intake.

.Lactation Study

Thirty-five Holstein cows were allotted to five
treatments on the basis of milk production during a
3-week standardization period. in which control silage
and alfalfa hay were fed free choice. Grain was fed at
1 kg per 3 kg milk. During the experimental period which

lasted 9 weeks. control silages were fed to two of the

48

five groups. A low protein concentrate (8.4%) was offered
to one control group. while the protein content of the
grain fed to the other group was 18.6%. The cows on
control silage plus low protein grain served as negative
control for a better evaluation of the possible effects
of the added ammonia and urea. Two groups were fed urea-
treated silage. Crude protein in the concentrate offered
to one group on urea silage was 8.4%.and the other group
received a concentrate containing 12.9% crude protein.

The fifth group was fed ammoniated corn silage and the
same concentrate (12.9%.crude protein) furnished to one
of the urea-supplemented groups. All cows were fed the
various silages ad libitum once daily as the sole forage.
and concentrates were supplied twice daily at 1 kg per

3 kg milk. Daily milk weights were recorded for all cows.
A daily composite sample of milk was collected weekly

and was tested for fat content by the Babcock procedure.
Animals were weighed on two consecutive days. 7 days after
the beginning and at the end of the experimental period.
Samples of silages were taken on Mondays. Wednesdays.

and Fridays of each week and analyzed for dry matter.

Subsamples were frozen in plastic bags and saved for

49

nitrogen analyses. Samples of the different concentrates
were also collected at various times throughout the feed-

ing period for dry matter and nitrogen determinations.

Experiment III

In October. 1968. hybrid silage corn was harvested
at approximately 37. 41 and 52%.D.M. with a self-
propelled Super-D Fox Chopper. The chopped corn was
transported and ensiled as described for the first and
the second experiment. Nearly 58 tons (37%.D.M.) and 25
tons (52%.D.M.) of whole plant corn silage were treated
with urea at 0.5 and 0.75%.1evels. respectively. at the
ensiling time in a similar manner as in Experiment II.
Approximately 35 tons of fresh material (41%.D.M.) were
treated with anhydrous ammonia at the filling time by
the process already described in Experiment I. Through
2-inch holes in the silo doors. samples were removed
with an auger during the fermentation period of the 41
and 52%.D.M. silages for pH determination. All sampling
and tests for silage samples were the same as outlined

previously. The silages were evaluated in two animal

50

performance trials. consisting of a lactation and a

nitrogen balance study.

“Lactation Study

Eighteen Holstein cows were grouped into three.
comparable lots. on the basis of milk production during
a 21—day standardization period. The standardization
ration was the same as described in the previous exper-
iment. During treatments three groups of 6 cows each
received the following rations: urea-treated corn silage
(36% D.M.); urea-treated corn silage (52% D.M.); and
ammonia-treated corn silage (42%.D.M.). The length of
the feeding trial was 7 weeks following 10 days for
adjustment to rations. Cows on ammoniated silage and
35% D.M. silage treated with urea continued on treatment
until 11 weeks. The silages were fed ad libitum with a
concentrate mixture formulated to contain approximately
10%»crude protein. The grain was fed to all cows at the
same ratio (1:3) as during standardization. Changes of
the amount of grain supplied were made based on the mean

persistencies of each group. During the experimental

51

period. daily feed consumption and milk production were
recorded as in the previous experiment. Likewise. all
milk and all feed sampling procedures were similar to

those previously reported.

. Digestibility and Nitrogen
Balance Study

A digestibility and nitrogen balance trial was
conducted immediately after the 7-week feeding period
on all cows used during the lactation study.

The system employed for urine collection was
developed by Dr. Clifford Beck of the Michigan State
University Veterinary Science Faculty. It consisted of
a plastic funnel—like apparatus. surgically sutured to
the skin surrounding the vulva. Branding cement was
applied to make the device spillage-free. Urine excreted
was directed through a tube into a storage container.
Feces were collected in galvanized. stainless steel pans
set in the gutter behind the cows. This type of pan is
characterized by a high back in order to prevent possible

losses.

