The nutritional value of dietary n-3 and n-6 fatty acids for the Chinese prawn (Penaeus chinensis)

Triacylglycerides of highly purified n-3 and n-6 fatty acids (18:2n-6, 18:3n-3, 20:4n-6 and 22:6n-3) were each added separately at 1% to a basal diet which contained 4% of an equal mixture of tripalmitin and triolein to make four experimental diets with a control diet which contained 5% of the 16:0 and 18:1n-9 mixture as the only lipid. Each diet was fed to replicate groups of juvenile Chinese prawn (Penaeus chinensis) for 32 days. The prawn fed the control diet without supplemental n-6 or n-3 fatty acids showed poor growth and survival. The addition of 1% of 18:2n-6, 18:3n-3 or 20:4n-6 to the basal diet significantly improved weight gains (P<0.05), while the additions of 18:3n-3 or 20:4n-6 also significantly improved survival rate and molting frequency. The prawn fed the diet containing 1% 22:6n-3, however, exhibited the highest survival rate, molting frequency and weight gain among the five diets (P<0.01). The results indicate that both n-6 and n-3 fatty acids have essential fatty acid (EFA) value to the Chinese prawn, and that the EFA value increases in the order 18:2n-6<18:3n-3≤20:4n-6<22:6n-3.