Escore de condição corporal de vacas da raça Nelore e suas relações com características de tamanho e reprodução

The aim of this study was to investigate the relationship of measures of body condition score (ECC) with mature size and reproduction traits in Nelore cows to support the possible use of ECC in breeding programs. Records used were repeated observations of ECC, body weight, hip height, days to calving and calving success rate, from 1931 Nelore cows belonging to a selection experiment established since 1978 at the Sertaozinho Experiment Station in Sao Paulo State, Brasil. Significant differences occurred among ECC classes for weight, days to calving and calving success, but not for hip height. The variance components were estimated by Bayesian inference using Gibbs sampling. ECC heritability and repeatability estimates (posterior means) were 0.21±0.03 and 0.29±0.02, respectively. Genetic correlation estimates (poste- rior means) between ECC and weight, hip height and days to calving were 0.37±0.09, -0.15±0.10 and -0.35±0.07, respectively. The posterior distribution chain of genetic correlation between ECC and calving success failed to reach convergence. Cows with higher ECC presented higher weight, fewer days to calving and higher calving success, but did not show differences with respect to hip height. Genetic correlation between ECC and days to calving is moderate and favorable, supporting the inclusion of this trait, together with cow reproduction traits, into a selection index to improve fertility of beef herds.