Estudos genéticos sobre a leitegada em suínos da raça Landrace criados no Rio Grande do Sul

Abstract

The goals of this research were to obtain genetic parameters and estimate genetic trends in Landrace pigs. Data consisted of records from 927 granddams, 2,537 dams and 8,887 litters raised in the state of Rio Grande do Sul, Brazil, provided by the Swine Breeders Brazilian Association - ABCS. Variance components were estimated by REML, using a model that included the direct genetic effect, maternal effect, common litter effect and the fixed effect of contemporary group. Contemporary groups were defined as a combination of farm, year, and season of farrowing. The model also included the covariates parity order, age of sow at first litter and age of sow at last litter. Direct genetic and maternal genetic trends were estimated by regression of direct genetic values on birth year of the dam. Heritability and maternal heritabilities were, respectively, .002 and .012 for litter size at birth (NLN), .003 and .009 for litter size at 21 days (NLD), .024 and .013 for average litter weight at birth (PMNasc), .000 and .008 for average litter weight at weaning, in kg, adjusted to 21 days (PMD), .000 and .007 for average daily weight gain (GMD), .028 and .010 for number of stillborn (NatMort). Analysis of variance for genetic trend showed significance for direct and maternal genetic effects for NLN, NLD, PMNasc and NatMort but not for PMD or GMD. Genetic trends were positive for NLN (0.0007/ 0.0018 g/year), NLD (0.001/ 0.0017 g/year), GMD (5E-06/ 0.0003 g/year) and negative for (-0.0001/ -8E-05 g/year), PMD (-1E-05/ -7E-05 g/year) e NatMort (-0.002/ -1E-05 g/year). © 2008 Sociedade Brasileira de Zootecnia.