The Number of Vitamins Required by the Rat. ∗

Abstract

During their studies of rat dermatitis Richardson and Hogan 1 observed that rats which receive only the recognized water-soluble vitamins are able to survive for long periods of time, and to maintain a moderate rate of growth. Four of the 8 females described in Groups III and IV, Table I. of the report cited, attained an average weight of 176 g in 20 weeks, when it became necessary to discard them. The ration was then changed in various ways in an attempt to secure a more rapid growth rate and 3 of the more important modifications are described in Table I. The response of the animals is shown in Fig. 1.

It will be observed that Ration B contains no added fat, but it was supplemented with 10 mg of linoleic acid daily per rat. Ration A contains no added fat except the 2% of cod liver oil. Since neither ration supplies the quantity of fatty acids that is necessary for a normal rate of growth, even if the vitamin supply is adequate, a ration was prepared which contains additional fat. Ration C contains 8% of lard, also a more generous allowance of the water-soluble vitamins. In all 14 male and 5 female rats have received this ration and up to the present their growth rate is about the same as that of rats in the stock colony. Three males, Nos. 7385, 7391, 7392, Fig. 1, attained an average weight of 368 g in 18 weeks. They are in excellent condition and heavier than stock colony males of the same age. Each of them has sired 2 normal litters. Jukes 2 reported that a ration which contains no water-soluble vitamins, other than those now recognized, will permit female rats to attain maturity and bear litters. However, his animals grew at a subnormal rate and reared only a small proportion of their young.

The minimum amounts that will maintain normal growth have not been determined, but it is our experience that when the water-soluble vitamins are supplied at the levels commonly employed the growth rate is suboptimal. When choline was omitted from Ration C the growth rate was severely depressed. When omitted from Ration A the growth rate was unchanged.