52

The collection period for all groups was origi-
nally designed to last 7 days. but because of a lack of
good-quality silage. cows on silo 12 (52%.D.M.) were
terminated after 5 days. The other groups continued to
7 days. Two days were allowed for adjustment to the
collection apparatus. Feed. orts. urine. and feces were
individually weighed at 24-hour internals. One percent
of the daily urine volume. five percent of the feces
weight and 20 to 100% of the orts were frozen daily.
Samples for the total period from each cow were thawed
and composited for analyses. Milk weights were recorded
for each cow and a daily composite sample was collected
for three alternate days. Milk samples were treated with
formaldehyde during the collection period. as a preserv-
ative and kept at 4°C until analysis. Fecal. urinary
and milk nitrogen were determined by the Kjeldahl method
on fresh samples. Dry matter on feces was analyzed as

previously described.

Experiment IV

Samples of untreated. urea-treated and ammon-

iated corn silages were used for this experiment. This

53

was an attempt to detect possible nitrogen losses from
samples of silage exposed to different temperatures for
varying lengths of time. Anhydrous ammonia was added
to the green-chopped corn only at the time of ensiling;
but in case of the urea-treated silage. some was treated
either at the time of ensiling or at the time of feeding.
Some control and urea silages were sampled immediately
after the removal from the silo by the silo unloader.
Samples were sealed in Plastic bags. The ammonia silage
was taken four feet below the top surface of the silage.
All samples were handled in such a way as to minimize .
nitrogen losses and air exposure. The urea-treated
silage was divided into 5 portions. One portion was
immediately analyzed for day matter and total nitrogen.
Another was exposed to the barn temperature (average 20°C)
for 10 hours. The three remaining portions were placed
in three different ovens. set at 31°. 45° and 52°C for
10 hours. Following the lO-hour period. samples were
ground and analyzed for nitrogen and dry matter.

Another untreated corn silage sample was taken
directly from the top of the silo immediately after

mechanical unloading of 420 kg of silage. Exactly 190 kg

54

of that silage were treated with 0.71% feed grade urea
(45% nitrogen) and 0.75% ammonium polyphosphate (AMP).
One sample was collected after the chemical treatment.
Two Holstein cows were offered 45.4 kg of silage.
One cow received control silage and the other was offered
urea-AMP-treated silage. Additionally. 9 kg of each
silage were not fed but were placed in two galvanized
bushel containers exposed to the barn conditions in
order to compare the effect on the silage of feeding
conditions (such as contamination by saliva. water and
dirt from the cow). The barn temperature was measured
with a thermometer placed approximately 10 cm above the
silage buckets. The "fed" and "not fed" silages were
exposed to the stated conditions for 20 hours. Sub-
samples were taken after 10 hours and at 20 hours. Barn
temperature during the period averaged 21°C. All samples
were ground and analyzed for moisture. pH and nitrogen.
The ammoniated silage was ground in a Wiley mill
using a 3/8" coarse screen. One portion of the ground
silage was analyzed as described. The remainder was
placed in the cooler at 3°C. A sub-sample of 500 gm of

the remaining silage was taken daily from the sealed

55

plastic sack and placed immediately into a hot air oven
for 10 hours. Temperatures of 35°. 52°- and 75°C were
compared for three successive days. During the drying
process the forage sample was spread in a thin layer of
approximately half inch depth in a shallow tray. After
10 hours at the different temperatures the forage was
removed from the oven. placed immediately in glass jars.

and stoppered firmly for future determinations.

CHEMICAL ANALYSIS

Dry Matter.ng. Total Kjeldahl Nitrogen.
Crude Protein Equivalent

Dry matter content of green chopped corn. corn
silage. orts. and feces were determined in duplicate by
drying in a forced-air oven at 80°C for 48 hours. Dry
matter content of the ground grain was measured by drying
in a hot-air oven at 100°C for 5 hours.

The pH was determined with a Beckman pH meter.
by placing the external glass electrode of the Beckman
into a mixture of approximately 5 gm of wet silage and
20 ml of distilled. deionized water at room temperature.

Total nitrogen was analyzed by the Kjeldahl
method in triplicate for all feed and fecal samples. but
air-dried ground grain samples were analyzed only in
duplicate. Crude protein equivalent was obtained by
multiplying the total nitrogen value of each sample by

the factor 6.25.

