Body condition score of Nelore cows and its relation with mature size and gestation length

Abstract

The objective of this study was to evaluate the genetic variability of body condition score (BCS) in Nelore cows, and analyze its genetic correlations with mature weight (MW), mature height (MH) and gestation length (GL), in order to obtain information supporting the possible use of this score in breeding programs. The BCS was recorded on pregnancy diagnosis and ranged from 1 (very thin) to 5 (extremely fat). Adjusted means for MW, MH and GL according to the BCS classes were obtained using an univariate mixed model for each trait. Bayesian Inference using Gibbs Sampling was applied to estimate (co)variances components and genetic and phenotypic correlations, in two-trait analyses, considering a threshold animal model for BCS and a linear animal model for the other traits. Adjusted means for MW, MH and GL showed significant variation (p<0.0001) among BCS classes, indicating that cows with higher BCS have greater mature size, assessed by MW and MH measures, and longer GL than those with lower BCS. The BCS showed genetic variability, with posterior mean heritability of 0.23±0.05. Genetic correlations between the BCS with MW, MH and GL were 0.41±0.04; −0.06±0.03 and 0.10±0.02, respectively. Selection based on BCS should result in gain for body condition and, by indirect response, in changes in the same direction for cows MW. However, selection for BCS has little or no effect on MH and GL. So that BCS can effectively be used as a selection criterion of beef cows, further studies should be performed in order to obtain genetic associations with other economic traits.