Effects of Long-Term Feeding of Milk and Milk Components to Rats

Abstract

To study effects of long-term feeding of milk and of certain milk components, but with butteroil reduced to supply 30% of calories, rats were fed a diet composed principally of dried milk, or purified diets with the same protein, fat, and carbohydrate content and with the fat (corn oil) or part of the carbohydrate (cornstarch), or both, replaced by milk fat and lactose. Food intakes, weight gains, and fat-free weights of rats fed the milk diet were lower than those of rats fed the purified diets. For rats fed purified diets, gross calorie intakes were similar, but weight gains were higher for rats receiving cornstarch than for rats fed lactose. Differences in digestible calorie intakes accounted for part but not all of the differences in gain. Calcium absorption was higher for rats fed milk and lactose-butteroil diets, but not for those fed the lactose-corn oil diet, than for those fed no lactose. Carcass Ca contents of lactose-fed groups were similar and higher than those of cornstarch-fed groups. Kidney stones were found in 47% of rats fed the milk diet, 29% of those fed lactose-butteroil, in 1 animal fed lactose-corn oil, and in no animals fed cornstarch.