56

RESULTS

Chemical Composition of Silages
and Concentrates

pry Matter

The average dry matter content of silages fed
in Experiments I. II and III are presented in Table l.
Silages which received no additive fed only in trials
I and II. averaged 32.6 to 35.7%.dry matter (D.M.).
while the two silages treated with ammonia contained
35.9 and 41.9%.D.M. Urea-treated silages ranged from
35.8 to 52.4% D.M.

Differences in dry matter levels were related
to date of harvest. Harvest was intentionally delayed
in order to obtain the high dry matter levels (52%) of
a urea-treated silage in Experiment III.

Grain dry matter levels (Table 2) averaged 86.3%

with a range of 86.0 to 86.7%.

57

58

IF:

Data on pH were not analyzed statistically be-
cause of the limited number of observations. Values of
between 3.64 (for the ammoniated silage. 41%.D.M.) and
4.63 (for the urea-treated silage. 52%.D.M.) were ob-
served. Under the conditions of this study. neither urea
nor ammonia additions appeared to have a consistent ef-
fect on pH. The lack of effect due to the additives may
have been partially due to variations in dry matter.
however. urea-treated silage having the highest dry

matter level (52%) also exhibited the highest pH (4.63).

Crude Protein

All of the nitrogen additives markedly increased
the crude protein equivalent of the silages above that

of comparable controls (Table l).

 

59

 

 

 

 

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60

Urea was added to the high dry matter silage
(52%) in such amount (0.75%) as to furnish approximately
equal nitrogen on a dry basis. as the lower dry matter
silage treated with 0.5% urea. Ammonia was added to the
silages at 2.8 kg per metric ton. which was equivalent
to 0.5% urea. Silage analyses showed that ammonia
supplied approximately 31.7 and 23.0% of the total ni-
trogen of silages harvested during 1967 and 1968. re-
spectively.

In 1967-68 added ammonia accounted for 31.7 of
the total ration nitrogen fed the heifers and 20.1%
furnished to the cows in the lactation study. In Ex-
periment III the percentage of the total ration that
came from ammonia was 9.2%.

Urea nitrogen accounted for approximately 21.7
and 19.0% of the total nitrogen fed with low- and
medium-protein rations during the Experiment II. About
20.4 and 16.4% of the total ration nitrogen was supplied
by urea in thelow and high dry matter silages fed in

Experiment III.

61

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62

Other Constituents

In general. the addition of either urea or am-
monia did not alter the proximate constituents of silages
other than the crude protein content.

Table 2 shows the ingredient composition and
chemical analyses of the concentrates used throughout

the feeding trials.

Heifer Growth Trial (Experiment I)

Data from this trial are shown in Table 3. The

statistical analysis employed was the Student t-test (92).

TABLE 3.--Intake and growth of dairy heifers fed ammon-
iated corn silage

 

 

 

Treatment
Item “* ,
Control Ammonia
(0.28%)
Number 10 11
Dry matter intake (% of B.W.)a 0.94* 1.06
Average daily gain (kg) 1.06** 1.18
Feed utilization (kg D.M./kg gain) 8.51 8.46

 

aB.W. = body weight
*Significant lower (P < 0.01).
3*Nonsignificant (P'< 0.10).

63

Dry matter consumption was significantly lower (P < 0.01)
for heifers fed the control than the ammonia-treated
silage. Heifers fed the ammoniated silage also had
greater body weight gains (0.12 i 0.12 kg per day dif-
ference. P < 0.15). Feed utilization (kg D.M. per kg
gain) was not significantly different. but the treated
group had a slightly higher feed utilization than the

control.

First Lactation Study (Experiment II)

In Table 4 are presented the feed consumption
data collected from all cows during the feeding period.
Orthogonal contrast (92) was the technique used for
testing differences among treatments.

The silages were of good quality as indicated
by the silage dry matter intakes. However. intakes were
significantly depressed (P < 0.05) when the low protein
concentrate (8.4%.C.P.) was fed. The depressed consump-
tion was due to the low protein content of the rations.

rather than any silage characteristic. Total dry matter

64

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65

intakes followed a trend similar to that observed for
corn silage intakes except that the group receiving urea-
treated silage and medium-protein concentrate exhibited
highest intakes but differences were not significant
from the other two rations containing approximately
equal levels of nitrogen.

