Effects of feeding a fish meal-free soy protein concentrate-based diet on the growth performance and nutrient utilization of red sea bream (Pagrus major)

Two groups of red sea bream (average body weight 85 g) were fed to satiation fish meal (FM) or FM-free soy protein concentrate (SPC)-based diet (FM-sat and SPC groups respectively). A third group (FM-pair) was fed the same amount of FM as of SPC fed to SPC-sat group for 6 weeks. Growth rate of SPC group was significantly slower than of FM-sat and FM-pair groups (p < 0.05). Feed conversion ratios of FM-sat and FM-pair groups were similar and were better than that of SPC group (p < 0.05). Visceral fat somatic index of SPC group was significantly lower than of the other groups (p < 0.05), while that of the latter two groups were similar. Plasma triglyceride of FM-sat and FM-pair groups was similar and lower than the level of SPC group (p < 0.05). Trypsin activity in hepatopancreas of SPC group was significantly lower than that of other groups (p < 0.05). We suggest a low growth of SPC group was not simply related to low-feed intake. Feeding of a FM-free SPC-based diet may reduce lipid accumulation and consequently lead to low-growth performance, in red sea bream.