Genetic evaluation of pre-weaning mortality in large white yorkshire pigs using threshold and linear models in hot and humid conditions of south India

Large White Yorkshire (LWY) breed has been extensively used for crossbreeding in India. Genetic evaluation of pre-weaning mortality (PWM) in LWY pigs maintained at Kancheepuram district of Tamil Nadu was done to understand adaptability of the breed to tropical conditions.

Pre-weaning mortality was recorded as a binomial trait, for which threshold models have been found to be appropriate. (Co)Variance components for random sources of variation including direct genetic, maternal genetic, maternal permanent environmental and common litter were estimated using linear and threshold models.Factors including inbreeding of the individual animal affecting the trait were included as fixed effects in the mixed models used.

The pre-weaning mortality of LWY pigs was comparatively lower indicating better adaptability of the breed. Inbreeding levels above 6 per cent were found to increase PWM. Common litter had significant influence on the genetic parameter estimates. Estimates obtained using threshold model were higher than those obtained by linear models. Threshold models provided solutions for complex models, which had convergence problems with the linear, REML method of estimation. Heritability estimates for PWM obtained through this study could be useful in formulation of breeding plan for LWY pigs in the country.