Substitution effect of fish meal with meat meal in diet on growth performance, feed consumption, feed utilization, chemical composition, hematology, and innate immune responses of rockfish (Sebastes schlegeli)

Fish meal (FM) is widely used as a main protein source in formulated feed for marine fish culture. However, the production of FM has shrunk or plateaued due to the overfishing and climate change in the wild. Meat meal (MM) is known as a good replacer for FM in fish feeds. Dietary replacement effect of MM for FM on the growth, feed consumption, feed utilization, body composition, hematology, and innate immune responses of rockfish was determined. A total of 630 fish (initial weight of 2.3 g) was randomly distributed into 21, 50 L flow-through tanks (30 fish/tank). Seven experimental diets were formulated. The control (MM0) diet contained 55% FM. Then, 10, 20, 40, 60, 80, and 100% FM in the MM0 diet were replaced with MM, referred to as the MM10, MM20, MM40, MM60, MM80, and MM100 diets, respectively. All experimental diets were allocated to triplicate groups of fish. Fish were hand-fed to visual satiation twice a day for 8 weeks. Increased substitution of FM with MM in diets resulted in decreased essential amino acids (EAA), such as lysine and threonine and the sum n-3 highly unsaturated fatty acids, but increased EAA, such as arginine and methionine, and the sums of saturated and monoene FA. Weight gain (9.8 g/fish) of fish fed the MM10 diet was significantly (P < .003) greater than that (8.8, 8.9, 8.2, and 7.9 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Specific growth rate (SGR) (2.93%/day) of fish fed the MM10 diet was significantly (P < .004) higher than that (2.79, 2.69, and 2.64%/day, respectively) of fish fed the MM0, MM80, and MM100 diets. Weight gain and SGR of fish fed the MM100 diet were (P < .05) significantly lower than those of fish fed the MM0 diet. Feed consumption (9.34 g/fish) of fish fed the MM10 diet was significantly (P < .002) higher than that (8.72, 8.59, 8.32, and 8.10 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Feed efficiency (1.04%) of fish fed the MM10, MM40, and MM60 diets was significantly (P < .009) higher than that (0.99, and 0.98%, respectively) of fish fed the MM80, and MM100 diets. Condition factor, protein efficiency ratio, protein retention, hematological parameters, and innate immune responses (lysozyme and superoxide dismutase activities) of fish was not significantly (P > .05) different among the experimental diets. The chemical composition, and AA and FA profiles of the whole-body fish were not influenced by the experimental diets. In conclusion, dietary substitution FM up to 80% with MM can be made without deteriorating growth performance of rockfish. However, the optimum substitution level of FM with MM in diets were estimated to be 18.5, and 18.2% based on regression analysis of weight gain and SGR of rockfish, respectively.