Bi-phasic allometric growth of the small intestine, cecum and the proximal, middle, and distal colon of rats (Rattus norvegicus Berkenhout, 1764) before and after weaning.

We studied whether the growth of the intestinal tract changes at weaning. We weighted fresh tissue and measured segment length of the small intestine, cecum and proximal, middle, and distal colon of 45 male and 51 female F344/Yit rats (Rattus norvegicus Berkenhout, 1764) of 0 to 428 days old. We performed correlation analysis among tissue weight, segment length and empty body weight after logarithmic transformation of the data. The growth of the small and large intestine was biphasic. Intestinal growth exceeded body growth during the suckling period and slowed down suddenly after weaning. Sexual differences existed in intestinal growth, although much smaller than the difference before and after weaning. These results appear to suggest that the size of intestinal tract of the rat does not adapt to nutritional changes at weaning, but prepare for weaning beforehand.