Trophic factors in mammalian colostrum promote the growth of the small intestine of neonates. To investigate the effect of colostrum feeding on the expression of specific intestinal proteins, animals were reared in a minimal disease unit and fed either sow colostrum or a commercial substitute by gastric intubation at 3-hour intervals over the first 24 h of life. Animals were then reared on a commercial milk replacer and fed over a maximum period of 5 weeks. Intestinal protein, DNA and histology data suggested a positive effect of colostrum on intestinal growth in the initial postnatal period. At week 1 post partum intestinal lactase was found to decline significantly in colostrum-fed (CF) piglets compared to substitute-fed animals. This effect was no longer apparent at 3 and 5 weeks post partum. Sucrase activity was significantly greater in CF piglets and this effect was sustained during the 5 postpartum weeks studied. The changes in enzyme activity could be correlated with posttranslational sialylation of intestinal membranes. These result suggest that feeding colostrum enhances the maturational decline in lactase activity and the expression of sucrase activity. The role of glycosylation of enzyme proteins in relation to their biological activity is discussed.