Effects of feeding on the small intestinal mucosa of beagle pups during the first 5 d of life.

To further define the effects of feeding on small intestinal ontogeny, naturally suckled and formula-fed beagle pups were studied over the first 120 h of life. In suckled animals, proximal jejunal and midintestinal mucosal weight and protein and DNA contents increased > 75% by 24 h (P < 0.005), with no further increases at 120 h. In formula-fed pups, no mucosal mass changes were found between 0 and 72 h of life. At 120 h, proximal jejunal mucosal weight and protein and DNA contents were significantly greater than in newborns (P < 0.005) and were similar to values for suckled animals at the same time. No significant mid-intestinal or terminal ileal growth was noted in formula-fed pups at any time. Specific and total activities of proximal jejunal brush border lactase, sucrase, and alkaline phosphatase were significantly greater in suckled vs formula-fed animals at 120 h. In a parallel study to assess postnatal effects of mature milk vs colostrum, significant mucosal growth at 24 h of life was demonstrated in pups suckled by surrogate dams who had whelped 21 d previously. These data indicate that both natural suckling (colostrum or milk) and formula feeding support enteric mucosal growth in newborn dogs; however, the two feeding regimens are characterized by unique ontogenic patterns of intestinal mucosal growth and function.