Milk yields per kg dry matter intake among all
groups were not significantly different (P < 0.05).

Production performance and body weight gain data
are presented in Table 5. Because of lower protein con-
sumption. the negative control group produced signifi-
cantly less (P < 0.05) than all other groups. except the
low-protein group fed urea-treated silage which approached
significance (P < 0.05). Average production of cows fed
urea-treated and ammonia—treated silages with the medium-
protein concentrate was about the same as those on posi-
tive control silage. Because of similar production during
standardization. persistencies followed a pattern similar
to that for milk yields.

Body weight changes were significantly lower
(P < 0.05) for the negative controls than the three groups

receiving adequate protein. Gains on urea silage and

66

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003

 

 

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67

low-protein concentrate were intermediate and not signif-

icantly different from any of the treatments.

Second Lactation Study_(Experiment III)

Corn silage and total feed intakes. expressed as
a percentage of live weight. were higher (P < 0.05) for
the cows on treatment A than the B and C (Table 6). Milk
yield per kg dry matter intake was significantly higher
(P < 0.05) for cows on B than for those on A but not sig-
nificantly different from C.

Average milk yields did not vary significantly
but persistencies were higher for groups receiving urea-
treated than ammonia-treated silages (Table 7). Differ-
ences between the lower dry matter urea-treated and the
ammonia-treated silages were significant (P < 0.05).

Milk fat production was significantly higher
(P < 0.05) for treatment A than B and C. but there was
no significant difference in milk fat percentages among
the three groups. Gains were about equal in group A and

C. but B was lower (P < 0.05) than A.

68

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69

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on

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70

Dry matter intakes for Groups A and C for the
total period of 11 weeks are given in Table 8. Silage
intake and total dry matter intake expressed as a per-
centage of bodyweight were significantly higher
(P < 0.005 and P < 0.025. respectively) for treatment A.
There was no significant difference in milk yield per kg
of dry matter intake between the groups.

TABLE 8.--Dry matter intake of cows as affected by added
ammonia or urea to corn silages (11~week

 

 

 

 

average)
Treatment
Item A C
(Urea-36% D .M.) (Ammonia-42% D .M.)
Corn silage (% of B.W.) 1.73* 1.23
Total (% of B.W.) 3.19** 2.53
Milk yield/kg D.M. 1.43 1.50

 

*Significantly higher (P < 0.005)
**Significantly higher (P < 0.025)

Milk production and persistency were significantly
higher (P < 0.05). for the cows that were fed the silage

treated with urea. Fat production and percentage of fat

71

in the milk were also higher (P < 0.01 and P < 0.10.
respectively) for group A (Table 9). Body weight changes

showed no significant differences between treatments.

Digestibility and Nitrogen
Balance Studies

Immediately after the 7-week feeding period all
the cows were used in a digestibility and nitrogen bal-
ance study. The results of this trial are given in
Tables 10. 11. and 12. All three groups were in nega-
tive nitrogen balance; group C only slightly but the
urea-fed groups to a greater extent (Table 10).

The proportion of the ingested nitrogen appearing
in the milk was 46. 45 and 39%.for the respective rations.
Nitrogen excreted in the urine made up 26. 23 and 21%
of the total nitrogen ingested. The proportion of in-
gested nitrogen excreted in the feces ranged from 40 to
48%. The analysis of variance of the percent of ration
nitrogen secreted in milk. urine and feces failed to
detect any significant differences even at the 10%

probability level among treatments.

72

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.Amo.o v as “mamas saucmosmscmsm.

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73

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mocmamn cmmouuflz

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v.HH Hm mm on OCHHS CH
m.HH mm mg 0% XHHE CH

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74

 

 

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nmfln mo mucoaoflmmmoo coflummeQII.HH mamma

75

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76

No significant difference was observed in nitrogen
balance between the three diets. Nitrogen intakes were
highest on treatment A. followed by B and then C. Mean
differences in nitrogen intake were significant (P < 0.05).

Coefficients of digestibility of dry matter. crude
protein and non-protein dry matter were similar in all
treatments (Table 11).

Cows on ration A secreted a higher percentage
(P < 0.05) of the total digested nitrogen in both milk
and urine than the other two groups (P < 0.05. Table 12).
The percentage of the digested nitrogen in milk for group
B was greater than that observed for the ammonia treat-

ment. but differences were not significant (P < 0.05).

