IMPACT OF THE UNEVEN DISTRIBUTION OF THE NUMBER OF PROGENIES BY SIRES IN THE GENETIC EVALUATION OF ANIMALS IN ENVIRONMENTS WITH PRESENCE OF HETEROGENEITY OF ENVIRONMENTAL VARIANCE

Abstract

A progeny test representing the milk yield was simulated to evaluate the effect of heterogeneity of environmental variance on genetic evaluation of sires in situations of unequal number of progeny per sire between herds, eliminating, at random, daughters per sires in environments of low and high environmental variability. In all situations involving loss of information in the environment of lower environmental variability, there was larger overestimation of the residual variance component, resulting in lower estimates of heritability. On the other hand, the decrease in the amount of information of herds from high environmental variability led to greater overestimation of additive genetic variance and lower overestimation of environmental variance. Although there were alterations in breeding values regarding sires, Spearman and Pearson correlations between breeding values, in all situations, were higher than 0.90. The uneven number of progeny per sire in the presence of heterogeneity of environmental variance led to the overestimation of variance components and changes in absolute breeding values of the sires, without, however, changing the classification values. 
Keywords: genetic evaluation; genetic parameters; selection.