Dietary protein requirement of the red drum (Sciaenops ocellatus) and relative use of dietary carbohydrate and lipid

The minimum dietary protein requirement of the red drum (Sciaenops ocellatus) was determined and its ability to utilize dietary lipid and carbohydrate was investigated in terms of growth, feed and protein efficiencies, and body composition. Six semipurified diets were formulated to contain 35, 40 or 45% crude protein from red drum muscle with similar energy: protein ratios. At each protein level, one diet contained 10% lipid while the other contained similar energy but from 3% lipid and additional dextrin. Each diet was fed to juvenile red drum in triplicate aquaria containing brackish (6 ppt) water at 23 +/- 2-degrees-C for 8 weeks. Factorial analysis of variance indicated that growth, feed and protein efficiencies were significantly (P < 0.05) affected by protein and lipid/carbohydrate levels. Fish fed diets containing 35% protein or 3% lipid at each protein level had reduced growth and feed efficiency. Highest growth and feed efficiency values were observed for fish fed diets containing 40 and 45% protein and 10% lipid. Enhanced growth and feed efficiency of fish fed diets containing 10% lipid was accompanied by increased lipid deposition in liver and peritoneal cavity. These data indicate that red drum require protein at approximately 40% of dry diet for maximum growth and that they utilize dietary lipid more efficiently than carbohydrate.