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 m odel has been performed with 18 695 Al mating records from 1987 to 1997, co ncerning 4085 sows and 187 boars. The pedigree included all individuals gen etically linked with data. The binary response was modeled under a probit a pproach. The model for liability includes paternal and maternal genetic and permanent environmental effects, 54 herd-year-season and seven order of pa rity effects. Posterior mean (and standard deviation) for paternal heritabi lity 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 env ironmental effects. Posterior mean (and standard deviation) of genetic corr elation between paternal and maternal genetic effects was -0.513 (0.264). D ifferences between parities suggest that fertility is bigger in second pari ty than in the first one, and decrease in subsequent parities. (C) 2001 Els evier Science B.V. All rights reserved.