The Relationship of Choline and Cystine to the Methionine Requirement of Young Chickens ,

THE essential nature of methionine in the diet of the chick was demonstrated by Klose and Almquist (1941). Homocystine and choline together effectively replaced methionine in the diet of the chick, but neither homocystine nor cystine completely replaced methionine. Direct proof of the homocystine-choline-methionine interrelationship in the rat was presented by Simmonds et al. (1943). Transmethylation was observed both in the absence of homocystine and in the presence of ordinary methionine when the diet contained deuterio-choline. Du Vigneaud et al. (1944) reported results which demonstrated the role of methionine in cystine formation. Grau and Almquist (1943) investigated the relationship between the sulfur amino acids and choline in chick nutrition. Choline-depleted chicks were able to utilize homocystine effectively in the place of cystine but not as a substitute for methionine. Almquist and Grau (1945), using a diet deficient in methionine and cystine, fed increasing levels of cystine up to 0.9 percent . . .