HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Spicer, L. J. Articles by Echternkamp, S. E. Search for Related Content PubMed PubMed Citation Articles by Spicer, L. J. Articles by Echternkamp, S. E.

Effects of Intermittent Injections of LHRH on Secretory Patterns of LH and FSH and Ovarian Follicular Growth During Postpartum Anovulation in Suckled Beef Cows^1,2,

Michigan State University^,7 East Lansing 48824 and U.S. Department of Agriculture^,6 Clay Center, NE 68933

Abstract

Changes in numbers of ovarian follicles and coincident secretion of pituitary gonadotropins were characterized in suckled, anovulatory beef cows injected iv with 500 ng of luteinizing hormone-releasing hormone (LHRH) every 2 h for 48 or 96 h, starting 21.4 ± .4 d after parturition. Two hours after the last injection, all cows were ovariectomized. Compared with saline-injected controls, LHRH had no effect on baseline or overall concentrations of luteinizing hormone (LH) in serum (P>.10), but increased (P<.05) frequency and decreased (P<.05) amplitude of LH pulses. Luteinizing hormone-releasing hormone increased (P<.05) baseline concentration of follicle stimulating hormone (FSH) in serum and frequency of FSH pulses, but decreased (P<.05) pulse amplitude. Overall concentrations of FSH increased 20% (P<.10). Exogenous LHRH did not affect diameter of the two largest follicles or numbers of follicles 1.0 to 3.9 mm, 4.0 to 7.9 mm or 8.0 mm in diameter. These data suggest that increasing the frequency of episodic LH and FSH pulses in postpartum cattle by intermittent administration of LHRH did not increase mean circulating levels of LH, or alter size and numbers of ovarian follicles within the 96-h period of injections. Thus, induction of ovulation in anovulatory cows treated with low-dose injections of LHRH cannot be explained on the basis of an increase in mean concentrations of LH or numbers of antral follicles within 96 h after initiation of injections.

¹ Michigan Agr. Exp. Sta. Journal Article No. 11695.

² We thank Steven Lyth, Lisa Ritchie, Margie McAlhany, Jinnie Stora and Jolene Urbauer for expert technical assistance; K. W. Cheng, Dept. of Physiol., Manitoba, Canada, for supplying bovine FSH and antisera; and the Natl. Pituitary Agency, NIAMDD, for supplying bovine LH.

³ Present address: M. S. Hershey Medical Center, Pennsylvania State Univ., Hershey, PA 17033.

⁴ Present address: Merck, Sharp and Dohme Res. Lab., Merck & Co., Inc., Rahway, NJ 07065.

⁵ To whom reprint requests should be addressed.

⁶ Roman L. Hruska U. S. Meat Anim. Res. Center.

⁷ Dept. of Anim. Sci.

This article has been cited by other articles:

				T. M. Prado, R. P. Wettemann, L. J. Spicer, J. A. Vizcarra, and G. L. Morgan Influence of exogenous gonadotropin-releasing hormone on ovarian function in beef cows after short- and long-term nutritionally induced anovulation J Anim Sci, December 1, 2002; 80(12): 3268 - 3276. [Abstract] [Full Text] [PDF]