Group Title: Animal Science mimeograph series - Florida Agricultural Experiment Station ; AN 64-12
Title: Comparison of a self-fed concentrate and a supplemented forage diet for developing beef bulls
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 Material Information
Title: Comparison of a self-fed concentrate and a supplemented forage diet for developing beef bulls
Series Title: Animal Science mimeograph series
Physical Description: 21 p. : ; 28 cm.
Language: English
Creator: Hentges, J. F ( James Franklin ), 1925-
Capote, Fausto A., 1938-
Neal, F. C
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1964
Subject: Bulls -- Feeding and feeds -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (p. 19-21).
Statement of Responsibility: J.F.Hentges, Jr., F.A. Capote and F.C. Neal.
General Note: Caption title.
General Note: "July, 1964."
Funding: Department of Animal Science mimeograph series ;
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Bibliographic ID: UF00072938
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 77275540

Full Text

/An.c. g-/

Animal Science 7 Florida Agricultural
Mimeograph Series AN 6 2 C Experiment Station
M a i 3 Gainesville, Florida
July, 1964


J. F. Hentges, Jr., F. A. Capote and F. C. Neal

Although the effects of undernutrition on the potential reproductive
capacity of beef bulls has been the subject of several research publi-
cations which were recently reviewed by Meacham et al. (1962), virtually
no research has been conducted on the effects of fattening (overnutrition)
on semen characteristics, libido and mating behavior of beef bulls.

Since 1960, the fattening of young beef bulls in performance tests
has become routine in registered cattle herds and bull test centers.
In these tests, weight gains are recorded from weaning or shortly there-
after to about 13 to 15 months of age. Bull performance testing, as
currently practiced, is highly recommended by cattle geneticists who
have learned that the ability of beef cattle to gain weight is an
inherited characteristic.

To illustrate the lack of knowledge regarding precise feeding
methods for bull performance tests, it should be pointed out that:
I. Bull performance tests were started to detect bulls which gained
weight faster than other bulls under identical test and pre-test con-
ditions. To get a true comparison of gainability, all bulls must
enter a test with the same chances to gain. This almost restricts
performance testing to "within herd" tests on bulls which were raised
together, weaned at the same time and fed similarly. 2. Cattle breeding
specialists have always discouraged the comparison of results (average
daily gain on test and/or lifetime average daily gain) among .different
bull performance tests on different ranches or in different bull test
centers. The obvious reason for such action was that feeding and manage-
ment practices, especially the pre-test handling of bulls, is sure to
be different. 3. The original proponents of bull performance testing
did not specify a high-concentrate feeding program designed to obtain
maximum weight gain but specified only that all bulls should be provided
free access to the same feed.

The recent trend toward the use of high-concentrate diets in bull
performance tests to get maximum gains is not based on research findings;

/ Dept. of Animal Science, Florida Agricultural Experiment Station,
Gainesville, Florida.


rather, the high cost of such feeding programs plus field reports
showing the desirability of testing breeding cattle on roughage diets
should discourage this practice. Koger and Knox (1951) stated that
"growth of beef cattle prior to feeding age was positively correlated
with gain in the feedlot"; "that when environment is constant for
different animals, there is a positive relationship between gains made
at different periods (ages)"; that "from a practical viewpoint, adapt-
ability to range conditions, as measured by growth, showed a positive
correlation with feedlot gain". Their research would indicate that
the feeding of roughage diets in performance tests would effectively
select bulls with the ability to gain fastest on either high-roughage
or high-concentrate diets. Warwick et al. (1964) in a study of twin
beef bulls fed on high and low concentrate rations stated "the results
suggest that the safe procedure would be to select beef breeding stbck
under an environment similar to that in which their descendants will
be produced commercially". In the Southeastern Gulf Coast states, most
beef calves are raised to weaning on pasture and are grown to maturity
on pasture or high roughage diets. Less than half of the offspring in
commercial herds will be fattened for slaughter on high concentrate
diets. This situation plus the cost of imported concentrate feed
virtually dictates that performance testing of beef bulls be done on
high roughage diets. If it is desired to measure inherited ability to
fatten quickly on high-concentrate diets, a companion test with half-
brother steers grown on a high-roughage diet but finished on a high-
concentrate diet would be preferred. Because.a record of a bulls average
daily weight gain is of less value than his gain of edible lean, fat,
and bone which can be determined only by carcass testing, several beef
cattle breed associations sponsor carcass tests as additional means of
identifying superior herd sires.

