VALIDATION IN WELL-NOURISHED AND POORLY-NOURISHED RATS OF A METHOD TOCOLLECT MILK FOR COMPOSITIONAL ANALYSIS

The nursing method of milk collection is a procedure in which milk is collected from the stomachs of rat pups after they are allowed to suck le. When dams are undernourished, higher volumes can be obtained this way than by expressing milk from the dam's nipple. However, compositio n of the milk is changed by being in the pups' stomachs. To validate t he nursing method of milk collection for use among pups differing in n utritional status, we determined whether this change in composition is the same in well-and poorly nourished pups. Milk was collected from w ell-nourished dams, pooled, and its macronutrient composition determin ed. This milk was fed by gavage to 14-d-old pups of rat darns given fr ee access to diet AIN-93G(TM) (control) or restricted to 50% of the av erage intake of control rats (food-restricted). Their stomach contents were collected 30 min later. There were no significant differences be tween the pups of control and food-restricted dams in the composition of the milk curd recovered from the pups' stomachs. As expected, the p ups' stomach contents had significantly lower water, fat and lactose c oncentrations than the pooled milk fed. Thus, the nursing method of mi lk collection does not provide a sample suitable for the determination of the absolute composition of the milk fed. Inasmuch as pup undernut rition does not differentially affect the compositional changes that o ccur when milk is in the pups' stomachs, the nursing method of milk co llection provides a valid comparison of the relative composition of th e milk consumed for pups who differ in nutritional status. (C) 1998 El sevier Science Inc.