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The increased global market value of fish meal (FM) and the overfishing of wild fishery resources have boosted efforts to identify protein sources that can be cheaply and reliably supplied as an alternative to FM, which is commonly used as a main protein source in fish diets. Numerous studies over the years have demonstrated that animal by-product meals are the effective alternatives for FM in fish diets. This study aimed to elucidate the effect of substituting FM with various by-product meals of swine-origin in diet on growth, feed utilization, chemical composition, plasma biochemical parameters, and superoxide dismutase (SOD) and lysozyme activity of juvenile olive flounder (P. olivaceus). All experimental diets were formulated with five isonitrogenous (56.5%) and isolipidic (10.0%) diets. The control (Con) diet included 65% FM and 12% dehulled soybean meal as the protein sources and 4.2% fish oil as a lipid source. Thirty percent of FM was replaced with plasma powder, heme powder, globin powder, and pork greaves meal, named as the PP, HP, GP, and PM diets, respectively. Three hundred and seventy-five juvenile (9.2 ± 0.01 g; mean ± SD) fish were placed into 15 flow-through tanks with three replicates. Fish were carefully hand-fed to apparent satiation twice a day for 56 days. At the end of the feeding period, weight gain and specific growth rate of fish fed the GP and PM diets were comparable to fish fed the Con diet. Feed consumption of fish fed the PP, GP, and PM diets was comparable to fish fed the Con diet. Feed utilization and condition factor of fish fed the HP diet were the lowest. Plasma biochemical parameters, chemical composition, amino acid profiles, and SOD and lysozyme activity of fish were unaffected by dietary treatments. Thus, GP and PM are the appropriate replacers for FM in the olive flounder diets, wherein 30% FM is substituted by diverse by-product meals of swine-origin.

This study aims to reveal the substitution impact of fish meal (FM) with the combined meat meal and chicken by-product meal (CMC) in the olive flounder (P. olivaceus) feeds on growth and feed availability. Seven experimental feeds were formulated. The control (CMC0) diet included 65% FM. In the CMC0 diet, the various (10%, 20%, 40%, 60%, 80%, and 100%) levels of FM were replaced with CMC, named as the CMC10, CMC20, CMC40, CMC60, CMC80, and CMC100 diets, respectively. The total number of 525 juvenile fish (9.2 ± 0.01 g; mean ± SD) was placed into 21 50-L flow-through tanks (25 juveniles/tank) with three replicates. Fish were hand-fed to apparent satiation for 8 weeks. After the 8-week feeding experiment, olive flounder fed the CMC10 (40.0 ± 0.60 g/fish, 2.99 ± 0.021%/day, and 39.57 ± 0.542 g/fish; mean ± SD), CMC20 (47.3 ± 2.58 g/fish, 3.24 ± 0.082%/day, and 45.16 ± 0.760 g/fish), and CMC40 (40.2 ± 1.17 g/fish, 3.00 ± 0.040%/day, and 39.43 ± 0.930 g/fish) diets attained superior (p < 0.0001 for all) weight gain, specific growth rate (SGR), and feed consumption compared to olive flounder fed the CMC0 (35.1 ± 0.96 g/fish, 2.81 ± 0.039%/day, and 33.75 ± 0.544 g/fish), CMC60 (31.7 ± 1.62 g/fish, 2.66 ± 0.068%/day, and 31.60 ± 1.080 g/fish), CMC80 (24.7 ± 0.63 g/fish, 2.33 ± 0.033%/day, and 25.27 ± 0.689 g/fish), and CMC100 (17.8 ± 0.32 g/fish, 1.92 ± 0.021%/day, and 18.99 ± 0.592 g/fish, respectively) diets. Weight gain, SGR, and feed consumption of olive flounder fed the CMC60 diet were comparable to olive flounder fed the CMC0 diet. Feed efficiency and protein efficiency ratio of olive flounder fed the CMC60 diet (1.02 ± 0.007 and 1.79 ± 0.034) were comparable to fish fed the CMC0 diet (1.04 ± 0.012 and 1.85 ± 0.021, respectively). None of the plasma and serum measurements, proximate composition, amino acid profiles, or survival of olive flounder after S. iniae infection were influenced by dietary treatments. In conclusion, CMC can substitute FM up to 60% (39% FM protein in the diet) without deteriorating growth performance, feed availability, or the survival of fish after S. iniae infection.