TOTAL SULFUR AMINO-ACID REQUIREMENT OF JUVENILE RED DRUM, SCIAENOPS-OCELLATUS

Two experiments were conducted in a brackish water (6 +/- 1 ppt) recirculating system to quantify the total sulfur amino acid requirement of juvenile red drum (Sciaenops ocellatus) and the replacement value of cystine for methionine. The experimental diets contained 35% crude protein from red drum muscle, shrimp metal and crystalline amino acids. Incremental levels of L-methionine were added to the basal diet in the methionine experiment and fed to juvenile red drum for 8 weeks. Based on growth and feed efficiency data, the total sulfur amino acid requirement was determined to be 1.06% of diet (3.03% of dietary protein). In the second experiment to determine the replacement value of cystine for methionine, diets were formulated to contain 0.95% total sulfur amino acids with various percentages provided by cystine and methionine. Based on growth and feed efficiency of red drum fed the various diets for 5 weeks, cystine was able to spare approximately 40% of the dietary methionine requirement on an equimolar sulfur basis without significantly reducing performance. Results from these experiments provide information that will assist in formulating diets to satisfy the sulfur amino acid requirement of red drum.