• TABLE OF CONTENTS
HIDE
 Front Cover
 Table of Contents
 Introduction
 Results of cattle pregnancy...
 Suggested methods for the improvement...
 2 examples where good management...
 Summary and recommendations
 Literature cited
 Back Cover














Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 623
Title: Factors influencing pregnancy rate in Florida beef cattle
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Permanent Link: http://ufdc.ufl.edu/UF00027642/00001
 Material Information
Title: Factors influencing pregnancy rate in Florida beef cattle
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 623
Physical Description: Book
Language: English
Creator: Warnick, A. C.
Meade, J. H. Jr.
Koger, M.
Publisher: University of Florida Agricultural Experiment Station
Publication Date: 1960
 Record Information
Bibliographic ID: UF00027642
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Table of Contents
        Page 2
    Introduction
        Page 3
    Results of cattle pregnancy survey
        Page 3
        Page 4
        Page 5
        Page 6
    Suggested methods for the improvement of reproduction
        Page 7
        Page 8
    2 examples where good management and proper culling practices helped increase production
        Page 9
    Summary and recommendations
        Page 9
    Literature cited
        Page 10
        Page 11
    Back Cover
        Page 12
Full Text


Bulletin 623


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
J. R. BECKENBACH, Director
GAINESVILLE, FLORIDA











Factors Influencing Pregnancy Rate

In Florida Beef Cattle


A. C. WARNICK, J. H. MEADE, JR., and M. KOGER



















Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


July 1960
























CONTENTS
Page

INTRODUCTION ............... 3
INTRODUCTION --------------- -------------------- 3

RESULTS OF PREGNANCY SURVEY ............... -------------.--- .. ------- 3
Procedure .............-3
Procedure .----------------------- -------------------- 3

Effect of Age of Dam and Lactation Status .............------------------ 4

Effect of Breed ...................-.- -------- 5

Effect of Year .............. .......-..... -- 6

Effect of Location .................. .. ......- ...... -------- 6

SUGGESTED METHODS FOR IMPROVEMENT OF REPRODUCTION

Pregnancy Diagnosis -........ ......--.-.....-------- 7

Bull Care ......... 8
Bu lC r ---------- ------ -------------------------- ------ ----~---- 8~~~~~~

General Management -............... ..... .... -- --------------. -- 8

EXAMPLES OF GOOD MANAGEMENT AND CULLING ...------------------..-------- 9

SUMMARY AND RECOMMENDATIONS ...........----------------------.- 9

LITERATURE CITED ......-------.- -..-..-.-. ----- 10








Factors Influencing Pregnancy Rate

In Florida Beef Cattle

A. C. WARNICK, J. H. MEADE, JR., and M. KOGER 1

INTRODUCTION
One of the basic prerequisites of a profitable beef cattle oper-
ation is a high rate of reproduction. This fact has been recog-
nized by cattlemen for years and today its importance should
not be overlooked when methods are sought to improve a cattle
operation. Although there are many other factors that affect
economic returns, the fact remains that in a cow-and-calf type
enterprise, if there is no calf there is no return.
Today, Florida is in the unique position of being able to in-
crease its calving percentage more than any other state in the
nation. In 1956 the United States Department of Agriculture
estimated that the calf crop in Florida was only 68 percent,
which was the lowest of any state. At the same time the average
calf crop of the Southeastern states was 81 percent, while the
average for the United States was 87 percent.
Without increasing the number of brood cows, Florida could
produce 71,000 more calves annually by increasing its calving
percentage to the average of the Southeastern states. By increas-
ing the calf crop to the average of that for the entire United
States, Florida would increase its production by 105,000 calves
annually. This would mean approximately 84,000,000 more net
profit annually to the cattle producers in Florida.
It is the purpose of this report to: (1) Make cattlemen more
aware of the low rate of reproduction in Florida beef cattle by
discussing the results of a pregnancy survey; and (2) suggest
methods for improving the calving percentage.

RESULTS OF CATTLE PREGNANCY SURVEY
Procedure.-Since it was known that the calving percentage
in Florida was very low, a pregnancy survey was initiated in
1953 by the Department of Animal Husbandry and Nutrition to
study the rate of reproduction in Florida beef cattle. This study
covered the 5-year period from 1953 through 1957. It included
10,170 cattle from both Experiment Station herds and private


'Department of Animal Husbandry and Nutrition.








