Growth and reproduction in the chronically nutrient-deprived rat

The effects on growth and reproduction of chronic, moderate multiple deficiencies of protein, riboflavin, pyridoxine and vitamin A were studied in the rat. The effects of combined deficits on feed intake and feed efficiency and on the young were then determined. All deficits, singly or in combination, interfered with the increase in feed efficiency in pregnancy seen in the control rats. Rats fed diets deficient in both protein and vitamin A did not survive to breeding weight. Protein deficiency resulted in reduced number of live young which were of reduced weight. When deficits of riboflavin or pyridoxine or both were also imposed, even fewer live young were produced, but there was no further effect on weights at birth. Reduction in feed intake in pair-fed animals was not totally responsible for these effects. Production of live young was not as depressed by combined vitamin deficiencies when dietary protein was adequate. The most severe effects of any of the deficiencies appeared to occur early in the reproductive process, possibly involving ovulation, embryo survival, implantation and the very early post-implantation period during the development of vital organs. It is suggested that the nutrient deficit interferes with the action of progesterone or other hormones important to the physiological adaptations to pregnancy.