Genetic Parameters of reproductive traits recorded at different parities in Landrace and Large White sows

The use of relevant and reliable genetic parameters such as heritabilities and genetic correlations should be considered as a priority in any breeding program in order to "fine tune" the genetic evaluation procedures. It was suggested by Walters (1998) that nucleus breeders' should use in their breeding programs the specific parameters from the herd(s) of origin and recalculate those estimates periodically. Therefore, knowledge of genetic parameters of reproductive traits is essential to estimate accurate breeding values by accounting for all correlations available in a multivariate BLUP analysis. In addition, Roehe and Kennedy (1995) suggested that genetic parameters will allow the breeder to combine different traits in selection, to optimise breeding schemes, and to predict genetic response to selection. Estimates of genetic parameters can be biased by involuntary and directional selection from parity to parity (Roehe and Kennedy, 1995). In order to avoid this possible biasness, parities 1, 2 and 3 were analysed as separate traits using residual maximum likelihood methods under a tri-variate animal model. The objective of this study was to estimate heritabilities and genetic correlations for reproductive traits.