Substitution effects of fishmeal with tuna byproduct meal in the diet on growth, body composition, plasma chemistry and amino acid profiles of juvenile olive flounder (Paralichthys olivaceus)

Substitution effects of fishmeal with tuna byproduct meal (TBM) in the diet on growth, body composition, plasma chemistry and amino acid profiles of juvenile olive flounder were determined. Nine hundred fish averaging 12.6 g were randomly distributed into 30 of 180 l flow-through tanks. Ten experimental diets were prepared. A 60% fishmeal was included into the control (Con) diet. The 5, 10, 20, 30, 40, 60, 80 and 100% fishmeal were substituted with TBM at the expense of wheat flour and cellulose, referred to as the TBM5, TBM10, TBM20, TBM30, TBM40, TBM60, TBM80 and TBM100 diets, respectively. Finally, 0.37% sodium phosphate monobasic in mineral premix was replaced with cellulose in the TBM100 diet to clarify phosphorous substitution effect of TBM, referred to as the TBM100-NP diet. All experimental diets were prepared at isonitronic and isolipidic. An essential amino acid, lysine tended to decrease with an increased TBM substitution with fishmeal in the experimental diets. Weight gain and specific growth rate (SGR) of fish fed the Con, TBM5 and TBM10 diets were higher than those of fish fed the TBM40, TBM60, TBM80, TBM100 and TBM100-NP diets. Feed efficiency ratio (FER) of fish fed the Con diet was higher than that of fish fed the TBM30, TBM40, TBM60, TBM80, TBM100 and TBM100-NP diets. Protein retention (PR) of fish fed the Con diet was higher than that of fish fed the TBM30, TBM40, TBM60, TBM80, TBM100 and TBM100-NP diets. Proximate composition of fish was affected by the experimental diets. Amino acid profiles of fish were not different among the experimental diets. Plasma analysis was not different among the experimental diets. Based on these results, dietary substitution of fishmeal with up to 30 and 20% TBM could be made without adverse effect on growth (SGR) and feed utilization (FER and PR) of juvenile olive flounder, respectively.