Estimação dos parâmetros e tendências genéticas de ovinos no Rio Grande do Sul

Abstract

The objective of the study was to verify the genetic parameters and trends, for the birth weight characteristic of sheep from two herds, of the Texel breed and of a maternal base system Polwarth and paternal sheep Finnish Landrace X Frisona Milchschaf. Therefore, verifying the animal model that best predicts the genetic values. Were used data sets of 783 and 1033 birth weight records, respectively, for the Texel breed herds and the crossing system. The analyzes were performed using the maximum likelihood restricted method under an animal model, considering the birth weight characteristic, using the WOMBAT program. For the herd of the Texel breed the model that best explained the partition of the variances was what considered the direct effects and permanent maternal environment. Thus, the direct heritability coefficient for birth weight was 0.011 ± 0.040 and the phenotypic variation attributed to the maternal permanent environment for the same characteristic was 0.394 ± 0.045. The direct genetic gains for birth weight were 0.103% per year, between the years of 2012 to 2016. The phenotypic progress for the same trait, at the same time, was 0.039 kg per year. In the herd with Polwarth sheep crossing with Sheep Finnish Landrace X Frisona Milchschaf the model that best fitted the data was what considered the direct effects, maternal and covariance between both. The direct, maternal coefficients of heritability and the correlation between direct and maternal effects for birth weight were, respectively, 0.20 ± 0.135, 0.54 ± 0.137 and -0.69 ± 0.254. The direct and maternal genetic gains for birth weight were 0.027 and -0.034 kg, respectively, from the years 2012 to 2016. The phenotypic variation, for the characteristic in question, in the same period, was 0.032 kg. In this sense, for the animals of the breed Texel the estimate of the coefficient of direct heritability is low, but with a high phenotypic variation attributed to the maternal permanent environment. In the system with Polwarth sheep crossing with Finnish Landrace X Frisona Milchschaf sheep, the direct and maternal genetic gains, between 2012 and 2016, for birth weight, are low but present good coefficients of determination of 0.42 and 0.30, respectively.