Effect of intermittent feeding on the development of disaccharidase activities in artificially reared rat pups.

We investigated the effect of an intermittent feeding schedule on the development of disaccharidase activities in the small intestine of artificially reared (AR) rat pups. Rat pups were fitted with an intragastric cannula at 5 days of age. A milk formula similar to the composition of rat milk was supplied by intermittent gastric infusion over the following 15-19 days. The body weight gain and plasma corticosterone levels of the AR pups matched those of pups reared naturally by dams (MR pups). At 10, 15 and 19 days of age, the small intestine from the ligament to Treitz to the ileocecal junction was divided into three segments of equal length and enzyme activities were measured in each. At the age of 10 and 15 days, sucrase and isomaltase activities were undetectable in AR pups fed according to a controlled schedule from the early postnatal period. These activities were first detected in the middle segment of the small intestine at 9 days of age in both AR and MR pups. Sucrase and isomaltase activities at the age of 19 days were diurnal in AR pups, but arrhythmic in MR pups. We conclude that artificial rearing via the intermittent gastric infusion of a milk formula containing only lactose as the carbohydrate source did not prematurely increase intestinal sucrase and isomaltase activities. Diurnal changes started from the beginning of development of these enzyme activities in AR pups.