Sequence in which the amino acids on corn (Zea mays) become limiting for growing rats

Three 21-day feeding experiments were conducted to determine the sequence in which the amino acids of corn become limiting for the growth of young rats. Diets consisted of corn fortified with minerals and vitamins, and supplemented with various combinations of essential amino acids. On the basis of improvements in growth rate and feed efficiency, the sequence of limiting amino acids in corn was determined to be: (1st) lysine and tryptophan--colimiting, (3rd) threonine, (4th) isoleucine, (5th) valine, (6th) methionine, and (7th) possibly histidine and phenylalanine--colimiting. Changes in blood urea levels generally confirmed this sequence. There was no limitation of either arginine or leucine, or of nonspecific nitrogen. Weight gains and feed efficiencies of rats fed a corn diet supplemented with the eight limiting amino acids were equivalent to published values for rats fed nutritionally adequate diets.