Factors Influencing Pregnancy Rate

In Florida Beef Cattle

A. C. WARNICK, J. H. MEADE, JR., and M. KOGER 1

INTRODUCTION
One of the basic prerequisites of a profitable beef cattle oper-
ation is a high rate of reproduction. This fact has been recog-
nized by cattlemen for years and today its importance should
not be overlooked when methods are sought to improve a cattle
operation. Although there are many other factors that affect
economic returns, the fact remains that in a cow-and-calf type
enterprise, if there is no calf there is no return.
Today, Florida is in the unique position of being able to in-
crease its calving percentage more than any other state in the
nation. In 1956 the United States Department of Agriculture
estimated that the calf crop in Florida was only 68 percent,
which was the lowest of any state. At the same time the average
calf crop of the Southeastern states was 81 percent, while the
average for the United States was 87 percent.
Without increasing the number of brood cows, Florida could
produce 71,000 more calves annually by increasing its calving
percentage to the average of the Southeastern states. By increas-
ing the calf crop to the average of that for the entire United
States, Florida would increase its production by 105,000 calves
annually. This would mean approximately 84,000,000 more net
profit annually to the cattle producers in Florida.
It is the purpose of this report to: (1) Make cattlemen more
aware of the low rate of reproduction in Florida beef cattle by
discussing the results of a pregnancy survey; and (2) suggest
methods for improving the calving percentage.

RESULTS OF CATTLE PREGNANCY SURVEY
Procedure.-Since it was known that the calving percentage
in Florida was very low, a pregnancy survey was initiated in
1953 by the Department of Animal Husbandry and Nutrition to
study the rate of reproduction in Florida beef cattle. This study
covered the 5-year period from 1953 through 1957. It included
10,170 cattle from both Experiment Station herds and private


'Department of Animal Husbandry and Nutrition.






Florida Agricultural Experiment Stations


herds throughout the state. Pregnancy was determined by
rectal palpation 3 or more months after the end of the breeding
season. The data were classified by age of dam, lactation status
of the cow during the breeding season, breed of cow, year and
ranch or location. The effects of these factors on pregnancy
rate were determined by the method of least squares as outlined
by Anderson and Bancroft (1) and Chew (2). The overall preg-
nancy rate was 70.9 percent.
Effect of Age of Dam and Lactation Status on Pregnancy
Rate.-Previous work in Florida has shown that both age of
cow and whether or not the cow is nursing a calf during the
breeding season influences her ability to settle or become preg-
nant. In this study, cows were grouped on the basis of age and
lactation status as follows: non-lactating 2-year-old heifers, non-
lactating 3-year-old cows, lactating 3-year-old cows, non-lactating
cows 4 years old or older and lactating cows 4 years old or older.
The results are shown in Table 1.

TABLE 1.-EFFECT OF AGE OF DAM AND LACTATION STATUS ON
PREGNANCY RATE.
Number Deviation Adjusted
Age of Dam Lactation of from Pregnancy
Status Females Standardt- Rate

Years Percent Percent
2 ............. Non-lactating-. 2,287 3.5** 68.7
3 .... ...-..- Non-lactating_ 303 10.6** 75.8
3 ......... Lactating .... 812 -15.5** 49.7
4 or more .. Non-lactating. 2,938 29.9** 95.1
4 or more ..... Lactating ...... 3,830 0 65.2

Overall Average 10,170 ...70.9

** Significantly different from standard at 0.01 level of probability.
f Four years or older lactating cows were used as standard in this study. Residual
mean square was used as an error term in all analyses. Mean was used as a base for adjusted
rates in all analyses.

All of the age of dam and lactation status groups were sig-
nificantly different from the standard (lactating cows 4 years
old or older). The highest pregnancy rate of 95.1 percent was
found in the non-lactating cows 4 years old or older while the
lowest pregnancy rate, 49.7 percent, was in the lactating 3-year-
old cows.







