Records of LargeWhite breed animals were used to estimate variance components, genetic parametersand trends for the character total number of born piglets (TNBP) as measureof litter size. For obtaining variance components and genetic parameters, itwas used the Restricted Maximum Likelihood Method using MTDFREML software. Twomixed models (additive and repeatability) were evaluated. The additive modelcontained fixed effect of the contemporary group and the following random effects:direct additive genetic and residual effect for the first parturition. Repeatabilitymodel had the same effects of the additive model plus parturition order fixedeffect and non-correlated animal permanent environment random effect for thesecond, third and forth parturition. Direct additive heritability estimatesfor TNBP were 0.15 and 0.20 for the additive and repeatability models, respectively.The estimate of the ration among variance of the non-correlated effect of animalpermanent environment effect and the phenotypic variance, expressed as totalvariance proportion (c2) was 0.09. The estimates of yearly genetic trends obtainedin the additive and repeatability models have similar behaviors (0.02 piglets/sow/year).