Study on Nitrogen Losses from Corn Silages
Treated with Various NPN Sources
No consistent losses of nitrogen resulted from
the drying temperatures or methods of exposure imposed
on the urea-AMP-treated silage (0.72% urea and 0.75%.AMP).

or ammoniated silage (0.28%).

77

Concentrations of Kjeldahl total nitrogen (on a
dry matter basis). dry matter percentages and pH values
for the silages measured at varying temperatures are pre-
sented in Tables 13 and 14.

The addition of urea and AMP to the control silage
(0.71 and 0.76%. respectively) at the time of feeding in-
creased the nitrogen concentration of the silage which
did not change for 20 hours under barn conditions (either
sitting in an open bucket or in front of the cow).

Addition of urea and AMP to the control silage
at the time of feeding produced a slight rise in pH com-
pared to the control when the silage was exposed to the
barn temperature for several hours. A trend toward in-
creased pH was detected as temperatures increased from
20°C to 75°C but this was not consistent for all treat-

ments.

78

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79

TABLE l4.--Effects of time of exposure to the environ—
mental barn conditions on nitrogen content and

pH of untreated and urea-AMP-treated corn

silages

 

 

Sample designation

Time of exposure (hour)

 

 

0 10 20

Untreated silage (not fed)a

Nitrogen % (D.M.) c 1.192 1.199 1.173

Dry matter (%) 37.33 38.38 38.71

pH 3.83 3.92 3.94
Ort from untreated silage (fed)b

Nitrogen %I(D.M.) 1.192 1.260 1.229

Dry matter (%) 37.33 37.85 36.79

pH 3.83 3.85 3.83
Treated silage (not fed)

Nitrogen %I(D.M.) 2.296 2.150 2.218

Dry matter (%) 37.46 38.32 38.37

pH 3.90 3.94 3.96
Ort from treated silage (fed)

Nitrogen %I(D.M.) 2.296 2.273 2.308

Dry matter (%) 37.46 39.03 41.03

pH 3.90 3.94 4.02

 

aNot fed = exposed in a bucket in front of the cow.

bFed = silage fed to a cow.

c
D.M. = dry matter.
at the time of feeding.

Treated with 0.72% urea and 0.72%.AMP

D ISCUSS ION

Urea increased the crude protein equivalent of
silages at 36 and 52%»D.M. by 4.1 and 4.2 percentage
units on a dry matter basis. which represented 35.3 and
37.2%Iof the total nitrogen. Crude protein equivalent
of silage increases in proportion to the amount of urea
added (6. 54). However. because of the difference in
dry matter content of the urea silages (36 and 52%) fed
in the second lactation study. 7.5 Kg per metric ton of
urea were added to 52%.D.M. silage to obtain crude pro-
tein equal to that furnished by the addition of 5.0 Kg
of urea to the 36% D.M. silage.

The crude protein content of the silages treated
with 2.8 Kg of ammonia per metric ton was increased by
only 3.6 and 1.8 percentage units on a dry matter basis
for the 36 and 41%.D.M. silages. respectively. Prior to
treatment. the 36%.D.M. corn silage (harvested in 1967)
contained 1.25%.nitrogen on a dry matter basis. Nitrogen

content was increased to 1.83%.by ammonia treatment. In

80

81

the case of 42%.D.M. silage (harvested in 1968) the in-
crease was from 1.20% to 1.48% on a dry matter basis.
The magnitude of increase in nitrogen by ammoniation is
within the range of that reported by Millar (69). Ammon-
iation of several by-products (molasses. citrus pulp.
beet pulp. etc.) has been conducted by different pro-
cesses. For instance. the process of ammoniating corn
silage reported by Millar differed from the process em-
ployed in this study. Ammoniation of corn silage at
155 pounds pressure and 108°C increased the nitrogen
content 2.0 percent; however. the quality of the feed
was adversely affected (69). From the data in this work
it appears that the dry matter content of the silage has
an influence upon the amount of total nitrogen fixed from
anhydrous ammonia added through water. One improved
method for ammoniating silage has been developed at the
Midhigan State University Experiment Station (36). It
involves the use of cane or wood molasses as a carrier
for the gas.

