Sulfur utilization by the chick with emphasis on the effect of inorganic sulfate on the cystine-methionine interrelationship
Sasse, C.E.; Baker, D.H.
Journal of Nutrition 104(2): 244-251
1974
ISSN/ISBN: 0022-3166 PMID: 4810986 Document Number: 77863
Cystine was included in the purified diets given to chicks to provide 0, 20, 40, 50, 60 or 70% of the total S-containing amino acids (SAA), the balance coming from methionine. The diets were given without or with 0.1% K2SO4. When SAA were at or near adequacy, the optimum percentage from cystine was 48.4% in the presence of K2SO4 and 52.7% in its absence. When the diet was deficient in SAA, optimum performance occurred when cystine supplied 41.3 and 48.2% of the SAA need, respectively, in the presence and absence of K2SO4. Results for body composition confirmed that the response to inorganic sulphate was not the result of water retention but instead of increased retention of protein and energy. An assay was conducted to compare 0.10% K2SO4 with quantities of taurine and cysteine, to supply the same amount of S, when added to a sulphate-free diet first limiting in cysteine. Chicks given K2SO4 or cysteine gained more weight than those on the basal diet, but there was no response when taurine was given. Gain responses to S sources could be explained entirely on the basis of food intake.