A 56‐day feeding trial was conducted to investigate the effects of substituting fish meal (FM) with combined tuna by‐product meal and corn gluten meal (TC) at substitution levels of 25% and 50%, with or without 24% jack mackerel meal (JMM), on the growth, feed consumption (FC), feed utilization, blood chemistry, biochemical composition, and economic efficiency of red sea bream ( Pagrus major ). A total of 375 juveniles were allocated to 15, 50‐L flow‐through tanks (25 fish per tank) to evaluate five experimental diets that were formulated to be isoproteic and isolipidic in a triplicate group. A two‐way ANOVA FM substitution levels (FMSL, 25% and 50%) × JMM inclusion (without and with) experimental design was implemented. The control diet (Con) was comprised of 60% FM. In the Con diet, 25% and 50% of FM were substituted with TC, without and with JMM inclusion at these levels, designated as the TC25, TC50, TC25J, and TC50J, respectively. Fish were hand‐fed to apparent satiation. The 25%‐FM substitution diets resulted in significantly ( p 0.05) affected by either FMSL or JMM inclusion. The 25%‐FM substitution diets led to significantly ( p < 0.048) higher total monounsaturated fatty acid (∑MUFA) in the whole‐body fish than the 50%‐FM substitution diets. The 25%‐FM substitution diets also led to significantly ( p < 0.011) higher economic profit index (EPI) than the 50%‐FM substitution diets. In conclusion, TC exhibits the potential to replace up to 50% of FM in the diet of red sea bream, regardless of JMM inclusion, without adversely impacting WG, SGR, FC, feed utilization, biological indices, proximate composition, amino acid profile, and economic sustainability. However, the TC25J diet is recommended as the most effective strategy for achieving optimal growth performance and FC and maximum EPI.
Hasan et al. (2026) studied this question.