The objective of the experiment reported herein was to measure the
comparative effects of feeding a high-concentrate and a high-roughage
diet on the feedlot performance and potential reproductive potency of
beef bulls during a performance test and the subsequent months prior
to their sale as commercial bulls at 22 to 25 months of age.

Experimental Procedure

The experimental animals were fall weaned Angus, Hereford and
Brahman bulls which averaged 570 Ib. in weight and 325 days in age at
the beginning of the experiment on November 19, 1962. They were assigned
to two feed treatment groups according to breed, age and weight.
Group I was fed forage ad libitum while Group II was fed concentrate
ad libitum.

The experiment was divided into two phases with each phase charac-
terized by a change in composition of the diet offered to the forage
fed bulls. Phase I was a 196-day performance test which ended on June
3, 1963, ,In this phase, one group of 14 bulls were hand fed 7 lb. of a


concentrate mixture per head once a day plus all of the corn silage
that they would voluntarily consume. A similar group of 14 bulls were
offered the same concentrate mixture ad libitum from a self-feeder.
Table I shows the proximate composition of the diets during Phases I
and II. Each group was kept in a fertilized grass pasture which pro-
vided 0.5 acres of grazing per head.

Phase 2 was a 140-day extension of the same treatments with 20
of the same bulls. In Phase II, the forage was changed from corn
silage to fertilized grass pasture and the amount of concentrates offered
to the group fed forage ad libitum was increased from 7 to 8 Ib. per
head. The bulls fed concentrates ad libitum were given free access to
the same concentrate feed mixture from a self-feeder. The bulls offered
forage ad libitum were provided with 1.0 acre of Coastal Bermudagrass
pasture per head while the bulls fed the concentrate ad libitum were
provided with 0.5 acres per head.

Shade, well water and a mineral mixture was available in each pas-

Liveweights were recorded every 28 days.

Semen was collected by electroejaculation with a Nicholson all-
transistor ejaculator. The procedure involved insertion of a 2 1/2
inch probe into the rectum, massage of the testicles, electrical stim-
ulation rhythmically with voltage being increased stepwise until ejac-
ulation was complete. The semen was collected in a glass tube. If
visual observation of the sample revealed pus cells, low concentration
of sperm cells or contamination, a second ejaculate was obtained.
Cupps et al. (1957) compared ejaculation with the artificial vagina
and electrical stimulation methods and concluded that the electro-
ejaculator resulted in greater volume, lower concentration and no
differences in morphologically normal live or actively progressive
sperm. Hulet t al. (1964) Dn a comparison of ejaculation methods with
rams concluded that "natural ejaculates are preferable to electro-
ejaculates for predicting fertility", "electroejaculation should be
limited to use as a supplement or alternate to natural ejaculation when
the natural ejaculate is either impossible or impractical to obtain".

Semen was collected and evaluated on the I, 28, 112 and 196 day of
Phase I and on the 28 and 56 day of Phase II. The semen criteria studied
were sperm vigor, concentration and percentage of live and abnormal
cells. Semen vigor was scored numerically as follows:

1. Very good.
2. Good.
3. Fair.
4. Poor
5. None


Ingredient Pounds, air-dry

Corn meal, yellow 54.0
Citrus meal, dried 15.8
Soybean oil meal, e0% 3.5
Cottonseed meal, 41% 3.5
Urea, 262/. 1.0
Molasses, cene, standard 5.0
Alfalfa meal, dehydrated, 17, 5 0
Mineral and vitamin mixture 2.0
Corn cobs, coarsely ground 10.0
Aurofac 10 0.0375
Defluorinated phosphate 0.2

TOTAL 100.0

a Crude protein content averaged 13.3%

b Mineral mix contained 18.9% calcium, 5.5% phosphorus, 30% sodium chloride, 1.4% iron,
0.108% copper, 0.01/ cobalt, 0.48% manganese and 0.01% iodine. Vitamin mix contained
10,000 U.S.P. units of Vitamin 02 per lb. and was adjusted to provide an average intake
of 20,000 I.U. vitamin A per day.

