Reproduction failures of rats and mice on synthetic or whole-plant rations have been described and attributed to a lack of animal protein factor (APF) or vitamin B12 (1-4). We have succeeded in breeding mice, kept on whole-plant rations, for several generations; nearly normal reproduction and mortality rates were observed although the animals showed symptoms of vitamin B12 deficiency.
The experimental diets contained 22-4% of crude protein (N X 6.25). Diet III had the following composition: expelled sesame-oil cake-meal, 46.5%; ground yellow corn, 46.5%; cottonseed oil containing 0.2% of percomorphum and 0.2% of wheat germ oil, 5%; U.S.P. salt containing 0.1% of CoCl2, 2%; 10 B-complex vitamins as described (4). Albino mice were kept on a commercial stock ration, containing 24% of crude protein (13.5% of animal origin) prior to the start of the experiments. Pregnant females were put in individual screen-bottomed cages and given diet III. Litters were reduced to seven. The mothers were killed 7 weeks after the birth of the litters and these were kept together on diet in until females became pregnant¡ the mice were then separated and the same operation repeated. In the course of 18 months, five generations of mice were obtained by brother-sister breeding.
In a previous study, a very poor reproduction in rats and mice on a soybean-corn ration had been observed (4). Therefore, pregnant female mice, raised on diet In and born from mothers raised on diet In, were put on this soybean-corn ration (diet 1) which differed from diet III in that sesame meal was replaced by commercial solventextracted soybean meal. The animals and their litters were treated as described and 3 generations were raised on this diet.
The young of the experimental groups grew more slowly than the controls but the mortality was nearly the same in both groups (Table 1). Single intraperitoneal injections of 0.5 ug/animal of crystalline vitamin E12 (Merck) resulted in growth improvement for a period of 2 weeks, while 0.01 ug. was without effect (Table 1). Kidney hypertrophy has been observed in rats deficient in vitamin El2 (5,6); the ratio between body weight and weight of the kidneys in mice raised on diet III in the 3rd and 4th generation was measured and found to be 50.1 ±5.2′ in 55 adults weighing 20-32 g., while in 35 controls weighing 22-32 g. this ratio was 55.5 ±6.7.1 (For difference between means, p. < 0.01.)