Evaluation of Semipurified Test Diets for Tilapia zillii Fingerlings

An experiment was conducted to evaluate semipurified test diets for Tilapia zillii fingerlings. Four isocaloric (300 kcal dietary energy/100 g) diets containing casein (at 30 and 39%). casein supplemented with L-arginine (Arg) and casein/gelatin mixture as protein sources were fed to triplicate groups of T. zillii fingerlings at a daily rate of 3% of their body weight for 6 weeks. When casein was fed as the sole dietary protein source at 30% level, fish growth, feed conversion efficiency (FC) and protein efficiency ratio (PER) were significantly reduced. Those variables were significantly improved when casein was supplemented with Arg. The group of fish fed casein/gelatin diet showed the best growth and feed utilization. When casein was increased to 39% to meet the Arg requirement, fish growth and feed conversion were not significantly different from those of fish fed casein/gelatin diet, while PER and protein production value (PPV) were significantly reduced. These results indicated that casein/gelatin is superior to casein or casein/Arg as a protein source in semipurified test diets for T. zillii fingerlings.