Abstract
Rats fed purified rations containing 24% protein in the form of a soybean protein preparation and dl-methionine as the only source of amino acids made satisfactory post-weaning weight gains for 4 successive generations. Extensive purification of the soybean protein did not decrease the growth rate of rats consuming this protein as compared to that of animals consuming a less purified preparation. Daily administration of 0.25 μg of crystalline vitamin B12 to rats on a ration containing a highly purified soybean protein preparation did not increase the early post-weaning weight gains or the efficiency of food utilization.