Differences in late prenatal development as an explanation for genetic differences in piglet survival

Explanations for increasing farrowing survival and postnatal survival with increasing genetic merit for piglet survival are likely to be found in a higher degree of foetal development or maturity during late gestation. This is substantiated by increased relative organ weights (adrenals, stomach, and small intestine), increased serum cortisol levels, increased glycogen reserves in liver and muscle, and an increased carcass fat percentage in litters with high genetic merit for piglet survival. The strong positive relationship between foetal cortisol and genetic merit for piglet survival possibly causes the majority of the observed differences in foetal development and maturity. Knowing that cortisol plays a major role in the preparation for the transition from intrauterine to extrauterine life, piglets with a higher genetic merit for piglet survival may have an improved ability to cope with hazards during birth and within the first days of life.