Mimeo Series RCS 68-4 May!9uLj E LI0 .
OUR OBSERVATIONS WITH IMEENGESTRQL
ACETATE (MGA) FOR HSEIfRS-2/ 16 13
NIAY 18 1968
H. L. Chapman, Jr.-
S.A.S. Uni. of Fior: d
Melengestrol acetate (MGA) is a synthetic female hormbne-that---'--'
number of experiment stations have demonstrated to stimulate rate-of gain and
feed efficiency of feedlot heifers. The majority of earlier reports have
been with English-type heifers. The purpose of this experiment was to
determine if MGA affected growth, feed utilization or carcass characteristics
of crossbred heifers being fattened in drylot and.to determine if
diethylstilbestrol (DES) altered the effect.
Forty-five Brahman-crossbred heifers of approximately 10 months of age,
were divided into three equal groups on the basis of weight and quality and
allotted to the following experimental design:
Treatment
number Treatment description
1 Control
2 0.4 mg MGA/head/daily
3 0.4 mg MGA/head/day + 24 mg DES implanted at
the beginning of the experiment.
The experimental ration was comprised of 40% dried citrus pulp, -
27% hominy feed, 10% cottonseed meal (41%), 5% dehydrated' alfalfa
meal (17%), 15% cottonseed hulls, 1% urea-262, 1.5% dicalcium phosphate
and 0.5% trace mineralized salt. Vitamin A was added to the ration at
the level of 1,000 I.U. per pound of feed.
/ Presented at 1968 Beef Cattle Short Course, University of Florida.
SPhysiological studies were made by A. C. Warnick and carcass
evaluations by A. Z. Palmer and J. W. Carpenter.
2/ Grateful acknowledgement is made to TUCO Products Co., Division of
Upjohn Co., Kalamazoo, Michigan for their financial support of this
study.
_/ Animal Nutritionist and Head, Range Cattle Experiment Station.'
At the conclusion of a 151-day feeding period the heifers were
transported to Gainesville for carcass studies. The experimental
results are listed below:
Control
No. animals
Initial weight (lb)
Final weight (lb)
Total gain (lb)
Daily gain (lb)
Gainesville weight (lb)
Intransit shrink (%)1/
Percent hide
Warm carcass weight (lb)
Chilled carcass weight (lb)
Cooler shrink (%)
Dressing %2/
Li'ver weight (lb)
Percent liver
USDA grade
Fat over rib-eye (in)
Percent kidney
Rib-eye area (sq.in.)
Est. % yield
Right ovary wt. .(m).
Ni. active CL2/
Size largest follicle (mm)
Nop!. .follicles over 5 mm
Left ovary wt. (gm)
No.. active CL
Size largest follicle (mm)
No. follicles over, 5 mm
Uterine weights (gm)
Feed/lb gain
15.
480
799
319
2.11
764
4.6
8.7
479
470
1.9
61.49
11.2
1.5
G
0.33
3.4
&.84
S50.04
7.3
7
10.5
2.9
6.1
4
7.5
2.0
104.9
9.30
MGA MGA + DES
14
482
809
327
2.17
774
4.3
8.9
481
471
2.0
60.85
11.0
1.4
G
0.40
3.2
8.45
49.41
7.0
0
14.1
3.3
5.4
0
13.4
2.2
127.5
9.32
15
475
825
350
2.32
772
6.4
8.9
' 82
472
1.9
61.13
11.2
1.4
G .
0.35
3.1
.8.80
49.99
7.3
1
13.7
3.0
5.2
0
-9.5
2.5
131.6
8.72
1/ Intransit distance was 180 miles.
SDressing percent = chilled carcass weight
Gainesville weight
3/ CL = corpus luteum.
RCS68-4
750 copies
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Agricultural Sciences and should be
used only to trace the historic work of
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