Effect of dietary lipid level on growth, feed utilization and body composition of juvenile giant croaker Nibea japonica

Five isoproteic diets were designated to investigate the effects of dietary lipid levels (from 5% to 21%) on the growth performance, body composition and nutrition utilization of juvenile giant croaker, Nibea japonica (initially weighing, 6.67 +/- 0.18 g per fish). Each diet was fed to triplicate tanks (15 fish per tank) for 8-weeks. Fish fed diets with low lipid levels (5-13%) showed significantly higher weight gain (WG) and special growth ratio (SGR) than those fed high lipid diets (17-21%) (P < 0.05). A decreased trend of feed intake (Fl) and daily feed intake (DFI) was observed in Nibea japonica fed diets with lipid level from 5% to 21%. Diets with 9-13% lipid level could improve the protein utilization in this species. Fish fed diets with 5% and 9% lipid level had significantly lower viscerosomatic index (VSI), hepatosomatic index (HSI) and intraperitoneal fat ratio (IPF) than those fed with high lipid diets (13-21%) (P < 0.05). Fish fed diet with lowest lipid level showed significantly lower whole body lipid level than other treatments (P < 0.05). The liver lipid content had a trend to increase with dietary lipid level increased (P < 0.05), while liver protein and moisture level decreased with an increase in dietary lipid level (P < 0.05). Based on the second order polynomial regression analysis of WG, this study suggested that 8.22% dietary lipid level was appropriated for N. japonica. (C) 2014 Elsevier B.V. All rights reserved.