Factors In i, ;,. -I Pregnancy Rate in Florida Beef Cattle 5

It is interesting to note the difference between lactating and
non-lactating cows of the same age. The non-lactating 3-year-
old cows had a 26.1 percent higher pregnancy rate than the
lactating 3-year-old cows and the non-lactating cows 4 years old
or older had a 29.9 percent higher pregnancy rate than the lac-
tating cows 4 years old or older. This shows that the stress of
lactation decreases the ability of many Florida cows to conceive.
This means (1) they may need extra feed or (2) genetically they
are poor reproducers and thus need to be culled if feed and other
management factors are adequate. These data also show that
the lowest reproduction rate is obtained with the 3-year-old
heifer which is nursing a calf.
Effect of Breed on Pregnancy Rate.-There were 7 different
breed groups included in this study. They were British, Brah-
man, Santa Gertrudis, Brangus, British X Native, Brahman X
Native and Brahman X British. The differences in pregnancy
rates among breeds are presented in Table 2.

TABLE 2.-EFFECT OF BREED ON PREGNANCY RATE.
Deviation Adjusted
Breed of Cow Number of from Pregnancy
Females Standardt Rate
Percent Percent
British ............. .. ...... 3,461 0 78.7
Brahman 2...................... 256 15.8** 62.9
Santa Gertrudis ............... 320 -15.2* 63.5
Brangus ................................ 270 7.4* 71.3
British X Native .......... 486 4.6 83.3
Brahman X Native ......... 4,814 -12.7** 66.0
Brahman X British ............ 563 8.0" 70.7

Overall Average -.. ..... 10,170 70.9

** Significantly different from standard at 0.01 level of probability.
Significantly different from standard at 0.05 level of probability.
7 British cows were used as standard in this study.

All of the breed groups were significantly lower in reproduc-
tive rate than the British group except the British X Native
group, which was slightly higher. The British X Native group






Florida Agricultural Experiment Stations


had a pregnancy rate of 83.3 percent while the Brahman group
was the lowest with 62.9 percent.
Cows classified as a mixture of British and Native breeding
had a 17.3 percent higher pregnancy rate than Brahman X Native
cows. In general, the cattle that were predominantly of British
breeding had a higher rate of reproduction than the cattle that
were predominantly of Brahman breeding. Thus, more emphasis
needs to be placed on culling for low reproduction on Brahman
and Brahman crossbred cattle.
Effect of Year on Pregnancy Rate.-The 5 years from 1953
through 1957 were included in this study. The deviations in
pregnancy rate due to years are shown in Table 3.

TABLE 3.-EFFECT OF YEAR ON PREGNANCY RATE.
I Deviation Adjusted
Year Number of from Pregnancy
Females Standardt Rate

Percent Percent
1953 .............. 759 8.9** 66.8
1954 ............. 1,863 -10.9** 64.8
1955 ............. 1,465 8.1** 67.6
1956 ........._ 4,746 0 75.7
1957 ............- 1,337 3.8* 79.6

Overall Average ............... 10,170 ... 70.9

** Significantly different from standard at 0.01 level of probability.
Significantly different from standard at 0.05 level of probability.
t The year 1956 was used as standard in this study.

The pregnancy percentages in 1953, 1954 and 1955 were sig-
nificantly lower than in 1956, while the pregnancy percentage
in 1957 was significantly higher than in 1956. Possibly the calf
crop is increasing in Florida as better production practices are
being used.
Effect of Location on Pregnancy Rate.-The variations in
pregnancy rate among the 18 different locations were large. The
effects of the different locations are given in Table 4.
The range in pregnancy rate at the different locations was
from 47.9 to 88.9 percent. In general, the Experiment Station
herds had a higher average pregnancy rate than the ranches.
This would indicate that calf crops can be increased in Florida







Factors If.,l.i, ,, ', Pregnancy Rate in Florida Beef Cattle 7

to high levels provided good feeding, breeding and management
practices are used.

TABLE 4.-EFFECT OF LOCATION ON PREGNANCY RATE.

