Uso de modelo de regressão aleatória na análise de produção de leite em bubalinos

Abstract

Data comprising 1,719 milk yield controls of 357 females predominantly Murrah breed, daughters of 110 sires, whose birth had occurred between the years of 1974 and 2004, obtained from the Programa de Melhoramento Genético de Bubalinos (PROMEBUL) with the addition of records proceeding from the herd of the EMBRAPA Amazônia Oriental - EAO, located in Belém, Pará, State, were used to compare random regression models, for estimating variance components and predicting breeding values of the sires... The data of milk yield were analyzed by different random regression models using the Legendre’s orthogonal polynomials functions of second, third and fourth order . The random regression models included the effects herd-year, month of parity date of the control, regression coefficients for age of females (in order to describe the fixed part of the lactation curve) and random regression coefficients related to the direct genetic effects and the permanent environment. The comparisons among the models were based in the Akaike Criteria Infromation. The random regression model which used the third order Legendre’s polynomials and four class of the environmental effect was the model which better described the additive genetic variation of the milk yield The heritability estimates obtained varied from 0.08 to 0.40.. The genetic correlations between milk yield in ages more near, were close to unit, but in ages less close, the correlations were low. The Pearson and Spearman’s correlations between the predicted breeding values of sires in all situations were close to the unit.