Effects of Dietary Protein Level on Growth and Body Composition of Channel Catfish Reared in Cage

Abstract

Channel catfish fingerlings (84 g) were stocked in 1.25-m³ cages at a rate of 250 fish/cage and fed to satiety once daily with diets containing 27, 32, 37, or 42% protein for 12 weeks. The diets were similar to commercial formulations, composed of soybean meal, corn, fish meal, and vitamin and mineral supplements. The protein to energy ration (P/E) was increased by substituting soybean meal and fish meal (5:1) for corn. Fish meal constituted a fixed percentage (15%) of the total protein of the diets. Growth of channel catfish fed diets with increasing dietary protein levels was not significantly different (P > 0.05) among treatments. Average final weight, total length, survival, food conversion ratio (FCR), and specific growth rate (SGR were 312 g, 31.3 cm, 84.8%, 1.47 and 1.47%/day, respectively. Protein efficiency ratio (PER) as significantly higher (P < 0.05) for fish fed a diet containing 27% protein compared to fish fed the other three diets. Dressing percentage was not significantly different (P < 0.05) among treatments and averaged 54.9%. Percentage protein in carcasses of fish fed the diet containing 27% protein was significantly lower (58.1%) compared to fish fed diets containing 32, 37, and 42% protein (61.2, 62.2, and 63.0%, respectively), whereas percentage fat was significantly higher (36.6%) than in fish fed the diet containing 37% protein (32.1%)(P < 0.05). Percentage protein and fat of waste (skin, head, and viscera) were not significantly different (P > 0.05) among treatments. The results indicate that channel catfish reared in cages can be fed a diet with 27% protein, when fed to satiation, without adverse effects on weight gain and feed conversion; however, muscle fat content was higher and protein content was lower than in fish fed higher (32, 37, and 42%) protein levels.