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 Google Scholar Google Scholar Articles by Short, R. E. Articles by Bellows, R. A. Search for Related Content PubMed PubMed Citation Articles by Short, R. E. Articles by Bellows, R. A.

Induced LH Release in Spayed Cows¹

U.S. Department of Agriculture, Montana Agricultural Experiment Station, Miles City 59301 and University of Manitoba, Winnipeg

Abstract

Experiment I. LH levels rose from 3.1 ng/ml in 10 cows on day 1 following ovariectomy to 6.8 on day 28 (b=0.122, P< .01). Eighteen cows were injected IM with 10 mg estradiol-17ß 25 days following ovariectomy. Nine were pretreated with 50 mg progesterone per day (IM) for 10 days from 14 to 25 days postovariectomy. Estrogen induced a significant LH release and estrus in all cows. Progesterone pretreatment had no effect on LH levels, acute LH release or expression of estrus.

Experiment II. Eighteen ovariectomized cows were given one IM injection of 10 mg estradiol-17ß. Six were given no other injections, six were injected with progesterone and six were injected with cortisol acetate. Twenty-five milligrams progesterone and 100 mg cortisol acetate were injected four times at 12-hr. intervals starting 12 hr. before the estrogen injection. Blood samples were taken by jugular venipuncture and estrus checked at –12 and 0 hr. from the estrogen injection and every 4 hr. from 12 to 40 hr. post-estrogen. All cows had an LH peak from 16 to 24 hr. post-estrogen injection. Progesterone or cortisol acetate treatment had no effect on interval to or height of LH peak. The proportion of cows detected in estrus was lower in progesterone-treated cows but the interval to estrus did not differ. Corticoid and estrogen levels were not affected by treatment but changed with time. Progestins decreased with time but progesterone-treated cows had elevated levels at 4 or 8 hr. after each progesterone injection.

¹ This study was a contribution to Western Regional Research Project W-112, Reproductive Performance in Beef Cattle. Publication has been approved by the Director of the Montana Agricultural Experiment Station, Journal Series No. 378.

² U. S. Range Livestock Experiment Station, A.R.S., Miles City, Montana.

³ Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada.

⁴ Montana Agricultural Experiment Station, Miles City, Montana.

⁵ Authors express appreciation to: Dr. G. D. Niswender, Colorado State University, for anti-bovine LH serum; Dr. L. E. Reichert, Jr., Emory University, for purified bovine LH; Dr. I. I. Geschwind, University of California, for anti-ovine LH serum; Dr. S, A. Tillson, Alza Corporation, Palo Alto, California, for anti-estrogen serum; Mrs. Janee Schmidt, Morris Krausz, Howard Traweek and Bill Wolf for technical assistance.