Replacing dietary methionine and cystine in chick diets with sulfate or other sulfur compounds.

A purified diet deficient in the sulfur amino acids and sulfate was fed to chicks in tests designed to compare the effectiveness of several sulfur compounds in sparing the sulfur amino acids. The addition of a mixture of methionine and cystine to this diet increased growth rate and feed efficiency more than any of the other additions. Sulfate improved performance as much as any inorganic sulfur source tested. Taurine, sulfite, thiosulfate, and sulfur also had value. When graded levels of sulfate were added to diets with sulfur amino acid levels about 0.2 and 0.3% below the level required for optimum performance, the weight gain and feed efficiency response curves were curvilinear. Most of the response to sulfate was produced with a level of 200 p.p.m., but 500 to 660 p.p.m. was needed to produce the maximum sparing effect. The sulfur amino acid requirement was found to be about 0.075% less with 0.1% sulfate in the diet than without it when growth rate was the criterion. When feed efficiency was the criterion, the requirement was reduced about 0.05% by sulfate.