A Comparison of Several Amino Acid and Casein Diets for the Growing Rat

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Abstract
Weight gains and feed consumption of weanling male rats were measured when fed purified diets containing either casein or one of six different amino acid mixtures, and accompanied by variations in the level of fat as well as source of carbohydrate and salts. The casein diets (14 and 20%) were superior to any of the amino acid diets tested. The amino acid diet of Rechcigl et al. (7) containing 15.68% essential amino acids and no nonessential amino acids supported significantly better growth than the diets containing from 5.03 to 7.06% essential amino acids and nonessential amino acids to provide a total of from 12.00 to 19.45% total amino acids. Diets containing the amino acid mixture of Rama Rao et al. (8) with 12% fat and the mixture of Warner (9) supplying the lowest level of total amino acids, were inferior to the other amino acid diets tested. Similar performance was noted with diets containing the amino acid mixtures of Rechcigl et al. (6), Rama Rao et al. (8) with 2% fat, Warner (9) with a higher level of nonessential amino acids and with a diet containing a mixture of essential and nonessential amino acids intended to simulate casein. The significance of these results is discussed. There appeared to be no difference between sucrose and a dextrin-glucose mixture as the carbohydrate source or the salt mixtures of Warner (9) and Jones and Foster (16) when used in diets containing either casein or the amino acid mixture of Rechcigl et al. (6).