J. Anim Sci.
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J. Anim Sci. 1975. 41:1394-1399.
© 1975 American Society of Animal Science
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Gonadotropin Induced Multiple Births in Beef Cows Following Estrus Synchronization1

M. R. Johnson2, E. J. Turman2 and D. F. Stephens3,4,

Oklahoma Agricultural Experiment Station, Stillwater 74074 and U. S. Department of Agriculture, El Reno 73036

Abstract

Sixty-five lactating multiparous beef cows were utilized to compare the effectiveness in inducing multiple births of a sequence of two PMSG injections timed from either a naturally occurring or a progestogen synchronized estrus. Estrus was synchronized by individually feeding CAP. All cows received subcutaneous injections of PMSG, 1,080 IU on day-5 and 1,440 IU on day-17 of the cycle, with an intravenous injection of 2,500 IU HCG given at time of mating or insemination.

Four treatments were imposed: treatment I — not estrus synchronized, breeding by natural service; treatment II — estrus synchronized, breeding by natural service; treatment III — estrus synchronized, breeding by artificial insemination at post-PMSG estrus; treatment IV — estrus synchronized, all cows bred by artificial insemination on days-3 and 4 post-PMSG.

Conception rate at first post-PMSG estrus was higher in treatment I than in treatment II (P<.05) or treatments III or IV (P<.01). The conception rate for the total 60 to 90 day breeding season was also lower in all estrus synchronized groups.

Footnotes

1 Journal Article 2945 of the Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma. Research conducted by the Department of Animal Sciences and Industry in cooperation with the U.S.D.A., Agricultural Research Service, Southern Region.

2 Department of Animal Sciences and Industry, Oklahoma State University, Stillwater.

3 Fort Reno Livestock Research Station, A.R.S., U.S.D.A. Present address: Department of Animal Science, University of Nebraska, Lincoln.

4 Authors express appreciation to Dr. J. F. Wagner, Eli Lilly Company, Greenfield, Indiana, for providing the PMSG, HCG and CAP used in this study.






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Copyright © 1975 by the American Society of Animal Science.