CHANGES IN THE COMPOSITION OF PLASMA VERY-LOW-DENSITY LIPOPROTEIN DURING PREGNANCY AND LACTATION IN GENETIC LINES OF PIGS

Plasma very lour density lipoproteins (VLDL) of gilts were separated i nto two subfractions according to their affinity for heparin. Tile pro portion of VLDL present as subfraction 2 (higher affinity for heparin) varied, according to the genetic line of the pigs, between 0.21 and 0 .78 in virgin gilts. The proportions were related to the variation in piglet survival in the same nine genetic lines by a quadratic equation , which predicted that greater than 90% survival to weaning was to be found in piglets born to gilts having between about 0.3 and 0.7 of the ir VLDL as subfraction 2. This observation suggests a simple measureme nt that could be used in the selection of sows for a breeding programm e. The proportion of subfraction 2 fell throughout pregnancy in each o f three genetic lines measured and only returned to pre-pregnant value s after weaning: these changes did not correlate with the changes in t he lipid composition of plasma VLDL measured during pregnancy and lact ation. The findings suggest a role for the VLDL subfractions in contro lling the nutrition of the neonatal pig.