Effect of substituting fish meal with various by-product meals of swine-origin in diet on olive flounder (Paralichthys olivaceus)

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.