Evaluation of Fermented Soybean Curd Residues as an Energy Source in Diets for Juvenile Olive Flounder, Paralichthys olivaceus

A 10-wk feeding experiment was conducted to evaluate the potential use of fermented soybean curd residues (FSCR) as an energy source in diets for juvenile olive flounder, Paralichthys olivaceus. Five isonitrogenous and isoenergetic diets were formulated to contain dry soybean curd residues to replace wheat meal (WM) at the levels of 0, 25, 50, 75, and 100% (FSCR₀, FSCR₂₅, FSCR₅₀, FSCR₇₅, and FSCR₁₀₀, respectively). Fish averaging 6.00 ± 0.07 g (mean ± SD) were randomly distributed into 15 aquaria as groups of 15 fish and fed the experimental diets in triplicate at a rate of 4-5% of wet body weight per day twice daily on dry matter basis. At the conclusion of the feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed diet FSCR₂₅ were significantly higher than those of fish fed diets FSCR₅₀, FSCR₇₅, and FSCR₁₀₀ (P < 0.05); however, there were no significant differences in WG and SGR among fish fed diets FSCR₀ and FSCR₂₅ and among those fed diets FSCR₀ and FSCR₅₀. Feed efficiency and protein efficiency ratio of olive flounder fed diet FSCR₂₅ were significantly higher than those of fish fed diets FSCR₅₀, FSCR₇₅, and FSCR₁₀₀ (P < 0.05); however, there were no significant differences in these parameters among fish fed diets FSCR₀ and FSCR₂₅ and among those fed diets FSCR₀, FSCR₅₀, FSCR₇₅, and FSCR₁₀₀. Hematological characteristics, condition factor, hepatosomatic index, and survival rate of fish fed FSCR₀ were not significantly different from those of fish fed the other diets. These results indicated that FSCR could replace up to 50% WM as an energy source in juvenile olive flounder diets based on ANOVA test.