J. Anim Sci.
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J. Anim Sci. 1967. 26:549-552.
© 1967 American Society of Animal Science
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Synchronization of Estrus in the Guinea Pig With 6a-Methyl-17a-Acetoxyprogesterone and the Effect on Subsequent Fertility

F. J. Karsch1 and B. R. Poulton

University of Maine, Orono2

Abstract

Inhibition and synchronization of estrus with MAP and with a combined treatment of MAP, PMS and HCG, and the subsequent effect on fertility were studied using 87 guinea pigs. Cycle inhibition was obtained in animals given 0.50 and 0.25 mg. of MAP per day. Synchronization of estrus was satisfactory in animals given these levels of the progestin for 20 days. The average deviation of the occurrence of estrus from the target point (5.0 days following MAP withdrawal) was 0.7 days for guinea pigs given 0.50 mg. of MAP and 1.4 days for those given 0.25 mg. The fertility of the animals bred during the first estrus following MAP at levels of 0.50 and 0.25 mg. was 69% and 92%, respectively; that of the controls was 75%. These MAP treatments had little effect on prolificacy.

Estrus was not synchronized satisfactorily when 50 I.U. of PMS and 25 I.U. of HCG were given intramuscularly following MAP withdrawal. Many of the animals injected with gonadotrophins did not come into estrus during the first 16 days post-treatment. The fertility of these guinea pigs was low, 20% for the animals given 0.50 mg. of MAP plus gonadotrophins and 40% for those given 0.25 mg. of MAP plus gonadotrophins.

Footnotes

1 Present address: Department of Animal Science, University of Illinois, Urbana, Illinois.

2 Department of Animal Sciences.

3 The authors wish to thank R. G. Zimbleman of the Upjohn Company, Kalamazoo, Michigan, for providing the 6a-methyl-17a-acetoxyprogesterone.






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Copyright © 1967 by the American Society of Animal Science.