Genetic aspects of piglet survival

Amongst all fully formed piglets at the end of gestation, piglet survival until weaning (PS) is on average 81%. Selection for fast lean growth and increased litter size tends to decrease piglet survivability. Estimated heritabilities for PS and its component traits are generally low, on average around 0.04. Despite this, selection for improved survival is possible since the genetic variance for the trait is substantial. Genetic analyses indicated significant genetic correlations between PS on one side and litter size, gestation length, within-litter variation in birth weight, feed intake, gain, and backfat on the other. Genetic correlation of PS with birth weight, however, was low. Selection on birth weight as an indirect way to improve PS is doubtful. Genetic differences between piglets in survivability will be reflected in differences in body composition rather than in differences in birth weight. Experimental work on litters with high versus low genetic merit for PS, results of various selection experiments and experimental work with Meishan pigs support these findings.