Concentration of sperm cells in semen samples was scored numerically
as follows:

1. Very concentrated
2. Concentrated
3. Milky but dilute
4. Watery

The number of sperm cells per cubic millimeter was estimated from
the sperm concentration upon immediate microscopic examination of the
semen sample. Semen motility, vigor, percent of live and abnormal
cells were evaluated and recorded immediately after collection. A
live-dead stain was used to estimate the percentage of live sperm cells.

During Phase I, adhesion scores were recorded to indicate the amount
of connective tissue joining the raphe of the penis to the raphe of
the sheath at the tip of the penis in the region of the "galea glandis".
These adhesions are frequently termed "penis-sheath epithelial fusion".
The following system was used to score the extent of adhesion:

1. None
2. 15% adherence
3. 30% adherence
4. 45% adherence
5. 60% adherence
6. Penis not extended

During Phase II, the experimental animals were checked for grazing
and non-grazing activity to indicate the relative amount of each kind
of exercise taken by each group. They were checked for activity at
15-minute intervals during the daylight hours on three consecutive
days: September 4, 5 and 6, 1963. Records of temperature and relative
humidity were recorded for correlation with the activity data.

Libido and mating behavior were evaluated twice during Phase II,
in the summer on August 23 and in the fall on October 23. This was
done by exposing each bull individually to an estrogenized heifer which
was in simulated standing heat (estrus) and secured in a breeding chute.
The heifers were estrogenized by an intravenous injection of 4 ml. of
diethylstilbestrol. This was administered on the day prior to the
mating behavior test. Each bull was allowed a maximum of 10 minutes
with the heifer. Records were kept on the degree of interest displayed
by the bull, the number of mounts made, the time interval to first
mount and the number of matings completed. Records of temperature and
relative humidity were correlated with mating behavior. The following
system was used to score libido and mating behavior:


I. No interest.
2. Smelled, extended penis.
3. Mounted without an erection
4. Mounted but did not mate in 5 attempts or 10 minutes.
5. Mounted and mated on 2nd to 5th attempts.
6. Mounted and mated on first attempt.

Results and Discussion

Feed Intake. During Phase I, the average daily feed intake per
bull by the group fed concentrates ad libitum was 15.3 Ib. of the
concentrate mixture. The bulls offered corn silage ad libitum consumed
22.8 lb. corn silage plus 7 lb. of the concentrate mixture. Although
the average daily gains were smaller during Phase II, bulls in the
concentrate and forage fed groups consumed an average of 22.8 and 8.0
Ib. respectively of the concentrate mixture per head per day.

Weight Gains. The initial and final average weights were 590
and 1,230 lb. in the group fed forage ad libitum and 550 and 1,305
lb. in the group fed concentrate ad libitum. Higher gains were recorded
during Phase I than during Phase II.

As illustrated in Table 2, bulls fed concentrates ad libitum had
very high average daily gains of 2.48 and 1.95 Ib. during Phase I and
Phase II, respectively. The bulls receiving forage ad libitum made
lower but very satisfactory average daily gains of 2.05 and 1.46 lb.
for Phase I and Phase II, respectively.

Statistical analyses of weight gain data on all bulls revealed a
significant (P <.01) difference between phases and a dietary treatment
effect (P <.01) in Phase II.

Feed Cost for Each Method of Feeding. Table 3 shows a comparison
of the total feed ccsts per group of bulls during the two phases of
the experiment. The difference in feed cost per bull between the two
groups was $35.80 and $60.77 more for the group fed concentrates ad
libitum during Phase I and Phase II, respectively. The difference in
cost per bull per day between lots during Phase II was 0.26 dollars
higher than for Phase I, due to the larger daily consumption of
ccncentrates- by-the concentrate-fed bulls during Phase II.

Adhesions. Watson et al. (1956) and Wiggins et al. (1953) have
reported that penis-sheath separation was closely related to body
weight in sheep but that age also had a direct effect. Baker and
Vandemark (1952) observed that during the period from first sexual
interest to first ejaculation, the penis grew and developed rapidly,
the glans penis was freed from the prepuce and it underwent changes in


Forage Concentrate
ad libitum ad libitum

Av. initial weight, Ib. 590 550

Trial length, days

Phase I 196 196
Phase II 140 140

Av. daily gain, Ib.

