Variance components of fertility in Spanish Landrace pigs

Fertility is a discrete trait with two categories (1, successful mating, 0, unsuccessful mating). A Bayesian analysis with a binary threshold animal model has been performed with 18 695 Al mating records from 1987 to 1997, concerning 4085 sows and 187 boars. The pedigree included all individuals genetically linked with data. The binary response was modeled under a probit approach. The model for liability includes paternal and maternal genetic and permanent environmental effects, 54 herd-year-season and seven order of parity effects. Posterior mean (and standard deviation) for paternal heritability was 0.028 (0.014), for maternal heritability 0.038 (0.014), and 0.028 (0.009) and 0.072 (0.017) for ratios of paternal and maternal permanent environmental effects. Posterior mean (and standard deviation) of genetic correlation between paternal and maternal genetic effects was -0.513 (0.264). Differences between parities suggest that fertility is bigger in second parity than in the first one, and decrease in subsequent parities. (C) 2001 Elsevier Science B.V. All rights reserved.