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

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. Copyright © 1966. American Society of Animal Science . Copyright 1966 by American Society of Animal Science