Effects of dietary protein concentration on growth and muscle composition of juvenile Zacco barbata

Abstract

The effects of dietary protein concentration on growth and muscle composition of juvenile Zacco barbata were investigated using white fish meal as the major protein source. Six experimental moist diets containing 20.5 to 45.3% protein were fed to triplicate groups of 16 fishes (0.338 ± 0.002 g) for 10 weeks. There was no mortality among test fishes throughout the experiment. Specific growth rates and feed conversion ratios for fish fed diets containing 30.7, 35.2, 40.9, and 45.3% protein were better (P < 0.05) than those fed diets containing 20.5 and 25.8% protein. Fish fed 35.2, 40.9, and 45.3% protein diets excreted more (P < 0.05) ammonia than fish fed diets containing 20.5 and 25.8% protein. Fish on the lowest protein diet (20.5%) showed the highest protein efficiency ratio. Fish fed high-protein diets had higher protein and ash content in their muscle. Whereas, fish fed high-protein diets had lower lipid content in muscle than those fed low-protein diets. Analyzed by a broken-line model with final body weight as the indicator, the optimal dietary protein level for Z. barbara is approximately 32.0 ± 0.1%.