NUTRIENT-INDEPENDENT AND NUTRIENT-DEPENDENT FACTORS STIMULATE PROTEIN-SYNTHESIS IN COLOSTRUM-FED NEWBORN PIGS

We hypothesized that nonnutrient components, including growth factors, present in colostrum contribute to the stimulation of protein synthes is in colostrum-fed neonatal pigs. We studied neonatal pigs fed mature milk, colostrum, or a formula containing a macronutrient composition comparable to that of colostrum for 24 h. We measured the circulating concentrations of insulin, insulin-like growth factor I, glucose, and amino acids at intervals throughout the 24-h period, after which we me asured in vivo protein synthesis using a flooding dose of [H-3]phenyla lanine. The rates of protein synthesis in several tissues measured aft er 24 h of feeding were greater than those we reported previously afte r 6 h of feeding. The acute (within 6 h) stimulation of protein synthe sis in visceral and skeletal muscle tissues of neonatal pigs fed milk, colostrum, or formula was primarily influenced by nutrient intake and associated with rapid secretion of insulin. Indirect evidence suggest s that intestinal absorption of ingested colostral insulin was minimal . However, the sustained increase in tissue protein synthesis between 6 and 24 h coincided with an increase in circulating insulin-like grow th factor I. We found a novel, specific stimulation of skeletal muscle and jejunal protein synthesis in colostrum-fed pigs that can be attri buted to some nonnutrient component of colostrum.