Sequence in Which the Amino Acids of Casein Become Limiting for the Growth of the Rat

Abstract

In an effort to determine the sequence in which the amino acids of casein become limiting for the growth of young rats, feeding experiments were conducted using diets containing sucrose or dextrin and 6% of casein supplemented with various amino acid mixtures. From the results of these experiments it was concluded that the sulfur-containing amino acids are most limiting; threonine next; then tryptophan, isoleucine, leucine, histidine, valine and phenylalanine all about equally limiting; lysine slightly less so than the preceding 6; and finally arginine, least limiting. A mixture of all of these together with glutamic acid was required with 6% of casein to support a rate of gain of young rats equivalent to that obtained with comparable rats fed an adequate purified diet. A number of the amino acid mixtures caused imbalances or antagonisms which resulted in growth retardation.