Phase I 2.05 2.48
Phase II 1.46 1.95

Av. final weight, lb. 1230 1305


Phase I P Ihase L
Forage Concentrate Forage Concentrate
ad libitum ad libitim ad libitum ad libitum

Concentrate costs, dollars

Total cost 654.30 1,424.97 380.12 1,087.32
Cost/head/phase 46.70 101.78 38.01 108.73
Cost/head/day .24 .52 .27 .78

Silage costs, dollars

Total cost 269.49 -- 77.92 ---
Cost/head/phase 19.25 --- 7.79 ---
Cost/head/day .10 --- .06 -

Pasture costs, dollars

Total costs 69.62 69.62 42.84 21.42
Cost/head/phase 4.97 4.97 4.28 2.14

Total cost 993.41 1,494.59 530.88 1,108.74
Total cost/head 70.96 106.76 50.10 110.87
Difference in cost per bull 35.80 60.77

- 9-

shape and size. In the latter part of this period, protrusion of the
penis from the prepuce became possible. According to Ashdown (1960)
when the bull calf is 3 to 5 months old, spermatogenesis begins in the
testes, gross separation between penis and sheath commences, and the
penis appears to elongate relative to the ventral abdominal wall. Later,
at an age of approximately II months, mature sperm appear in the ejac-
ulate and the penis becomes completely separated from its sheath.

Table 4 shows that at the beginning of this experiment and on the
28th day of Phase I, the percentage of penis-sheath epithelial fusion
was approximately 50 in both groups. The penis of each bull was pro-
trusible but complete separation had not been achieved. A considerable
decrease in percentage of adherence was observed when the bulls in both
groups reached approximately 800 Ib. At this stage, separation of the
free end (collum glandis) reached the base of the sheath on the ventral
surface of the penis. As previously observed by Ashdown (1960) the
diverticulum of the sheath overlaying the dorsum of the penis was in
all animals the last part to become free. The average weights of the
bulls at the completetion of this stage was about 800 lb. These weights
are higher than the following reported by Ashdown (1960): 450 Ib. for
Jersey bulls and 525 Ib. for Galloway x Ayrshire bulls. Of related
interest is a report by Carroll et al. (1964) that the percentage of
persistent penile frenuli was highest in the Angus breed and that this
characteristic was not always detected by the electroejaculator method
of semen collection.

Semen Characteristics

Data on semen characteristics are shown in Table 4 for Phase I
and in Table 5 for Phase II.

Volume. Extensive study by Vandemark (1956) has shown that average
semen volume in young dairy bulls ranges from 2.3 up to 5.0 ml. per
ejaculate during the first two post-puberal years. Flipse et al. (1953),
compared the effects of feeding four different levels of energy intake
(70, 100, 115 and 130 percent of the recommended T. D. N. intake) to
17 to 22-month-old dairy bulls and observed the following narrow range
of average semen volumes: 3.6 and 3.7 ml. per ejaculate for the low
and high concentrate intakes, respectively. Olson et al. (1953) in
a similar study, reported average semen volumes of 2.7 and 3.0 ml. per
ejaculate for a low (70 percent TON) and high (130 percent TON) level
of energy intake, respectively.

The volume of semen produced by the two groups in the present
experiment was varied, ranging from 3.0 to 8.6 ml. per ejaculate. This
variation was noted among bulls within both groups and among different
collections. There was significantly more (P<.Ol) semen collected


19 Nov. 1962 17 Dec. 1962 II Mar. 1963 3 June 1963

Criteria Forage Concen- Forage Concen- Forage Concen- Forage Concen-
ad trate ad trate ad trate ad trate
lib. ad lib. lib. ad lib. lib. ad lib. lib. ad lib.

