To determine if milk-borne insulin-like growth factor I (IGFI) is absorbed in neonatal piglets, recombinant human IGF-I was iodinated and then administered via an oral-gastric tube to newborn and 3-day-old piglets together with fluorescent isothiocyanate dextran (FITC-D70s, a macromolecular marker for assessment of gut closure). Results showed that total radioactivity and trichloroacetic acid (TCA)-precipitable radioactivity rose significantly in the plasma of both newborn and 3-day-old piglets 1 hour after oral-gastric administration of 125I-IGF-I, although the magnitude of increase was greater in newborns than in 3-day-old piglets. In contrast, significant absorption of FITC-D70s was observed only in newborn piglets but not in 3-day-old piglets. Chromatographic analysis revealed that 125I-IGF-I represented up to 20% of total plasma radioactivity in the newborns and up to 10% in the 3-day-old piglets. The 125I-IGF-I found in the plasma was mostly bound to IGF-binding proteins. These results indicate that milkborne IGF-I can be absorbed in neonatal piglets and the absorption is independent of gut closure.

The pancreas consists of two histologically distinct and functionally independent components, i.e., endocrine islets and exocrine acini. Cells in the endocrine islets produce hormones and regulate body metabolism via the blood circulation, while cells in the exocrine acini secrete digestive enzymes through the duct system into the duodenal lumen. The structure of the pancreas and its postnatal developmental changes in humans and laboratory rodents have been intensively reviewed in more recent publications (1-3). A similar review is lacking for the domestic animal species. This chapter focuses on morphological structure of the pancreas in pigs and its growth and structural changes during the postnatal period. Wherever possible, information derived directly from studies of pigs is used, or otherwise species origin of the data is defined. Comparisons with other domestic animal species are made when information is available.

This study examined the effects of milk protein pre-hydrolyzation on the crypt cell proliferation and morphological alterations in the small intestine in neonatal piglets. The newborn unsuckled Erhualian piglets were bottle-fed for 3 days with cow milk formula or pre-hydrolyzed cow milk formula. When compared with newborn pigs, the height of the intestinal villi decreased by 30-45% in jejunal region inmilk-fed piglets, while no significant change was observed in the intestinal villus height in piglets fed pre-hydrolyzed milk. Microscopic examination showed an atrophy of the intestinal villi and accelerated proliferation of crypt cells in the milk-fed piglets, possibly due to a hypersensitive reaction of the intestine to dietary protein. The results indicate that the nature of dietary protein had a significant effect on the intestinal structure. This finding may have a significant implication in infant care and animal feeding.

To investigate what factors lead to the rapid postnatal tissue growth and functional maturation in the newborn intestine we compared intestinal tissue mass and digestive enzyme activities between newborn unsuckled piglets and piglets bottle-fed for 3 days with either intact porcine colostrum or trypsinized porcine colostrum. Bottle-feeding of colostrum or trypsinized colostrum led to a significant increase in weight and length of the small intestine and a significant increase in mucosal weight of the large intestine. The mucosal protein content in the small and the large intestine and the mucosal DNA content in the large intestine increased significantly following 3-days bottle-feeding of porcine colostrum or trypsinized colostrum. The total mucosal DNA contents in the small intestine of piglets fed colostrums or trypsinized colostrum were, respectively, 39 and 64% greater than that in the newborn unsuckled piglets. The numbers of cells labeled with BrdU in intestinal crypts also increased significantly in piglets fed both diets compared with that of newborns. But a marked increment in villus height was observed only in piglets fed intact colostrum. Brush-border membrane enzymes showed a differential response to the dietary treatment. Bottle-feeding of intact porcine colostrum, but not trypsinized porcine colostrum led to a significant increase in lactase, alkaline phosphatase and aminopeptidase specific activities in the small intestine. In contrast, the specific activity of maltase in the small intestine increased significantly with age irrespective of dietary treatment. These results indicated that genetic and dietary factors are involved in regulating postnatal intestinal development, and porcine colostrum contains a trypsin-labile component which can increase lactase and alkaline phosphatase activities in the newborn intestine.