Abstract:Four isonitrogenous, isoenergetic, and isolipidic diets with varying ratios (0 : 6, 2 : 4, 4 : 2, and 6 : 0) of concentrated soybean phospholipid oil (P) to refined rapeseed oil (R) (P0R6, P2R4, P4R2, and P6R0) were formulated to determine the suitable ratio of soybean phospholipid oil to rapeseed oil in the diet of juvenile large yellow croaker (Larimichthys crocea). Each diet was randomly assigned to triplicate sea floating cages of 40 fish [initial body weight (20.84±0.05) g]. Fish were fed to apparent satiation twice daily (5:30 and 16:00) over 51 d. The results suggested that the survival rates of tested fish were higher than 91%, with no significant differences among treatments (P>0.05). The special growth rate was significantly higher with fish fed P2R4, compared with those fed P4R2 and P6R0 (P<0.05). Higher lipid and protein deposition rates were found in P2R4-fed fish compared with those fed the other treatments (P<0.05). Contents of crude protein in whole body and muscle were not significantly affected by the ratio of soybean phospholipid oil to rapeseed oil in diets (P>0.05), but were significantly higher in the viscera of P0R6-fed fish compared with the other treatments (P<0.05). Concentrations of crude lipid in the whole body of P0R6- and P2R4-fed fish were significantly higher than those in P4R2-and P6R0-fed fish (P<0.05). The fatty acid profile of the whole body and muscle was similar to that of the fed diet. The ratio of soybean phospholipid oil to rapeseed oil in diets had no significant effect on hepatosomatic index and viscerosomatic index (P>0.05). The P6R0 diet significantly reduced the liver lipid content and condition factor of test fish (P<0.05). Under the conditions of this study, the suitable ratio of concentrated soybean phospholipid oil to refined rapeseed oil in the diets of juvenile large yellow croaker was 2 : 4, based on growth performance, body composition, and fatty acid composition.
