Comparison of the gastrointestinal growth-promoting effects of rat colostrum and mature milk in newborn rats in vivo

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Abstract
The purpose of this study was to compare the effects of rat colostrum and mature milk on newborn rat gastrointestinal growth under conditions that controlled the possible confounding effects of energy intake and mode of feeding. Newborn Sprague-Dawley rat pups were tube-fed equicaloric amounts of rat colostrum or mature rat milk for 40 h before they were killed. Compared to littermates that were killed immediately after birth, both groups of fed rats demonstrated increases in the weights of stomach and intestine, but there was no organ weight difference detected between colostrum-fed and mature milk-fed rat pups. However, both the concentration of DNA and the rate of synthesis of DNA in the intestines were greater in rats fed colostrum than in those at birth or those fed mature milk. Although the pancreas exhibited no detectable increase in weight by 41 h, the DNA concentration and total DNA content increased and RNA/DNA ratio decreased in both fed groups, also without apparent difference between rats fed colostrum and those fed mature milk. The rate of 3H-thymidine incorporation into DNA in pancreas, however, was greater in colostrum-fed pups than in mature milk-fed pups. These differences at 40 h age in intestinal and pancreatic cell replication activity, but not organ weights, can be ascribed to feeding colostrum.