Reproduction and lactation in the rat on highly purified diets.

During recent years much work has been carried out to determine what vitamins and other nutritional factors are necessary for successful reproduction and lactation in rats and mice. Earlier work in this field has been reviewed by Folley, Ikin, Kon & Watson (1938) and by Foster, Jones, Dorfman & Kobler (1943). Nakahara and his co-workers (Nakahara & Inukai, 1933; Nakahara, Inukai & Kato, 1934; Nakahara, Inukai, Kato & Ugami, 1936) have described a diet on which rats would reproduce, but on which successful lactation could only be obtained by the addition of factors L, and L, which were present in liver and yeast respectively. Folley et al. (1938), using an apparently similar diet, failed to confirm these findings; they found that this basal diet was comparable with their stock diet as regards reproduction and lactation, and that consequently the addition of yeast or liver to the experimental diet had little or no effect. Later Nakahara, Inukai & Ugami (1939) pointed out that they had used a special type of baker’s yeast deficient in factors L, and L, and suggested that the brewer’s ygast used by Folley et al. (1938) had presumably contained both these factors. Experiments have been in progress here for over five years in which reproduction and lactation have been studied with rats receiving a basal diet of purified foodstuffs and supplemented with the known vitamins alone or with various other additions. A preliminary report of some of these experiments has been published elsewhere (Folley, Henry & Kon, 1942). A full account of the findings is given in the present communication.