Genotype × Environment Interactions Involving Proportion of Brahman Breeding and Season of Birth. II. Postweaning Growth, Sexual Development and Reproductive Performance of Heifers

Abstract

Postweaning growth, sexual development and reproductive traits were evaluated over a 3-yr period on 201 spring-born and 180 fall-born crossbred heifers with 0, 1/4 or 1/2 Brahman breeding. The proportion of Brahman breeding × season of birth interaction was significant for five traits (average daily gain weaning to yearling, yearling condition score, percentage of heifers detected in estrus, prebreeding condition score and percentage of heifers that became pregnant) and was not significant for six traits (yearling weight, hip height and conformation score, age and weight at puberty and prebreeding weight. Among spring-born heifers, 1/4 and 1/2 Brahman heifers out-gained (P<.05) 0 Brahman heifers from weaning to yearling by 50 and 66 g/d, respectively; among fall-born heifers, 1/4 and 1/2 Brahman heifers outgained (P<.05) 0 Brahman heifers by 41 and 104 g/d, respectively. Yearling weight of 1/2 Brahman heifers was 13 and 10 kg heavier (P<.05), respectively, than 0 and 1/4 Brahman heifers. Yearling hip height of 1/4 and 1/2 Brahman heifers were 1.9 and 5.7 cm taller (P<.05), respectively, than 0 Brahman heifers. Weight prior to the start of the breeding season were similar among crossbred heifer groups and spring-born heifers were 66 kg heavier (P<.05) than fall-born heifers. The percentage of heifers that became pregnant was similar among spring-born crossbred heifer groups, whereas among fall-born heifer groups 1/4 and 1/2 Brahman heifers were 25.2 and 49.4 percentage points lower (P<-05), respectively, than 0 Brahman heifers. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science.