J. Anim Sci.
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J. Anim Sci. 1973. 37:985-989.
© 1973 American Society of Animal Science
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Endocrine Response after GnRH in Luteal Phase Cows and Cows with Ovarian Follicular Cysts1, 2,

Roger J. Kittok, Jack H. Britt and Edward M. Convey

Michigan State University, East Lansing 48823

Abstract

Luteinizing hormone (LH) and progesterone were assayed in blood sera collected before and after gonadotropin releasing hormone (GnRH) administration (iv) to nine Holstein cows, five of which had ovarian follicular cysts. The four remaining cows were treated on day 10, 11 or 13 of the estrous cycle. GnRH was given in three doses of 100 µg each, at 120-min. intervals. Serum LH (ng/ml) in cows with ovarian follicular cysts was 1.2±0.3, 23.8±7.5, 14.3±2.8 and 4.7±1.2 at 0, 120, 240 and 360 min. after GnRH administration, respectively, compared to concentrations of 0.5±0.1, 5.9±0.9, 7.2±1.2 and 2.9±0.5, respectively, for luteal phase cows (P < .01). Peak LH occurred at 170 min. (33.9±6.6 ng/ml) in cystic cows and 145 min (17.3±2.4) in luteal cows. The change in LH concentration after each injection of GnRH was greater (P < .01) in cows with follicular cysts. Serum progesterone (ng/ml) increased from 0.9±0.4 at 0 min. to 2.0±1.2 at 20 min. in cystic cows, but this response was due to increased serum progesterone in two animals. Similarly, progesterone increased (P < .05) from 5.9±0.8 at 0 min. to 10.3±0.9 and 8.2±1.0 at 260 and 360 min., respectively, in luteal phase cows. Serum progesterone was 3.6±1.4 on day 11 after GnRH administration in cows with ovarian follicular cysts although only one cow had a palpable corpus luteum. All of the cows with follicular cysts exhibited estrus 20 to 24 days after GnRH treatment. Serum estradiol and estrone (pg/ml) prior to GnRH treatment for cows with follicular cysts averaged 9.4±3.1 and 3.8±0.5, respectively, which was not different from the means for cows treated during the luteal phase (8.8±0.7 and 3.0±0.4, respectively). Administration of repeated doses of GnRH produced a LH response similar to the preovulatory surge in the bovine and initiated estrous cycles in cows with ovarian follicular cysts.

Footnotes

1 Published with the approval of the director of the Michigan Agriculture Experiment Station as Journal Article No. 6259. This research was supported in part by NIH-Biomedical Science Support Grant allocation to the College of Agriculture and Natural Resources, No. 5-S05-RR0749-07. These data were presented in part at the Midwestern Section of the American Society of Animal Science, November 24 and 25, 1972, Chicago, Illinois. The authors wish to acknowledge the assistance of Drs. D. A. Morrow and B. Seguin for assistance in diagnosing ovarian follicular cysts in the cows in this study.

2 Animal Reproduction Laboratory, Department of Dairy Science.






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