Reproductive Behavior of Bos Indicus Females in a Subtropical Environment. IV. Length of Estrous Cycle, duration of Estrus, Time of Ovulation, Fertilization and Embryo Survival in Grade Brahman Heifers

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Abstract
Anderson (1944) reported an average estrous cycle length of 22 and 23 days, respectively, for European x Zebu and purebred Zebu cattle. The average duration of estrus was 7.4 and 4.8 hr., respectively. Other workers (Clamohoy, 1952; Rollinson, 1955; Villacorta, 1960) using small numbers of Zebu cattle found estrus to be longer than that reported by Anderson (1944) but shorter than that given in the literature for Bos taurus cattle in the temperate zone. A seasonal influence on reproductive performance was reported by Wilson (1946). The highest frequency of conception for 17,000 Zebu cows with year-round breeding in Nyassaland was found to be during the hottest months of October and November. Seasonal variations in lengths of estrus and the estrous cycle were observed by Hammond (1927) and Anderson (1944). The purpose of the present study was to determine length and regularity of the estrous cycle, duration of estrus and time of ovulation in relation to season as well as to obtain data on fertilization rate and embryo survival in grade Brahman heifers. Copyright © 1970. American Society of Animal Science . Copyright 1970 by American Society of Animal Science

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