Assessment of the essentiality of methionine, threonine, tryptophan, histidine and isoleucine in immature dogs.

A completely purified L-amino acid diet was used to evaluate the indispensability of methionine, threonine, tryptophan, histidine and isoleucine in the immature dog. Immature dogs fed diets devoid of methionine, threonine, tryptophan, histidine or isoleucine had severely depressed food intakes, accompanying weight loss, and a distinctly negative nitrogen balance. Partial or total removal of these amino acids resulted in a marked increase in blood and urinary urea. Estimates are made for the dietary requirements for these amino acids in the immature dog.