Yeast as a source of vitamine-B for the growth of rats

Abstract

Yeast is commonly considered the richest source of vitamine-B for the growth of young animals. We have fed groups of rats in colonies on a basal diet of purified casein 18 per cent., salts 3.7 per cent., agar 2 per cent., butter fat 5 per cent., with dextrin to make 100 per cent., and have supplied the vitamine-B in the form of dried yeast of various sources, both as an integral part of the diet or separately in the form of a tablet. Our results were as follows:

Air-dried Fleischmann's baker's yeast containing 40 per cent. yeast in the dried product failed to produce normal growth in all cases when the ration contained 4 per cent. or less of the dried product and certain individuals even failed to make normal growth when the dried yeast formed 10 per cent. of the diet. Out of 20 rats, 9 were females, and none of these produced young during the 2 to 4 months of the experiment.

When the same yeast was fed separately, 0.6 gram per day per rat was required to secure normal growth. Two out of 4 females on this diet produced young (total of 3 litters) but all the young were destroyed by the mothers.

A dried brewer's yeast prepared by us from a wet mixture of bottom yeast and wort secured from a local brewery produced only about one-half normal growth when fed as high as 10 per cent. of the diet, but when these rats were transferred to a mixed diet of grains and milk their growth curves rose sharply towards the normal. When the same yeast was fed separately to other rats at the rate of 0.2 and 0.4 gram per day per rat the results were little better than when the yeast was incorporated in the diet at the rate of 10 per cent. There was no reproduction.