J. Anim Sci.
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J. Anim Sci. 1987. 64:782-789.
© 1987 American Society of Animal Science
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Hormone Secretion and Characteristics of Estrous Cycles after Treatment of Heifers with Human Chorionic Gonadotropin or Prostaglandin F2{alpha} during Corpus Luteum Formation1

S. D. Helmer and J. H. Britt2,3,

North Carolina State University4, Raleigh 27695-7621

Abstract

Fertility in cattle is related positively to concentrations of progesterone in blood during the estrous cycle preceding insemination. This study determined whether treatment of heifers with prostaglandin F2{alpha} (PGF2{alpha}) or human chorionic gonadotropin (hCG) during d 2 to 4 of an estrous cycle affected progesterone during that cycle and whether hormone secretion during the cycle and onset of subsequent estrus were related to progesterone secretion. Nine Holstein heifers were assigned to an experiment designed as a triplicate Latin square, and each heifer received each of three treatments during three consecutive estrous cycles. Treatments were: saline (control, 1 ml) on d 2, 3 and 4 after estrus; hCG, 1000 IU on d 2, 3 and 4; and PGF2{alpha}, 25 mg on d 3 with repeated doses 12 and 24 h later. Progesterone throughout the estrous cycle was higher in heifers given hCG than in those given saline. Progesterone during the first week of the cycle was lower in heifers given PGF2{alpha} than those given saline, but means for these two groups were similar thereafter. Number of peaks of 15-keto,13,14-dihydro-PGF2{alpha} (PGFM) during 24 h after onset of luteolysis was lower in heifers given hCG than in those given saline or PGF2{alpha}. Patterns of secretion of luteinizing hormone and estradiol at subsequent estrus were not affected by treatment. Temporal relationships among hormone secretion and onset of estrus were unaffected by treatment.

Footnotes

1 Paper no. 9434 of the Journal Series of the North Carolina Agr. Res. Ser., Raleigh, NC 27695-7621. The use of trade names in this publication does not imply endorsement by the North Carolina Agr. Res. Ser. of the product named, nor criticism of similar ones not mentioned.

2 Address reprint requests to this author.

3 K. T. Kirton, The Upjohn Co., Kalamazoo, MI provided antiserum against PGFM. Antiserum against bovine LH was provided by T. E. Kiser, Univ. of Georgia. Antiserum against estradiol-17ß was provided by N. R. Mason, Eli Lilly, Greenfield, IN. Purified bovine LH (LER 1716-2) was provided by L. E. Reichert, Jr., Albany Medical College, Albany, NY. Care of animals was provided by J. Johnson. Excellent laboratory assistance was provided by R. Mason and V. Hedgpeth. K. Heller and J. D. Armstrong provided assistance in collecting blood samples. S. Mizelle provided excellent help in typing the manuscript.

4 Dept. of Anim. Sci., Box 7621.






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Copyright © 1987 by the American Society of Animal Science.