Enzymatic tuna hydrolysate supplementation modulates growth, nutrient utilisation and physiological response of pompano (Trachinotus blochii) fed high poultry-by product meal diets

Six experimental diets were prepared in a 3 × 2 experimental design involving three inclusion levels (0%, 50%, and 100%) of poultry by-product meal (PB) and two concentrations (0 and 60 mg/kg) of tuna hydrolysates (TH), labelled as PB0, PB0TH, PB50, PB50TH, PB100, and PB100TH, respectively. The diets were fed to juvenile pompano for 10 weeks to investigate the nutritional value of PB in conjunction with TH supplementation on growth, feed efficiency, biochemical composition, haematological and histological responses in the species. The results indicated that the final body weight, specific growth rate, and feed conversion ratio were negatively affected by the increasing replacement of fishmeal by dietary poultry by-product meal with or without TH supplementation compared to the control (P<0.05). A significant (P<0.05) reduction of whole-body protein was recorded in the PB100 diet while body lipid and ash levels neither increased nor decreased either by replacement levels or TH supplementation. Except for serum albumin and triglycerides, all other serum parameters were not influenced by PB diets supplemented with tuna hydrolysate (P ˃ 0.05). The histopathological alterations in the liver were appeared in fish fed PB50, PB100, and PB100TH diets. Fish fed fishmeal replacement diets showed reduced methionine, lysine, threonine, and valine contents compared to control (P < 0.05). Overall, this study demonstrates that fish fed non-fishmeal diets showed significantly lower growth and feed efficiency than those fed control diet, irrespective of tuna hydrolysate supplementation