BACKGROUND: Preterm infants often tolerate full enteral nutrition few weeks after birth but it is not known how this is related to gut maturation. Using pigs as models, we hypothesized that intestinal structure and digestive function are similar in preterm and term individuals at 3-4 weeks after birth and that early enteral nutrition promotes maturation.

METHODS: Preterm or term cesarean-delivered pigs were fed total parenteral nutrition (TPN), or partial enteral nutrition (ENT, 16-64 mL/kg/d of bovine colostrum) for 5 d, followed by full enteral milk feeding until d 26. The intestine was collected for histological and biochemical analyses at d 0, 5 and 26 (n = 8-12 in each of ten treatment groups).

RESULTS: Intestinal weight (relative to body weight) was reduced in preterm pigs at 0-5 d but ENT feeding stimulated the mucosal volume and peptidase activities. Relative to term pigs, mucosal volume remained reduced in preterm pigs until 26 d although plasma glucagon-like peptide 2 (GLP-2) and glucose-dependent insulin-trophic peptide (GIP) levels were increased. Preterm pigs also showed reduced hexose absorptive capacity and brush-border enzyme (sucrase, maltase) activities at 26 d, relative to term pigs.

CONCLUSION: Intestinal structure shows a remarkable growth adaptation in the first week after preterm birth, especially with enteral nutrition, while some digestive functions remain immature until at least 3-4 weeks. It is important to identify feeding regimens that stimulate intestinal maturation in the postnatal period of preterm infants because some intestinal functions may show long-term developmental delay.