Average age (days) 321 329 349 356 433 440 517 524
Average body weight (Ib.) 590 550 628 611 798 808 998 1043
Days on experiment --- 28 28 112 112 196 196
Vigor score 3.7 3.4 2.6 2.4 2.5 2.2 3.0 2.4
Sperm motility (%) 34.6 29.3 30.0 44.3 50.0 61.4 51.4 57.1
Concentration score 3.0 3.3 3.5 3.1 3.0 2.5 2.6 2.7
Sperm count/mm3 (x 106) 307.7 239.3 225.0 300.0 317.9 353.6 375.0 367.9
Abnormal cells (0) 47.7 42.1 24.6 28.9 30.7 23.8 28.5 27.1
Live cells (%) 43.9 40.0 58.6 54.3 59.3 58.6 53.2 72.9
Adhesion score 4.4 4.9 4.1 4.3 2.1 1.6 1.2 1.1
Volume (ml) 6.5 7.6 8.'6 6.7 8.0 6.9 5.7 3.3


3 June, 1963 26 August, 1963 21 October, 1963

Criteria Forage Concentrate Forage Concentrate Forage Concentrate
ad libitum ad libitum ad tibitum ad libitum ad libitum ad libitum

Average age (days) 517 524 603 612 662 670
Average body weight (lb.) 998 1043 1125 1143 1230 1305
Days on experiment (196) (196) (280) (280) (336) (336)
Vigor score 3.0 2.4 2.0 2.3 1.9 1.9
Sperm motility (5) 31.4 57.1 53.0 60.0 70.0 66.0
Concentration score 2.6 2.7 2.5 2.3 1.9 2.4
Sperm count/mm3 (x 106) 375.0 367.9 410.0 455.0 595.0 445.0
Abnormal cells (%) 28.5 27.1 30.0 30.0 30.5 36.0
Live cells (%) 53.2 72.9 63.5 65.0 65.0 58.0
Adhesion score 1.2 1.1 -- --
Volume (ml) 5.7 3.3 3.4 5.0 5.1 3.0

- 12 -

from both groups in Phase I, the average semen volumes being 7.2 and
6.1 ml. per ejaculate for forage and concentrate-fed bulls respectively.
In Phase II, average semen volumes were 4.7 and 3.8 ml. per ejaculate
in the respective dietary groups. The variation was due to a change
from a whole collection technique during Phase I to collection of par-
tial ejaculates during Phase II; thus, providing a more concentrated
semen sample.

No statistically significant+ differences in semen volume were
found between treatments during Phase I or Phase II. Generally, the
quantity of semen produced by both groups during Phase II fell within
the range of values previously mentioned. These results are in agree-
ment with those reported by Flipse et al. (1952), who found no signif-
icant differences in volume of semen produced by bulls fed all-roughage
and all-concentrate rations.

Vigor, motility and sperm concentration. The feeding of concen-
trates ad libitum resulted in a higher motility of sperm and greater
sperm concentration throughout Phase I and during part of Phase II.
Average vigor scores at the beginning and end of Phase I were 3.7 and
3.0 respectively for the forage-fed group and 3.4 and 2.4 respectively
for the concentrate-fed group. Motility scores recorded for the group
fed concentrates during Phase I were consistently higher than values
obtained for .the forage-fed group. Average sperm concentration scores
and estimated average number of sperm cells produced by bulls receiving
concentrates ad libitum were also higher throughout Phase I and during
part of Phase II. These findings are partly in accordance with results
published by Musgrave (1951), who reported increased spermatogenesis,
attainment of puberty at an earlier age and higher oemen quality in
bulls fed 140 percent as compared to 100 percent of Tneir recommended
T. D. N. requirement (Morrison, 1956). Dunn (1952) has confirmed
Musgrave's (1951) findings. In the present experiment, the quantity
of feed offered to the experimental animals was higher than in previous
experiments and the study was continued longer after puberty. The
feeding of concentrates ad libitum resulted in higher but statistically
insignificant semen quality during Phase I. At the end of Phase II
the results had reversed with the best quality sperm being obtained
from bulls that received forage ad libitum. Bratton et al. (1961) ..
reported highest semen quality in dairy bull calves raised on a high
level of feed intake from II to 23 months of age. At 24 months of age,
bulls on a medium level of feed intake produced the highest semen
quality and this prevailed until the end of the study.

