Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: July 2, 2002
Publication Date: July 1, 2002
Technical Abstract: Genetic parameters were estimated for Brahman calf birth vigor and calf survival to weaning (n = 689) using animal and sire models. Calves were sired by 22 Brahman bulls and were born from 1995 to 1999. Birth vigor was subjectively assessed and evaluated as a binary character: calves with adequate vigor at birth were assigned 1 and those without adequate vigor were assigned 0. Calf survival to weaning was also evaluated as a binary trait: calves that survived to weaning were assigned 1, those that did not were assigned 0. Animal and sire models were used to estimate direct and maternal heritabilities. Calf gender and dam age were model fixed effects. Genetic correlations were estimated from sire models. Direct heritability estimates from sire models were 0.11 and 0.04, for birth vigor and calf survival, respectively. Direct and maternal heritability estimates from animal models were 0.11 and 0.12 for calf birth vigor, and 0.05 and 0.14 for calf survival to weaning. Transformation of these estimates to approximate the normal scale only slightly changed some, but not all, estimates. The estimated genetic correlation between birth vigor and birth weight was 0.14 (P < 0.001); genetic correlations were similarly low for birth vigor and weaning weight, weaning height, and weaning condition score. The estimated genetic correlations between calf survival to weaning and these characters were also low. However, there was an estimated genetic correlation between birth vigor and survival to weaning of 0.77 (P < 0.001). Although lowly heritable, there may be some value for calf birth vigor as an indicator trait for survival to weaning. Both animal and sire models produced similar direct heritability estimates, and sire rank (of EBVs or random solutions) changes for the two methods were minimal.