Genetic correlations between litter size and weights, piglet weight variability and piglet survival from birth to weaning

Genetic parameters of litter size, litter weight, mean and heterogeneity (within-litter standard deviation) of individual piglet weights at birth, 21 days of age and at weaning, of perinatal (PSR) and birth to weaning (BWSR) survival rates were estimated in a Large White population using restricted maximum likelihood methodology applied to a multiple trait animal model. A total of 1958 litters produced by 1131 sows was analysed. Litter size at weaning and survival rates had a high phenotypic variability, but very low heritability values (0.02±0.01 to 0.03±0.01). The heritability estimates were larger for the other traits, but remained rather low for litter size and litter weights (0.11±0.02 to 0.13±0.03) as well as standard deviation of piglet weights (0.06±0.01 to 0.10±0.02), and were moderate for mean piglet weights (0.20±0.02 to 0.32±0.03). A genetic antagonism was obtained between BWSR on one hand, PSR, litter size and weight at birth on the other hand (-0.22±0.32 to -0.57±0.51). Similarly, piglet weight heterogeneity was genetically associated with lower piglet survival rates at farrowing (-0.21±0.19 to -0.35±0.25) and, above all, from birth to weaning (-0.44±0.23 to -0.99±0.06). Mean piglet weights had moderate favourable genetic correlations with BWSR (0.13±0.19 to 0.34±0.23), but unfavourable genetic relationships with PSR (-0.01±0.27 to -0.49±0.24).