Revista Brasileira de Zootecnia
On-line version ISSN 1806-9290
BARBOSA, Leandro et al. Estimation of variance components, genetic parameters and genetic trends for litter size of swines. R. Bras. Zootec. [online]. 2010, vol.39, n.10, pp. 2155-2159. ISSN 1806-9290. http://dx.doi.org/10.1590/S1516-35982010001000008.
Records of Large White breed animals were used to estimate variance components, genetic parameters and trends for the character total number of born piglets (TNBP) as measure of litter size. For obtaining variance components and genetic parameters, it was used the Restricted Maximum Likelihood Method using MTDFREML software. Two mixed models (additive and repeatability) were evaluated. The additive model contained fixed effect of the contemporary group and the following random effects: direct additive genetic and residual effect for the first parturition. Repeatability model had the same effects of the additive model plus parturition order fixed effect and non-correlated animal permanent environment random effect for the second, third and forth parturition. Direct additive heritability estimates for 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 animal permanent environment effect and the phenotypic variance, expressed as total variance proportion (c2) was 0.09. The estimates of yearly genetic trends obtained in the additive and repeatability models have similar behaviors (0.02 piglets/sow/year).
Keywords : genetic trend; heritability; number of piglets; REML; repeatability model; reproductive traits.