The present study was undertaken to study the effect of inbreeding on pre-weaning and sow performance traits of Large White Yorkshire pig population. Data on 7596 Large White Yorkshire pigs maintained at PGRIAS, Kattupakkam from the period of 1990 to 2015, were subjected to least square analysis to study the effect of inbreeding and other non-genetic factors viz., period, season, sex, parity, litter size at birth on various traits using general linear model. Inbreeding was calculated as Wright’s path co-efficient. The mean inbreeding co-efficient of LWY population studied was 2.45 %. Among 7596 animals in the pedigree, 2088 were inbred and the range of individual inbreeding co-efficient (F) was from 0 to 37.5 per cent. The average inbreeding in the inbred population was 8.92 %. The effect of inbreeding was found to be significant for weaning weight, pre-weaning average daily gain and litter weight at weaning, where the traits were found to increase with inbreeding (enhancement). The absence of depressive effect on fitness traits observed in the present study could be due to lower levels of inbreeding, which was possible due to periodic introduction of breeding animals and planned mating.

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Background: 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. Methodology: 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. Conclusion: 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.

A study was conducted to evaluate the individual and sow performance traits of Large White Yorkshire × desi crossbred pigs at All India Co-ordinated Research Project on Pigs (AICRP), Kattupakkam. The genetic groups studied were 50% LWY (100% LWY × 100% desi), 50% LWY inter se (50% LWY 50% desi × 50% LWY 50% desi), 75% LWY (100% LWY × 50% LWY 50% desi) and 75% LWY inter se (75% LWY 25% desi × 75% LWY 25% desi). The (co)variance components for different traits were estimated by restricted maximum likelihood method (REML). The average inbreeding in the whole population was 5.4%. Maternal genetic and common litter effects were important random sources of variation in individual traits. The least-squares mean for birth weight (BW), weaning weight (WW), average daily gain up to weaning (ADG), market weight (MW), pre-weaning mortality (PWM), age at first farrowing (AFF), litter size at birth (LSAB), litter weight at birth (LWAB), litter size at weaning (LSAW), litter weight at weaning (LWAW) and farrowing interval (FI) were 1.079 kg, 7.906 kg, 142.238 g, 8.4%, 62.208 kg, 456.829 days, 197.994 days, 6.792, 8.174 kg, 6.347 and 60.649 kg, respectively, and the direct heritability obtained through the best model were 0.069, 0.015, 0.012, 0.031, 0.291, 0.019, 0.173, 0.257, 0.076 and 0.157, respectively. The repeatability estimates for LWAB, LSAW, LWAW and FI were 0.265, 0.258, 0.263 and 0.762, respectively. The 75% LWY were better in terms of production and reproduction traits and the high heritability for litter traits provided good scope for improvement.