Study of the Effect of Autoselection on Heritability and Selection Response in Reproductive Traits

Autoselection is a kind of natural selection, that occurs in reproductive traits by inequality of offspring generation and therefore by virtue of the nature of its genes transmission to next generations. In this study, the effects of autoselection on heritability and selection response in reproductive traits by using univariate stochastic computer simulation in artificial selected and unselected populations were investigated. The results showed that, in autoselection and no artificial selection on litter size, additive genetic mean, phenotypic mean and threshold mean increased. Additive genetic variance and heritability had no changes. In autoselection and artificial selection for threshold phenotype on dams and in autoselection and artificial selection for threshold phenotype on dams and for sires base on their mother’s threshold phenotype, the results showed that in high heritability, observed selection response for per generations was more than last generation because with increasing threshold mean, the distribution of threshold phenotype in dam’s population and autoselection response depends to this distribution. Although, autoselection and artificial selection occurred additive genetic variance and heritability had decreased a little, because artificial selection base on threshold phenotype and autoselection prevent to decrease additive genetic variance. Analysis of threshold phenotypic data by MATVEC with threshold model, showed that estimated heritability was less than real underlying heritability and its estimation depends on real underlying heritability, proportion selected and paths of selection.