Effect of the dietary phosphatidylcholine at different growth stages of Pacific white shrimps, Litopenaeus vannamei

This study investigated the effects of dietary phosphatidylcholine (PC) at different growth stages of Litopenaeus vannamei (L. vannamei) with an initial weight of 0.70 +/- 0.00 g (juvenile) and 4.25 +/- 0.00 g (subadult) for 8 weeks. Six isonitrogenous and isoenergetic diets containing PC (0, 1.7, 5.1, 6.8, 10.2 and 13.6 g/kg) were confected using formulated with redfish meal, dehulled soybean meal and peanut meal as protein source, fish oil and corn oil as fat source. The juveniles were reared in 0.3 m(3) aquarium at the density of 40 in triplicates, as well as the subadults in 0.5 m(3) at the density of 40 in triplicates. Results showed PC level had significant effects on weight gain rate (WGR), specific growth rate, feed conversion ratio in juvenile and subadult shrimps and hepatosomatic index in juvenile shrimps (p < 0.05). No significant differences were found in moisture, whole body protein and crude ash (p > 0.05). Crude fat of juveniles had no significant change (p > 0.05), but subadults increased significantly (p < 0.05). Both juveniles and subadults showed that triglyceride and low-density lipoprotein presented a downward trend with PC elevating, but high-density lipoprotein increased gradually. Cholesterol in juveniles presented upward, but downward in subadults (p < 0.05). Dietary PC also significantly reduced the aspartate transaminase in juveniles and alanine transaminase in subadults (p < 0.05). PC supplementation significantly improved the glutathione S-transferase activity and reduced the content of malondialdehyde in the hepatopancreas (p < 0.05). PC supplementation significantly improved gill filament sodium-potassium adenosine triphosphatase enzyme of juvenile shrimps (p < 0.05), but subadult shrimps were not influenced (p > 0.05). PC supplementation significantly elevated the content of hepatopancreas eicosapentaenoic acid, highly unsaturated fatty acid (HUFA) and n-3HUFA (p < 0.05), but the content of linoleic acid significantly reduced (p < 0.05). The broken-line and quadratic regression model based on WGR showed the optimum dietary PC requirement was 10.3 g/kg and 6.5 g/kg for juveniles and subadults, respectively.