J. Anim Sci.
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J. Anim Sci. 1988. 66:1236-1245.
© 1988 American Society of Animal Science
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Responsiveness of Bovine Corpora Lutea to Prostaglandin F2{alpha}:Comparison of Corpora Lutea Anticipated to Have Short or Normal Lifespans1

J. P. Copelin2, M. F. Smith2, H. A. Garverick3, R. S. Youngquist4, W. R. McVey, Jr.5 and E. K. Inskeep5

University of Missouri, Columbia 65211 and West Virginia University, Morgantown 26506

Abstract

The objective of this study was to determine if corpora lutea anticipated to have short lifespans were more responsive to the luteolytic action of prostaglandin F2{alpha} (PGF2{alpha}) than corpora lutea anticipated to have normal lifespans. Sixteen cows were allotted randomly to a hysterectomized-control (HC) or hysterectomized-progestogen (norgestomet) implant (HN) group. To verify that progestogen treatment of postpartum cows prior to induction of ovulation with gonadotropin-releasing hormone (GnRH) results in an increased number of cows exhibiting normal-length luteal phases, 21 additional cows were allotted randomly to a uterine intact-control (IC) or a uterine intact-progestogen implant (IN) group. Cows allotted to the HN and IN groups received norgestomet ear implants for 9 d beginning 17 to 21 d postcalving. All cows were injected (i.m.) with 100 µg GnRH 28 to 32 d postcalving (48 h after implant removal in the HN and IN groups) to induce ovulation. Two or 3 d after GnRH injection (d 0), cows in the HC (n = 8) and HN (n = 8) groups were hysterectomized to remove the major endogenous source of PGF2{alpha}, and on d 7 cows were injected (i.m.) with 10 mg PGF2{alpha} to assess luteal sensitivity. The proportion of corpora lutea having normal lifespans was greater (P < .1) for the IN than for the IC group. In HC and HN groups, concentration of progesterone (P) increased similarly from d 0 to 6. Injection of PGF2{alpha} in HC and HN groups on d 7 decreased (P < .01) concentration of P approximately 50% by 6 h after injection (similar for both groups). Complete luteolysis was induced by PGF2{alpha} in none of eight and two of eight cows in the HC and HN groups, respectively. In remaining cows (HC and HN groups) concentration of P increased (P < .01; similar for HC and HN groups) beginning 24 h after PGF2{alpha} and remained elevated through d 30 to 34 (end of experimental-period). In summary, corpora lutea anticipated to be short-lived were not more responsive to PGF2{alpha} than corpora lutea anticipated to have normal lifespans.

Footnotes

1 Contribution from the Missouri Agric. Exp. Sta. Journal Series No. 10361. This research was supported in part by USDA Grant No. 83-CRSR-2-2190 (West Virginia).

2 Dept. of Anim. Sci., Univ. of Missouri.

3 Dept. of Dairy Sci., Univ. of Missouri.

4 Dept. of Vet. Med. Surg., Univ. of Missouri.

5 Division of Anim. Sci., West Virginia Univ.






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Copyright © 1988 by the American Society of Animal Science.