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A Comparison of Estrous Cycle Synchronization Methods in Beef Cattle under Feedlot Conditions¹

Cornell University, Ithaca, New York

Abstract

Two trials involving 832 beef cows were conducted in the summers of 1963 and 1964. Satisfactory cycle synchronization was obtained in both years using MAP and CAP fed in liquid feed or in pellets. Feeding thyro-protein did not alter synchronization or subsequent fertility. Fertility at the synchronized estrus was higher in MAP-fed than in CAP-fed cows, and in the case of MAP-fed cows approximated that obtained in normal controls.

Fertility with natural or artificial breeding did not differ significantly. Fertility was uniformly high at the estrus subsequent to synchronization.

Feeding additional nutrients in the form of 1.63 to 1.86 kg. of pelleted concentrate feed for 18 days did not result in a significant increase in conception rate at first service.

Oxytocin injected at the time of artificial breeding caused a reduction in conception rate that approached significance. The conception rate was significantly lower for cows from which a calf had recently been weaned than for nonlactating cows.

¹ Supported in part by funds provided by Regional Research Project NE-41, Endocrine Factors Affecting Reproduction in Dairy Cattle, a cooperative study by Agricultural Experiment Stations in the Northeast and the Dairy Husbandry Research Branch, ARS, U.S.D.A. The financial support of the New York Artificial Breeders' Cooperative, The National Association of Animal Breeders, The Syntex Corp., Eli Lilly and Co., and The Upjohn Co. is also gratefully acknowledged. The cooperation of Briarcliff Farms, Inc., and the technical assistance of Richard Newman and Paul Goetchius is gratefully acknowledged.

² Present address: Cunningham Laboratory, Division of Animal Physiology, C.S.I.R.O., St. Lucia, Brisbane, Australia.

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				J. W. Lauderdale ASAS Centennial Paper: Contributions in the Journal of Animal Science to the development of protocols for breeding management of cattle through synchronization of estrus and ovulation J Anim Sci, February 1, 2009; 87(2): 801 - 812. [Abstract] [Full Text] [PDF]