Dietary Restriction and Reproduction in the Rat

Abstract

The effects of varying levels of food intake on reproduction were observed in Sprague-Dawley rats. The diet consisted of commercial pellets composed of natural foods. Restriction was at 3 levels: 25, 50 and 75%. Maternal and fetal weights varied inversely with degree of restriction. Weight loss of restricted dams bearing young was no greater than that of rats failing to litter. Fetation was an all-or-none phenomenon in that full-sized litters developed or all implants resorbed. Resorptions occurred between days 8 to 11. Number of resorptions and number of viable embryos were nearly identical in 75%-restricted rats examined on day 13. Size of litters of 75%-restricted dams was practically the same on days 13 and 21, and equaled that of unrestricted dams examined at corresponding stages of gestation. Transitory unrestricted feeding during the first 2 or 3 days of pregnancy greatly reduced the incidence of resorptions in 75%-restricted rats, and feeding started on day 8 completely prevented them. Delay of transitory feeding to day 10 was less effective, and on day 12 had no effect. Fetal malformations were never observed. The results obtained with a restricted stock diet were similar to the reported observations in rats receiving a proteindeficient diet.