Technical Abstract: In postnatal life, the growth rate of the pig is most rapid during the neonatal and weaning periods. Nutrition and gastrointestinal function play a critical role in the survival, health and growth of the young pig during this transition from suckling to weaning. The high metabolic rate and cellular turnover of gut tissues result in substantial first-pass utilization of dietary nutrients, especially amino acids, to maintain gut function. The changes in the diet composition and gut microflora after weaning are associated with increased gut growth and metabolism, which may limit the systemic availability of dietary nutrients. Strategies aimed at limiting gut metabolism and supplementing key gut-nutrients in support of gut function may improve growth.