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 Beal, W. E. Articles by Corah, L. R. Search for Related Content PubMed PubMed Citation Articles by Beal, W. E. Articles by Corah, L. R.

Variation in Conception Rates Following Synchronization of Estrus with Melengestrol Acetate and Prostaglandin F₂¹

Virginia Polytechnic Institute and State University, Blacksburg 24061 , The Upjohn Company, Kalamazoo, MI 49001 , The Ohio State University, Columbus 43210 and Kansas State University, Manhattan 66506

Abstract

Beef cows and heifers (n = 263) at three locations that were exhibiting estrous cycles either were fed .5 mg/d melengestrol acetate (MGA) for 7 d and administered prostaglandin F₂ (25 mg, i.m.) on the last day of MGA feeding or were untreated. State of the estrous cycle at the beginning of the experiment was determined based on estrous detection and(or) progesterone concentrations in pretreatment blood samples. Estrous was checked twice daily for 30 d posttreatment. Animals were artificially inseminated approximately 12 h after detection of estrus. A synchronized estrus (< 7 d posttreatment) was detected in 72% of the treated animals. More animals in the treated group became pregnant during the first 7 d of breeding, but their conception rate was lower than that of animals in the control group (P < .05). Conception rate (36%) was reduced among treated animals when MGA feeding began late (d 14 to 20) in the estrous cycle. Conversely, the conception rate (66%) of treated animals fed MGA beginning earlier in the cycle was not different from that of control animals (73%; treatment x stage of cycle; P < .05).

¹ A portion of these data were presented at the annu. meet. of the Am. Soc. of Anim. Sci. in 1986 (Abstr. 473).

² Dept. of Anim. Sci., Virginia Polytechnic Institute and State University, Blacksburg 24061.

³ Reprod. and Growth Physiol. Unit. The Upjohn Co., Kalamazoo 49001.

⁴ Dept. Anim. Sci., The Ohio State University, Columbus 43210.

⁵ Anim. Sci. and Ind. Dept., Kansas State University, Manhattan 66506.

This article has been cited by other articles:

				A. M. Richardson, B. A. Hensley, T. J. Marple, S. K. Johnson, and J. S. Stevenson Characteristics of estrus before and after first insemination and fertility of heifers after synchronized estrus using GnRH, PGF2{alpha}, and progesterone J Anim Sci, November 1, 2002; 80(11): 2792 - 2800. [Abstract] [Full Text] [PDF]

				M. F. Martinez, J. P. Kastelic, G. P. Adams, and R. J. Mapletoft The use of a progesterone-releasing device (CIDR-B) or melengestrol acetate with GnRH, LH, or estradiol benzoate for fixed-time AI in beef heifers J Anim Sci, July 1, 2002; 80(7): 1746 - 1751. [Abstract] [Full Text] [PDF]