In the growth trial. heifers made good weight
gains when fed both control and ammoniated silage. The

heifers receiving the silage with ammonia showed better

82

feed intake expressed as a percentage of liveweight

(P < 0.01). The improved performance on ammoniated
silage was due to the increased crude protein equivalent
of the silage. Many investigators: Millar (70). Knodt
§£_gl, (55. 56). Magruder gt_§l. (63). McCall and Graham
(65). Magruder and Knodt (64). and Parham gg_al. (77)
have reported satisfactory body weight gains in cattle
and sheep with ammoniated products. In the previous
trials additional sources of protein and energy were
supplied. but in this study corn silage was offered as
the sole source of protein and energy. Under this feed-
ing regime. even the heifers on the control silage gained
an average of 1.06 Kg per day which is quite satisfactory
for herd replacements averaging 424 Kg liveweight.
Schmutz (90) reported reasonable weight gains of heifers
on corn silage as the only feed. In the present study.
the good gains of heifers on the untreated corn silage
may be explained by the excellent quality of the silage
and by its relatively high crude protein level (9.3%).
Daily intake of silage on wet basis averaged 27.4 Kg
(32.6%.D.M.) and 26.2 Kg (35.9%.D.M.) for the control

and ammoniated silages. respectively. Intakes of total

83

crude protein daily were approximately 865 gm for the
control and 1063 gm for the experimental group. Both
groups were fed more than the total protein allowance of
the National Research Council (74). The ammoniated
silage was found to be very palatable. In this study
ammonia contributed approximately 31.7% of the total ra-
tion nitrogen consumed. The higher crude protein content
of the ammoniated silage was probably the reason for the
increase in feed intake.

The heifer experiment was of a very short length
of time; therefore. any considerations of practical ap-
plication should be taken with caution.- Undoubtedly an
experiment of longer duration would be necessary to more
properly evaluate the ammoniated silage for heifer growth.

Corn silage and concentrate mixtures were the only
nutrients fed to cows during the lactation studies. In
the first trial. the animals fed low-protein concentrate
(8.4%) with control silage or with urea-treated silage
(0.5%) exhibited lower silage dry matter intakes than
treatments of higher protein content. The highest intake
of silage was noted for the positive control group. fol-

lowed by urea-treated and ammonia-treated silages fed

84

with medium-protein concentrate (12.9%); however. these
differences were not significant. It is interesting to
note that the highest total dry matter intake was ob-
served for cows on urea-treatment. followed by ammonia-
fed group and the positive control group. Silage treated
with 0.5%Iurea when fed with a medium-protein concentrate.
the animals consumed more than those on the same silage
fed with a low level of protein concentrate. The most
dramatic evidence of effect of total nitrogen intake on
feed consumption was shown by the very low intakes of

the negative control cows. An improvement in dry matter
intake by addition of urea to corn silage was also re-
ported by Huber g£_§l. (46). This response appears to

be due primarily to an improvement in the protein status
of the cows through increased nitrogen intake.

No significant treatment differences were ob-
served in efficiency of production per Kg of dry matter
intake. Treatment differences in milk production. per-
sistencies and body weight gains can be partially ex-
plained by the low nutrient intakes by the low-protein
groups. Both additives had a small depressing effect

on the percentage of milk fat. Low milk fat percentage

85

has also been reported by Holter gt_§l. (40) in cows on
concentrates containing various levels of urea; however.
the authors suggested that the low milk fat content was
due to the low dry matter content of the corn silage.

In the second lactation trial. one reason for
the poor production performance of cows on the higher
dry matter silages treated with urea or ammonia was again
related to the low intakes. The ammoniated silage con-
tained only 9.3%.crude protein. The ammonia—nitrogen
fixation was presumably limited by the high dry matter
content of the silage which resulted in lower added ni-
trogen per unit of dry matter. Moreover. to fully chal-
lenge the NPN sources added to silage. a low—protein
concentrate was fed (10%IC.P.). Poor response by cows
to urea-treated corn silage of high dry matter content
was previously reported by Huber gt_gl. (46). Another
possible reason for the lower production when either NPN
source was added to the higher dry matter silages was
an inferior quality of the silages, this was particularly
true for the 52%.D.M. treated silage which exhibited

visible spoilage.

