The addition of fresh beef or of a meat scrap to a wheat-milk diet, used as a breeding colony ration for white rats, improved reproduction, and the growth rate and general vigor of the young as compared with the performance on the wheat-milk diet. The use of dried yeast with the wheat-milk diet caused a slight improvement in reproduction but the growth rate and general vigor of the young were not bettered. The improved performance on the wheat-milk diet supplemented with fresh beef or with meat scrap cannot be due chiefly to an increase in calcium and phosphorus or to an increase in the Ca:P ratio.