Crystalline Amino Acid Diet Supplemented with Gelatin, Sulfate, Methionine and Fishery Products

Four experiments were conducted to investigate the nutritional value of inorganic sulfate in comparison with methionine and fishery products in chemically defined basal diets containing crystalline amino acids supplemented with mineral mixture free of sulfate compounds. All diets contained 5% level of gelatin to supply the need of intact protein. Dietary inorganic sulfate supplementation increased chick growth, but not significantly (P < 0.05), when the methionine content of the crystalline amino acid diet was extremely low (0.2%). Sulfate additions improved growth slightly but significantly when the methionine content was 0.35 or 0.40% and very pronouncedly when it was 0.50% but not when the content was 0.60% or 0.90%. These higher levels of methionine were evidently adequate and therefore the sulfate supplement was ineffective to produce a growth response. These results suggested that the sulfate may be a partial substitute for methionine when the latter was present at inadequate dietary levels but there was no indication of a specific nutritional need for preformed sulfate. The existence of unknown growth factor (UGF) in fishery products was demonstrated by the increase in growth above that obtained by the inorganic sulfate or methionine although each amino acid was maintained at a constant level in all diets.