Location Number of Females Adjusted
Pregnancy Rate

Experiment Stations Percent

E 1 ................................ .... 614 86.57
E 2 .......... ........... ............344 82.56
E 3 ................................ .... 283 87.11
E 4 ............................. 867 80.62
E 5 .................................... 577 80.43
Ranches
R 1 .......... ......................... 422 83.94
R 2 .................... ............. 1,233 80.35
R 3 ................ ... .... 107 59.73
R 4 ...................................... 801 54.44
R 5 ...................................... 182 82.95
R 6 ............................. ............ 999 47.92
R 7 ............................. 408 72.77
R 8 ........................................ 922 64.67
R 9 .. ................................. 190 55.05
R 10 .................... ........ ... 728 60.73
R 11 ......................... ..... .. 1,153 88.87
R 12 .. ........... .....................154 58.42
R 13 .... ....... ... ..... ... 186 49.24


Overall Average ........._ 10,170 70.91


SUGGESTED METHODS FOR THE IMPROVEMENT
OF REPRODUCTION

Many factors influence the rate of reproduction in beef cattle.
A thorough knowledge of some of these factors should enable
the livestock producer to raise the level of reproduction in his
herd and therefore have a more profitable operation. The follow-
ing suggestions are stated briefly with the hope that they may
aid livestock producers in increasing the rate of reproduction in
their herds.
1. Pregnancy Diagnosis Can Help.-By checking cows for
pregnancy at 2 to 4 months after the end of the breeding season
a rancher knows which cows will produce a calf the next year
and which will not. The non-pregnant cows should be marked
and separated from the pregnant ones. These non-pregnant
cows should be sold, and this can be done when they are still
grass fat and can bring a good return. This will eliminate the






Florida Agricultural Experiment Stations


cows that do not calve regularly and will also save the cost of
wintering a cow that is not going to produce a calf for at least 17
or 18 months. If for some reason the dry cows are kept, they
should be kept separate from the remainder of the herd so that
the best feed and care can be given to the cows that are going
to produce a calf.
Pregnancy diagnosis is performed by the rectal method in
which the uterus and fetus are felt through the rectal wall.
This method is very accurate when performed by a qualified
person. It is rapid and 1 person may examine 500 to 900 cows
in a day. It can be done without too much additional labor
when cows are being handled for other reasons, such as drench-
ing, weaning and branding.
2. Bull Care.-Since each bull produces a number of offspring
he should be given special attention. He should be in good breed-
ing condition (but not excessively fat) before he is put in with
the cows during the breeding season. Where it is possible he
should be given supplemental feed during the breeding season.
Just prior to the breeding season his semen should be checked
to insure that he has a high concentration of motile sperm. This
should be done again about the middle of the breeding season.
Bulls with low quality semen should be culled. Any competent
veterinarian can perform this semen examination.
Each bull should have sound feet and legs and the ability to
travel over the pasture so that he can mate with the cows. Care
should be taken not to mate young bulls with too many cows.
There should be enough fertile bulls for the number of cows in
the herd, which is usually one bull for each 25 cows. It is much
better to have an extra bull or two rather than not enough.
Also, bulls should be visually observed frequently during the
breeding season.
3. General Management Practices.-Good, sound beef cattle
management should be practiced at all times. Adequate nutri-
tion is necessary for a high rate of reproduction. In many cases
supplemental feeding is necessary to maintain the proper level
of protein in the ration throughout the year. Experimental
results have shown that low protein rations will keep cows from
showing estrus. Also, it has been shown that cattle on clover
pasture usually have a higher reproductive rate than cattle on
grass pasture.
Good records should be kept so that the non-producing cows
can be culled and replacement heifers saved from the best pro-






Factors Iufl.'r ,. .p.. : P, .,~.s. .,, Rate in Florida Beef Cattle 9

during cows in the herd. These replacement heifers should be
selected from cows that calve every year. If possible, they should
be kept separate the first year or two so they may be given
special care and supplemental feed when necessary. They should
weigh 800 pounds or more as they go into the breeding herd.
The length of the breeding season should be controlled. Gen-
erally, a 90- to 120-day breeding season is recommended. Also,
the calves should be weaned at the proper time (6 to 8 months)
and not left on their dams for an excessive time.
All cows that are brucellosis (Bang's) reactors should be
culled from the breeding herd. Vaccination of replacement
calves for Bang's disease should be a routine practice at 4 to
8 months of age.