86

As already reported. 0.75% urea was added to the
high dry matter silage to supply approximately the same
amount of nitrogen (on a dry basis) as 0.5% urea added
to silage with 36%.D.M. material. In the case of the
ammonia-treated silage. the nitrogen added per unit of
dry matter was only 88%.that of the urea-treated silage
and that retained was much lower. probably because of
the higher dry matter content of the crop. Corn plant
material with about the same percent dry matter as the
above-mentioned ammoniated silage was treated with 0.55%
ammonia (equivalent to 1.0% urea). Nitrogen levels in
the resulting silage were only slightly higher than those
of silage treated with 0.28%Iammonia. This observation
supports the claim that dry matter content of the chopped
corn has a marked effect on the uptake of the anhydrous
ammonia by the silage. As reported by Millar (69) the
nitrogen fixation can be easily increased by adding
larger amounts of ammonia to a moist product. However.
for a very high level of ammonia fixation increased
temperature and pressure must be applied.

On the basis of these data one might hypothesize

that urea-treated or ammonia-treated corn silages

87

harvested at high dry matter content are not adequately
consumed by lactating cows for high level production.
All the reasons for this poor response by the animals

to the NPN treated silage with high dry matter content
still need clarification. However. poor intake has been
shown as a major problem.

In the digestion study. no significant differences
were noted in the apparent digestibilities of dry matter.
crude protein or non-protein dry matter among treatments.
Apparent digestion of crude protein in this trial was
comparable to that reported by other investigators (44).
when urea comprised 0.6% of the silage; but higher than
when 0.85% urea silage was fed. Digestibilities in the
present study were lower than those reported by Huber
et a1. (45) when corn silage rations were fed with con-
centrates containing varying levels of urea. The'low
dry matter digestibilities (DMD) may have been due to
two factors: low protein rations and dry matter content
of silage. There is a general trend toward lower DMD
with higher dry matter silages; but there is also a
trend toward lower DMDs in rations which are deficient

in protein (47).

88

It is possible that not only the low protein
intake but also an inferior quality of the silage in
Experiment III contributed to lower milk production.
Nitrogen intake by cows on low dry matter silage was
higher (P < 0.05) than the two remaining groups. 0f
the ingested nitrogen. the percentages recovered in
either milk. urine or feces were not significantly
different among rations (Table 10). It is interesting
to compare the amounts of crude protein fed with the
minimum requirement established by the NRC feeding
standard (74). According to NRC all groups were se-
verely underfed with respect to crude protein. One
might suggest that the feeding of rations inadequate
in protein was the major factor for the poor production
performance. namely by the cows on ammoniated silage.
The addition of nitrogen as urea or ammonia to these
low protein rations should have improved digestibility
of the dry matter. Several researchers have shown in—
creases in dry matter digestibility of low nitrogen ra-
tions after the addition of urea (13. 15. 47. 58).

All three groups were in negative nitrogen bal-

ance. The highest loss of metabolic nitrogen was

89

observed in cows on 36%.D.M. silage treated with urea.
The low nitrogen intake is a possible explanation for

the negative balances; however. the highest percentage

of dietary nitrogen secreted in milk and urine (result-
ing in the largest negative balance) was exhibited by

the group producing the most milk which actually consumed
more nitrogen than the other groups (B and C). Expressed
as a percentage of the ingested nitrogen. urinary nitrogen
losses were 26. 23 and 21%. for rations A. B and C. re-
spectively. These percentages are lower than those re-
ported by Huber gt_gl. (45) and Holter §£_gl. (40).
Balance results showed that the group A secreted 140% of
its digested nitrogen as milk and urine. while groups B
and C averaged 113 and 106%u Huber and Thomas (47) have
recently reported that as high as 142% of the digested
nitrogen was recovered in the milk and urine from cows

on control silage fed 8.4%.crude protein concentrate.

