Effects of varying degrees of chronic dietary restriction in rat dams on reproductive and lactational performance and body composition in dams and their pups.

To assess the effects of varying degrees of chronic dietary restriction, rats were fed ad libitum or were restricted to 75%, 50% or 40% of ad libitum intake beginning 28 days prior to breeding and continuing through day 14 of lactation. Pup birth weight did not differ among the groups, but maternal weight gain, net maternal growth, and litter number were proportional to dietary intake. During lactation, maternal weight loss was minimal in all groups and carcass protein proportions remained constant. However, maternal fat stores were mobilized in all groups, with smaller changes in the 50% group. Milk yield was reduced in restricted dams. Despite a partial compensation in milk yield by the 75% group, litter weights were proportional to maternal dietary level. In contrast, rats in the 50% group made no compensation in milk yield. Possible explanations for the discrepancy between milk yield and litter growth are explored.