J. Anim Sci.
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J. Anim Sci. 1985. 61:466-469.
© 1985 American Society of Animal Science
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A Seven-Day Synchronization Method for Ewes Using Medroxyprogesterone Acetate (MAP) and Prostaglandin F2{alpha}

J. A. Fitzgerald1,2,3,, A. J. Ruggles4, J. N. Stellflug1 and W. Hansel4

U.S. Department of Agriculture and Cornell University,4, Ithaca, NY 14853

Abstract

Estrous cycles of adult (n=27), farm-flock, Suffolk ewes and Polypay range ewes (n=224) were controlled with medroxyprogesterone acetate (MAP)-impregnated vaginal pessaries inserted (d 0) for 7 d in combination with prostaglandin F2{alpha} (PGF2{alpha}) injected on d 6. Descriptive criteria of the effects of this treatment regimen on endocrine characteristics of the estrous cycle were evaluated in the experiment with farm-flock ewes. The efficacy of this synchronization regimen on reproductive performance of range-bred ewes was tested in a second trial. Suffolk ewes were bred at the second observed estrus after treatment to provide comparisons of cycle length between treated and control ewes. Polypay ewes were exposed to fertile rams at the controlled estrus. Eighty-nine percent of Suffolk ewes were in estrus within 3 d after pessary removal. All nonsynchronized Suffolk ewes (n=24) were in estrus over a 21-d period. Estrous cycle lengths of treated ewes averaged 16.8 ± .2 d. Plasma progesterone concentrations were similar for treated and control ewes during the luteal phase of the estrous cycle. Ninety-one percent of the range-bred, controlled ewes lambed. Sixty-two percent of these ewes lambed within 150 d after exposure to fertile rams compared with only 17% of nonsynchronized ewes (P<.05). Lambing percentage was similar by 167 d for treated (87%) or control (88%) ewes. Lambs per ewe exposed averaged 1.68 and 1.80 for treated and nonsynchronized groups, respectively. These data indicate the effectiveness of this 7-d treatment method for control of the estrous cycle of ewes during the normal breeding season. Results further show that this treatment scheme has practical application for range breeding of ewes.

Footnotes

1 Present address: Western Region, Agricultural Research Service, USDA, U.S. Sheep Exp. Sta., Dubois, ID 83423.

2 Reprint requests: Agricultural Research Service, USDA, U.S. Sheep Exp. Sta., Dubois, ID 83423.

3 The technical assistance of W. G. Gardner, J. P. Miller, H. Frederiksen and D. Willes is gratefully appreciated. The secretarial help of Sue Hawk, Helen Dormady, Pat Wells and Vicki Gunter is also acknowledged. Mention of trade names of companies does not constitute an implied warranty by USDA or the authors. A portion of these data presented at the Amer. Soc. of Anim. Sci. Annu. Meet., Columbia, MO, August 7–10, 1984.

4 Dept. of Physiol., New York State College of Vet. Med.






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Copyright © 1985 by the American Society of Animal Science.