effect of different levels of dietary phospholipid on growth, survival and nutrient composition of early juvenile cobia (Rachycentron canadum)

This experiment was conducted to evaluate the effect of different levels of dietary phospholipid (PL) on growth, survival and nutrient composition of 25 days posthatch cobia Rachycentron canadum (0.4 g initial wet weight). For 42 days, fish were fed fish meal and protein hydrolysate based diets containing four PL levels (0, 20, 40 and 80 g kg⁻¹dry matter: purity 97%) and phosphatidylcholine purity was 60%. All diets were isonitrogenous and isolipidic by regulating the fish oil and maize oil levels. Weight gain (2601-10892%), specific growth ratio (7.82-11.18) and survival (49-100) were significantly affected by dietary PL. Intraperitoneal fat ratio (0.19-0.74) and hepatosomatic index (2.67-3.08) increased with dietary PL level. The effect of dietary PL levels on the chemical composition of tissues was significant only for whole body and liver. The contents of plasma total cholesterol (2.47-3.77 mmol L⁻¹) and PL (1.03-2.97 mmol L⁻¹) increased with an increase in dietary PL. In conclusion, in our study survival and growth continued to increase even at the highest PL levels used (80 g kg⁻¹); therefore optimal dietary PL levels may well exceed 80 g kg⁻¹ for early juvenile cobia requirement. It also indicated from the experiment that PL could affect lipid deposition and resulted in a higher lipid level in fish tissue.