2 EXAMPLES WHERE GOOD MANAGEMENT AND PROPER
CULLING PRACTICES HELPED INCREASE
REPRODUCTION
In a private herd of commercial cows in north Florida the
reproductive rate was 64 percent in 1956. During this year
most of the previously mentioned management practices were
initiated. The pregnancy rate increased to 73 percent in 1957
and 92 percent in 1958.
In an Experiment Station herd of commercial cows the preg-
nancy rate was 44 percent in 1953 and 55 percent in 1954. The
pregnancy rate in this herd increased to 82 percent in 1955,
86 percent in 1956, 88 percent in 1957 and 1958 and 92 percent
in 1959.
These 2 examples are typical of what can occur throughout
Florida by the application of good production practices.

SUMMARY AND RECOMMENDATIONS
1. The rate of reproduction in Florida beef cattle is too low.
2. Breed and lactation status both exert a significant influ-
ence on rate of reproduction.
3. Certain herds had a good reproduction rate indicating
an adequate reproduction rate can be achieved.
4. The following suggestions are offered for improving the
calving rate in Florida beef cattle.
a. Diagnose cows for pregnancy after the breeding season
and cull those that are not pregnant.






Factors Iufl.'r ,. .p.. : P, .,~.s. .,, Rate in Florida Beef Cattle 9

during cows in the herd. These replacement heifers should be
selected from cows that calve every year. If possible, they should
be kept separate the first year or two so they may be given
special care and supplemental feed when necessary. They should
weigh 800 pounds or more as they go into the breeding herd.
The length of the breeding season should be controlled. Gen-
erally, a 90- to 120-day breeding season is recommended. Also,
the calves should be weaned at the proper time (6 to 8 months)
and not left on their dams for an excessive time.
All cows that are brucellosis (Bang's) reactors should be
culled from the breeding herd. Vaccination of replacement
calves for Bang's disease should be a routine practice at 4 to
8 months of age.

2 EXAMPLES WHERE GOOD MANAGEMENT AND PROPER
CULLING PRACTICES HELPED INCREASE
REPRODUCTION
In a private herd of commercial cows in north Florida the
reproductive rate was 64 percent in 1956. During this year
most of the previously mentioned management practices were
initiated. The pregnancy rate increased to 73 percent in 1957
and 92 percent in 1958.
In an Experiment Station herd of commercial cows the preg-
nancy rate was 44 percent in 1953 and 55 percent in 1954. The
pregnancy rate in this herd increased to 82 percent in 1955,
86 percent in 1956, 88 percent in 1957 and 1958 and 92 percent
in 1959.
These 2 examples are typical of what can occur throughout
Florida by the application of good production practices.

SUMMARY AND RECOMMENDATIONS
1. The rate of reproduction in Florida beef cattle is too low.
2. Breed and lactation status both exert a significant influ-
ence on rate of reproduction.
3. Certain herds had a good reproduction rate indicating
an adequate reproduction rate can be achieved.
4. The following suggestions are offered for improving the
calving rate in Florida beef cattle.
a. Diagnose cows for pregnancy after the breeding season
and cull those that are not pregnant.






Florida Agricultural Experiment Stations


b. Have enough fertile bulls for the number of cows in the
herd. Have a veterinarian check the semen quality
of your bulls before and during the breeding season.
Cull bulls that are not fertile.
c. Be sure a proper level of protein and adequate feed is
maintained in the brood cow ration throughout the year.
d. Keep records and save replacement heifers from regular
producing dams which are weaning heavy calves of good
quality.
e. Breed cows in a 90- to 120-day breeding season and wean
calves at 6 to 8 months of age.
f. Sell all cows for slaughter that are brucellosis (Bang's)
reactors and vaccinate calves for brucellosis (Bang's
disease).
g. Use good, sound beef cattle management practices at all
times.
LITERATURE CITED
1. ANDERSON, R. L., and T. A. BANCROFT. Statistical Theory in Research.
McGraw-Hill Book Company, Inc. New York, New York. 1952.
2. CHEW, VICTOR. Experimental Designs in Industry. John Wiley and
Sons, Inc. New York, New York. 1958.








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