Procedures evaluation in the estimates of genetic parameters of cattle

[摘要] - Estimates of variance, covariance and heritabilities (h2) for body weights at birth (y1), weaning (y2), 12 (y3), 18 (y4) and 24 (y5) months of age, and scrotal circumference at 12 months of age (y6) were obtained from three data sets of purebreed Canchim males and females, born from 1961 to 1969 in São Carlos, São Paulo State. The genetic parameters were obtained by means of univariate analysis by Henderson Method 3, Maximum Likelihood (ML), Restricted ML (REML), Iterative Henderson Simple Method, Minimum Variance Quadratic Unbiased Estimation (MIVQUEo) and GLM procedure of SAS, and multivariate analysis by IHSM, ML and REML, with and without the relation matrix of animals. The heritability estimates ranged from 0.33 to 0.34 (y1), 0.30 to 0.81 (y2), 0.28 to 0.68 (y3) 0.27 to 0.27 (y4), 0.40 to 0.40 (y5) and 0.40 to 0.40 (y6). No normality of data for almost all traits and heterogeneity of variance for fixed effects of gender, year and season of birth, age of dam at calving, animal generation and random effect of sire was detected. Data transformation into normal scores provided the most efficient way to bring data near to a normal distribution. Estimation methods, type of analysis (univariate or multivariate analysis), sampling and type of transformation procedure, in this order, were the factors that influenced the most the heritability estimates.

[学科分类] 兽医学

[关键词] beef cattle;estimation methods;variance components     IntroduçãoPara planejar e orientar um programa de melhoramento genético de bovinos;é necessário estimar parâmetros genéticos;utilizando-se dados desbalanceados;sujeitos a grandes influências ambientais e de manejo