GENETIC AND PHENOTYPIC ESTIMATES OF VISUAL SCORES AND AVERAGE DAILY GAIN FROM BIRTH TO WEANING OF CATTLE USED TO FORM THE BRANGUS BREED.

Abstract

The aims of this study were to estimate genetics parameters for visual scores of conformation (C), precocity (P) and musculature (M), measured at weaning and average daily gain from birth to weaning(GND) of animals used to form the Brangus breed, born from 1986 to 2002. Data was provided by Gensys Consultores Associados S/C Ltda.. The data set had 53,683, 45,136, 52,937 and 56,471 records on C, P, M and GND. The data were analyzed by restrict maximum likelihood method using animal models. The general model included the fixed effects of contemporary group, the age of cow at calving and the age of calf at weaning (linear and quadratic) and individual heterozygosis and the genetic direct effect, the maternal genetic effect and the permanent environmental effect as random. The direct heritabilities estimated using uni trait analyses were 0.17, 0.15, 0.15 and 0.18, respectively, for C, P, M and GND. The genetic correlations estimated to visual scores performing bi-trait analyses showed positive association with genetics correlations between 0.92 and 0.96. The genetic correlations estimated between GND and the visual scores showed values between 0.65 and 0.81. These results indicate that selection for visual scores and GND at weaning could be applied for these traits and also should result in indirect selection response for average daily weight, because these traits exibit similar estimates of heritabiliy and high correlations.

KEY-WORDS:

Genetic correlation. Pre-weaning growth. Frame. Heritability. Musculature. Maturation.