Maternal dietary leucine supplementation affects apparent lactational activity and pup development in rats

Previous work from this laboratory has shown mildly elevated dietary leucine to alter the rhythm of prolactin secretion and to interfere with normal estrous cycling in the intact female rat. In this study, we have determined whether these observed effects on prolactin and cycling in turn affected fertility, gestation, mammary gland development or mammary gland morphology during lactation. Groups of control and leucine-supplemented mothers were mated with tested male breeders and a daily record was kept of pup births, pup deaths and general health and development of the pups. The day after weaning, mammary tissue was removed from dams in both groups and prepared for histological examination. In light of the previous results showing estrous cycle interruption and altered prolactin secretion, we report what was a surprising lack of effect of leucine supplementation of fertility, maintenance of gestation or overall development of the mammary glands in this species. Interestingly, however, dietary leucine supplementation was found to markedly after the histological appearance of lactating mammary tissue and to cause a significant increase in the number of litters that contained notably underdeveloped pups.