Henderson et al. (1960) and Quicke et al. (1950) showed that
moderate amounts of grass silage may be fed without impairing fertility
of bulls. Flipse etal. (1952) studied the effects of feeding large
amounts of grass silage versus large amounts of concentrates to dairy
bulls and reported no statistically significant differences in semen

- 13 -

quality between the two groups. The findings in this experiment are
in agreement since no significant differences were found in any of the
criteria used to evaluate semen quality from bulls fed concentrates ad
libitum versus forage ad libitum.

Live and Abnormal Cells. The percentage of live cells at the
beginning and end of Phase I were 43.9 and 53.2 respectively in the
group fed forage and 40.0 and 72.9 respectively in the concentrate-fed
group. Percent of live cells was higher for bulls fed concentrate ad
libitum during part of Phase II. At the last semen evaluation, when
the animals were approximately 22 months old, the percentage of live
cells was 65.0 and 58.0 for forage and concentrate-fed bulls respectively.
Similar values were reported by Flipse et al. (1952, 1961) for 20-month-
old dairy bulls. Hafez (1962) reported the percentage of normal sperm
to be 60 to 80 percent for males with high fertility.

Deviations from the normal morphology of the sperm cell have been
regarded as abnormalities (Salisbury and Vandemark, 1961). When the
number of such abnormalities reaches 50 percent of the total number of
sperm cells in the ejaculate, the male is of impaired fertility and,
as a rule, is sterile (Nalbandov, 1958). Bichan et al. (1961) reported
that 50 percent of the sperm were dead in the first ejaculate obtained
from beef calves.

In this study percentages of abnormal cells recorded at first
semen collection were 47.7 and 42.1 in the forage and concentrate-fed
groups respectively. These high values were probably due to faulty
technique since a lower incidence of abnormal cells was observed at
subsequent semen collections.

Table 6 summarizes the incidence and type of abnormalities found
in seven samples. The incidence of pus cells was highest in bulls fed
concentrates ad libitum. It is interesting to compare these data with
those reported by Carroll et al. (1963). They summarized breeding
soundness data from examinations of 10,940 bulls. Inflammation of
the seminal vesicles was observed in 338 of 7,350 bulls. This con-
dition was most common in young beef bulls confined together and fed
a gain-producing ration. Their criteria for seminal vesiculitis
were enlarged glands, pain on palpation and pus in the semen. The lat-
ter condition is described in detail by Ball et al. (1964), who related
the riding activity of bulls to the incidenceof pus cells. In our data
a higher incidence of pus cells were observed in the less active
concentrate-fed bulls.

A probable explanation for the high incidence of spheroids in semen
of both groups during Phase I was the physiological immaturity of these
bulls. No explanation is evident for the higher incidence of abnor-
malities such as proximal protoplasmic droplets and coiled tails in


Forage Concentrate Forage Concentrate
Abnormalities ad libitum ad libitum ad libitum ad libitum

Proximal protoplasmic
droplets 2 7 I I
Coiled tails 2 10 I 4
Pus cells I 5 0 3
Spheroids 5 7 I I
Head abnormalities 0 0 I 2

Distal protoplasmic
droplets 3 0 1 0
Loose heads I 0 2 0
Debris in semen 2 4 0 2
Bent tails 0 I 0 0
Accessory fluid 2 0 2 0
Short tails I 0 0 0

- 15 -

semen from the concentrate-fed bulls during Phase I. The incidence of
these abnormalities decreased considerably during Phase II.

Libido Evaluation and Matina Behavior. Libido (sex drive) is the
potential intensity of sexual behavior, measured in the male as relative
values based on the frequency and spacing of mounts, intramissions and
successful copulations (Hafez, 1962).

When libido was evaluated on August 23, 1963, the time interval
to first mount and time interval to first mating were 0.35 and 0.91
minutes respectively for the forage-fed group and 3.3 and 4.0 minutes
respectively for the group fed concentrates. The average libido score
was 5.2 for the bulls fed forage and 4.1 for the concentrate-fed bulls.
See Table 7. The libido scores indicate that 100 percent (ten bulls)
in the group fed forage accomplished mating compared to only 10 percent
(one out of ten bulls), in the group fed concentrates.

The average temperature and relative humidity recorded during
the first libido evaluation was 87.70F. and 59.7 percent respectively
and 68.70F. and 80 percent respectively during the second evaluation.

