The optimal dietary lipid level for golden pompano Trachinotus ovatus fed the diets with fish meal replaced by soy protein concentrate

A feeding trial was conducted to determine the optimal dietary lipid level for golden pompano Trachinotus ovatus and the effect of dietary lipid level on fish meal replacement with soy protein concentrate (SPC). Eight isonitrogenous diets were formulated to contain four lipid levels (65 g/kg, 85 g/kg, 105 g/kg and 125 g/kg) and two fish meal levels (280 g/kg and 140 g/kg) respectively. Fish (initial weight 25.2 ± 0.5 g) were fed the test diets in net pens for 7 weeks. At the same dietary fish meal level, weight gain and nitrogen retention efficiency (NRE) tended to increase, while feed intake, feed conversion ratio (FCR) and nitrogen waste tended to decrease, with elevating dietary lipid level from 65 g/kg to 105 g/kg. At the same dietary lipid level, no significant differences were found in weight gain, feed intake, FCR, NRE, condition factor, hepatosomatic index, proximate composition and nitrogen waste between fish fed the diets containing 280 g/kg and 140 g/kg fish meal. This study reveals that the optimal dietary lipid level for golden pompano should be 107 g/kg, and dietary fish meal level could be reduced to 140 g/kg by using SPC as a fish meal substitute. Elevating dietary lipid level could not significantly increase fish meal replacement level with SPC.