Piglet preweaning survival and its relationship with the breeding goal of a large White boar line

Aim of this study was to investigate piglet preweaning survival and its relationship with a total merit index (TMI) used for selection of breeding candidates in the C21 Large White boar line. Data on 13,924 crossbred piglets (1,347 litters), originated by 189 Large White boars and 328 Large White-derived crossbred sow, were analyzed under a frailty proportional hazards model, assuming a piecewise Weibull distribution and including sire and litter as random effects. Estimated hazard ratios (HR) indicated that sex, cross-fostering, year-month of birth, parity of the nurse sow, size of the litter and class of TMI were significant effects for piglet survival. Female piglets (HR = 0.80) had less risk of dying than males as well as cross-fostered piglets (HR = 0.50). Survival increased when parity of the nurse sow increased up to the fourth parity (HR = 0.70), but further increases of parity did not enhance pre-weaning survival. Piglets of small (HR = 3.13) or very large (HR = 3.69) litters had less chances of surviving in comparison with litters of intermediate size. Class of TPI exhibited an unfavourable relationship with survival (HR = 1.23 for the TMI top class). Estimated heritability of survival was 0.025. These results suggest that piglet preweaning survival should be included in the breeding goal of the C21 boar line.