At the time libido was first evaluated, the prevailing high tem-
perature possibly had an inhibitory effect on the sexual drive, being
more noticeable in the group fed concentrates. At the second evaluation
of libido in cooler weather,criteria such as interval to first mount
and interval to first mating were improved in both groups.

In general, the lack of libido displayed by bulls in the group fed
concentrates seemed to be associated with their physical condition.
The excessive fatness of these bulls possibly had an inhibitory effect
on their sexual drive, becoming more apparent during high environmental

Activity. Observations on grazing and non-grazing exercise revealed
differences in activity between the groups. The percentages of time
spent grazing was 25.4 and 12.0 for forage and concentrate-fed groups
respectively. See Table 8. The percentages of time recorded as non-
grazing activity were 12.9 and 5.5 percent for the forage and concentrate-
fed groups respectively. Statistical analyses showed significant (P <.05)
and highly significant (P<.01) differences between groups of bulls for
non-grazing and grazing activity, respectively. Another criterion that
confirmed the lack of activity in the concentrate-fed group was the num-
ber of animals that required foot trimming. Only three feet had to be
trimmed in the group fed forage while 28 required trimming in the concen-
trate-fed group.


Criteria and Periods
Treatment Groups I 2

Interval to first mount, min.
Forage ad libitum 1.3 .21
Concentrate ad libitum 3.3 .74

Total number.of mounts
, Forage ad libitum 1.8 1.7
Concentrate ad libitum 3.6 5.5

Interval to first mate, min.
Forage ad libitum 1.8 1.6
Concentrate ad libitum 9.4 9.1

Libido score
Forage ad libitum 5.2 5.5
Concentrate ad libitum 4.1 4.1

Total number of matings
Forage ad libitum 9 9
Concentrate ad Iibitum I


ad libitum

ad libitum


Hours observed, total b,c
Animal observations, total
Grazing observations


Hours observed, total b,c
Animal observations, total
Exercise observations

a Study involved 10 bulls in lot fed concentrates and 14 bulls in forage-fed lot.

b Observed from daylight (6:00 a.m.)
4, 5, and 6.

c Observed from daylight (6:00 a.m.)
4, 5, and 6.

to dark (7:45) for three consecutive days, September

to dark (7:45) for three consecutive days, September








- 18 -


The effects of two methods of feeding upon the potential reproductive
potency of beef bulls were studied during two phases, a 196-day post-
weaning performance test followed by a 140-day continuation of the same
feeding regimen up to the usual sale age of commercial beef bulls.
One group of 14 fall-weaned bulls were self-fed a high energy concen-
trate diet offered ad libitum while-the other group was offered forage
(corn silage or fertilized Coastal Bermudagrass) ad libitum plus a
limited supplement of 7 or 8 lb. per day of the concentrate mixture.

Bulls fed concentrates ad libitum had a higher average daily gain
(2.48 lb.) than those fed forage ad libitum (2.05 Ib.) during Phase I
which ended in June. Average daily gains of both groups were lower
during Phase II which ended in October but the difference between groups
in average daily gain remained, being 1.95 and 1.46 lb. respectively
for the concentrate and forage fed groups. The difference in weight
gained by the two groups was visually evident in differing degrees of

A low incidence of digestive disorders, bloat and founder, was
observed in bulls fed concentrates ad libitum while none were observed
in those fed forage ad libitum.

A comparison of the average cost of feed per bull showed higher
costs of $35.80 and $60.77 during Phase I and II respectively for bulls
fed concentrates ad libitum.

Measures of grazing and non-grazing exercise revealed that bulls
fed forage ad libitum performed twice as much activity as those fed
concentrates ad libitum.

The various criteria showed semen quality to be slightly superior
for the group fed concentrates ad libitumn during Phase I but not appar-
ently different during Phase II until the last collection of semen
(approximately 22 to 25 months of age) when those fed forage ad libitum
displayed the highest quality.

High:environmental summer temperatures exerted an apparent inhib-
itory effect on sexual drive being most apparent in bulls fed concen-
trates ad libitum.

During studies of mating behavior and libido, 100% of bulls fed
forage ad libitum satisfactorily mated a heifer while only 10% of those
fed concentrates ad libitum were able to mount and mate.

- 19 -

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- 21

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