Sulfur Amino Acid Activity of d- and l-Homocysteine for Chicks

Young male chicks were fed crystalline l-amino acid diets in assays designed to evaluate the capacity of d-and l-homocysteine to supply methionine and cysteine. l-Homocysteine had a cystine-sparing value of 100% and a methio-nine-sparing value of 28% at the level fed. d-Homocysteine was utilized less efficiently than was l-homocysteine, having a cystine-sparing value of 68% and a methionine-sparing value of only 7%.