Relevance of purebred information for predicting genetic merit of survival at farrowing of crossbred piglets

The objective was to infer (co) variance components for survival at farrowing in purebred (P) and crossbred (C) pigs. Data were from 13,643 (1,213 litters) C and 30,919 (3,162 litters) P pigs, produced by mating the same 168 P boars to 319 Large White-derived crossbred females and 1,413 P sows, respectively. The outcome variable was pig survival at birth, coded as a binary trait. A Bayesian bivariate threshold model was implemented via Gibbs sampling. Effects of sex, parity of the dam, litter size and year-month of birth were assigned flat priors; those of litters, dams and sires were given Gaussian prior distributions. Marginal posterior means (SD) of the sire and dam variances in P were 0.018 (0.008), 0.077 (0.020), respectively in the liability scale. For C, corresponding estimates were 0.030 (0.018) and 0.120 (0.034) respectively. The posterior means (SD) of heritability of survival in P and C, and of the genetic correlation between these traits were 0.049 (0.023), 0.091 (0.054) and 0.248 (0.336), respectively. The genetic correlation was also low, and a 95% Bayesian confidence region (-0.406, 0.821) included zero. Even tough uncertainty of estimates is large, results suggest that genetic progress for survival at birth expected in C when selection is based on P may be nil.