Postnatal ontogeny of small intestinal histomorphology, crypt cell proliferation and peptide transporter 1 gene expression in piglets

Ontogeny of the morphology, cell proliferation, and peptide transporters in each region of the small intestine support optimal nutritional status and growth of pigs from early to later life. To assess these, growth of piglets was studied at birth (d 0), suckling (d 7), weaning (d 21) and post-weaning (d 28, 49 and 77) days. Hematology, small intestinal histomorphology, crypt cell proliferation, and peptide transporter 1 (PepT1) mRNA expression were measured from the animals at newborn, and at 7, 21, 49 and 77 days old. Among the three age groups (newborn to 21, 21 to 28 and 21 to 77 days old), all animals progressively improved body weight (BW) and body weight gain (BWG) from the early suckling stage to the post-weaning stage (p<0.0001) but their BWG declined during one week after weaning (d 21 to d 28). In the youngest age group (d 0 to d 7), the villus height, ratio of villus height to crypt depth, proliferation, and turnover rate of enterocytes at distinct regions along the small intestine, particularly the jejunum, reached maximal value and then dramatically decreased by the day the animals were weaned (d 21) and thereafter (p<0.05). The PepT1 mRNA expression was found to be distributed along the small intestine. The relative expression of PepT1 mRNA in the suckling pigs paralleled that in the post-weaning pigs. These data suggest that ontogenetic adaptation of the histomorphology, crypt cell number, and turnover rate as well as relative expression of Pep T1 mRNA in the small intestine may be useful during early suckling state, especially the first week, and efficiently promotes diet transition post-weaning.