Some attention was directed to possible non-
protein nitrogen losses during the handling of the silage.
As previously reported. corn silage treated with urea
and AMP (7.2 Kg and 7.5 Kg per metric ton) at the ensiling

time. when placed under various temperatures (ranging

90

from 20°C to 75°C. Table 13). did not undergo any signif-
icant decrease in nitrogen. neither did exposure of corn
silage treated with urea and AMP at barn temperature
affect the nitrogen content of the silage (Table 14).
Small and inconsistent differences noted among treatments
regarding nitrogen levels might be due to: 1) lack of
complete uniformity in the different portions of silage
subjected to the various temperatures or method of ex-
posure. and 2) the techniques for determining nitrogen
losses were not sufficiently precise to differentiate
among very small changes that might have occurred. In,
other words. the results are within the limits of ex-
perimental error. A trend toward increased pH due to
barn exposure and higher temperatures was noted in most
of the treatments. but this was not consistent. The rise
in pH with increasing temperature or length of exposure
time may be explained by the loss of volatile organic

acids.

SUMMARY AND CONCLUSIONS

Holstein heifers and lactating cows were used to
compare the nutritive value of ammoniated corn silage to
silage treated with urea.

The dry matter content in the silage appears to
be more responsible for changes in pH than the addition
of urea or ammonia at the levels used in this study.

The highest pH measured (4.63) was in high dry matter
silage (52%) to which 7.5 Kg of urea were added per
metric ton.

The crude protein equivalent of the urea-treated
silages at 36 and 52%.D.M. increased by 4.1 and 4.2 per-
centage units on a dry matter basis. Silages treated
with anhydrous ammonia (0.28%) increased in crude protein
equivalent by 3.6 and 1.8 percentage units on a dry matter
basis at 36 and 41%.D.M,. respectively. In contrast to
conclusions by Millar (69). it appears that the dry
matter content of the silage has a marked influence on
the amount of nitrogen fixed by application of ammonia

in the aqueous form.

91

92

The process for ammoniating corn silage employed
in the present study has been recently improved through
using molasses as a carrier.

In the heifer trial. intakes and gains of the
ammoniated—silage group were better than the control
group. probably because of the increased nitrogen con—
tent.

In the first lactation study. total dry matter
and silage dry matter intakes. milk yields. persistencies
and body weight gains of cows on the negative control
ration were significantly lower (P < 0.05) than the
groups on normal protein diets. The group on urea
silage plus low-protein concentrate was lower (P < 0.05)
in silage dry matter intake than the positive control.
and lower in total dry matter intake than the group on
urea-silage fed with a medium protein grain. On the
basis of these data it was concluded that dry matter in-
takes were significantly improved either by a higher
level of protein in the concentrate or by addition of
urea or ammonia to the silage. The poorer performance

of the low protein rations was partially due to reduced

93

nutrient intake. The ammoniated silage was as palatable
as the control or urea-treated silages.

In the second lactation trial. fixation of an-
hydrous ammonia (with water as a carrier) was decreased
by the high dry matter content of the silage. Lower
intakes and milk yields resulted from feeding NPN-treated
silages (either urea or ammonia) which were higher than
40% in dry matter. The decreased nitrogen fixation by
the ammoniated silage resulting in a ration of lower
protein content (than groups receiving urea-treated
silages) may have been partially responsible for the
poor performance of this group. Based on these findings.
one may conclude that urea— or ammonia-treated silage
containing a high level of dry matter is not sufficiently
consumed by lactating cows to maintain high milk yields.
However. data are not sufficient to explain the reason
for the poor intakes by cows fed urea or ammonia silages
of high dry matter content.

Dry matter digestibilities among treatments were
somewhat lower than those reported in some previous
studies (45. 47). Additions of ammoniated products to

rations have adversely affected the digestibility of

94

many components in the ration (96); but when this occurred.
ammoniation was under conditions of high temperature and
pressure.

NPN-treated silages were subjected to various
temperatures but no consistent losses of nitrogen were
noted. On the basis of this trial it appears that un-
treated or treated silages can be exposed to the barn
atmosphere for a prolonged time without loss of nitrogen.

Based on the findings in this study. it is con-

cluded that:

1) On an equal-nitrogen basis anhydrous ammonia
added to corn silage is used for milk production
and heifer growth as effectively as urea. but it
must be added to silage of less than 40% dry

matter for optimum results.

2) When either urea or ammonia is added to silage
which is in excess of 40%.D.M.. poor performance

results.

3) Loss of nitrogen from ammonia-treated or urea—

treated silages under barn conditions. before

95

the cow. or due to heating up to 75°C are insig-

nificant.

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