Artificial formula induces precocious maturation of the small intestine ofartificially reared suckling rats

Background: The artificially reared rat model was used successfully to stud y the effect of nutrition during the early postnatal period on growth and d evelopment of the neonate. Overgrowth and morphologic changes of the gastro intestinal tract are known consequences of artificial rearing. The major go al of our study was to elucidate whether artificial rearing-enhanced gut de velopment is caused by artificial diet or by gastrostomy and the artificial rearing technique itself. Methods: Suckling rats at day 8 of age underwent intragastric cannulation a nd were machine fed either a cow's milk-based artificial rat's milk substit ute or pooled rat's milk for 4 days. Dam-fed littermates served as a contro l. Results: Body growth did not differ in the three experimental groups. In ra ts receiving rat's milk substitute, small intestinal wet weight was approxi mately 60% greater than in rats fed rat's milk or control rats. Additionall y, the entire small intestine was approximately 20% longer in the mt's milk substitute group. Morphologically, mt's milk substitute-fed pups demonstra ted significantly greater intestinal villus length and crypt depth compared with rat's milk-fed or control rats. Jejunum and mid-jejunum of the rat's milk and control groups did not differ in these parameters. Intestinal sucr ase activity of rat's milk substitute-fed rats was significantly elevated c ompared with rat's milk-fed rats or control animals. Conclusions: These results indicate that cow's milk-based formula, not gast rostomy or artificial feeding technique, is a principal cause of the small intestine overgrowth and precocious maturation of some intestinal functions observed in artificially reared sucklings.