Heterogeneity of distribution for growth traits between Angus and Brahman backcross embryo transfer cattle

Abstract

Distribution of growth traits for [] Angus [] Brahman hics. and [] Brahman [] Angus (CC) embryo transfer calves was analyzed. Families (FC) (n=27) were created from backcross matings of Brahman and Angus purebred and F-1 crosses. Traits analyzed were birth weight (BW), weaning weight (WW), gain on grass (GG), feedlot average daily gain (FG), and slaughter weight (SW). Analyses of variance were performed using the procedures of SAS (1988) to determine differences between CC, family code nested within calf code (FC(CC)), SEX, birth year (BY), and birth season (BS). The analysis of variance indicated that calf code was a significant effect for GG (P < .0001), FG (P < 1 .0001), and SW (P < .0001). Family code nested within calf code was significant for all traits and SEX was significant for all traits excluding FG. Birth year and birth season were significant effects for WW, GG, FG, and SW. Classes set according to industry standards were BW (4 kg increments), WW (50 kg increments), GG (40 kg increments), FG (.40 kg increments), and SW (50 kg increments). Chi-square analysis was used to test for differences in distribution among the [] Angus [] Brahman and [] Brahman [] Angus cattle. Heterogeneity of distribution was found for steer and heifer GG (P < .001), steer and heifer FG (P < .001), steer SW (P < .005), and heifer SW (P < .001). The [] Angus [] Brahman cattle had the highest proportion of cattle with heavy birth and weaning weights, high gains on grass, high feedlot average daily gains, and heavy slaughter weights. Results indicated that the [] Angus [] Brahman and [] Brahman []Angus cattle should be treated as two different populations with respect to gain on grass, feedlot average daily gains, and slaughter weights. However, homogeneity of distribution was expressed for birth weight and weaning weight indicating similar variances among the [] Angus [] Brahman and [] Brahman [] Angus cattle.