Reducing phosphorus and nitrogen excretion in Yellowtail (Seriola quinqueradiata) nutrition: II. Effects of dietary fishmeal replacement and increasing energy level

Defatted soybean meal was replaced with fishmeal to evaluate its effect on growth and phosphorus/nitrogen excretion for young yellowtail (Seriola quinqueradiata). Soybean meal was replaced by fishmeal with the levels of 4 and 16% at 10, 16 and 20% dietary lipid level. The feeding trial continued for 80 days. Weight gain of fish significantly increased with increasing dietary lipid. Fishmeal (FM) replacement did not cause any negative effect on growth at any level of dietary lipid. Feed and protein efficiencies slightly decreased with increased level of FM replacement. Both parameters significantly (P<0.05) improved with increasing dietary lipid. No significant interaction was determined between dietary lipid and SBM level on the any measured parameter. P and N excretion significantly (P<0.05) decreased with increasing dietary lipid. In conclusion, based on growth and P/N excretion data, 10% FM replacement by defatted soybean meal with 20% lipid from the diet containing 43% protein could be recommended to obtain superior results considering decreasing detrimental effect of P and N to the environment in yellowtail nutrition weighing from ~420 g to ~900 g.