Inclusion of Jack Mackerel Meal in Low‐Fish Meal Diets: Impacts on the Growth and Feed Utilization of Red Sea Bream ( Pagrus major ) and Economic Analysis

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Combined animal and plant sources can replace higher levels of fish meal (FM) in fish feeds than a single source, as they compensate for the nutritional imbalances and deficiencies inherent to individual protein sources. Nevertheless, low‐FM diets often exhibit deteriorated palatability and reduced feed intake, ultimately leading to retarded growth. This experiment, therefore, aims to assess inclusion impacts of jack mackerel meal (JMM) in low FM diets substituting various levels of FM with combined meat meal (MM) and corn gluten meal (CGM) (MC) on the growth and feed utilization of red sea bream ( Pagrus major ) and economic analysis. A two‐way (FM substitution level [SL] [25% and 50%] × JMM inclusion [without or with]) ANOVA experimental design was adopted. A total of 375 juvenile (initial mean weight of 2.0 g) fish were randomly distributed into 15 flow‐through tanks. The control (Con) diet included 60% FM. In the Con diet, 25% and 50% of FM were substituted with MC, and then 24% JMM was included at the cost of FM, named the MC25, MC50, MC25J, and MC50J diets, respectively. All experimental feeds were formulated to be isoproteic (52.0%) and isolipidic (15.0%). The experimental diets were offered to fish twice daily until apparent satiation over an 8‐week period. The diets with 25% of FM substitution achieved higher weight gain (WG), specific growth rate (SGR), and feed consumption (FC) in fish than those with 50% of FM substitution. Furthermore, WG, SGR, and FC of fish fed the MC‐substituted diets with JMM inclusion were superior to those without JMM inclusion. The highest WG, SGR, and FC were attained in fish fed the MC25J diet. The MC25J diet showed the highest economic profit index (EPI), although no significant difference was detected among dietary treatments. In conclusion, the MC25J diet appears to represent the best feeding strategy to enhance the growth performance and FC in red sea bream and maximize EPI to farmers.