Lipid nutrition of juvenile Litopenaeus vannamei II. Active components of soybean lecithin

Two experiments were conducted to investigate the active components of soyb ean lecithin for juvenile Litopenaeus vannamei. The first experiment was co nducted to determine the dietary phosphatidylcholine (PC) requirement of ju venile L. vannamei, and to investigate whether other phospholipids (PL), ma inly phosphatidylethanolamine (PE) and phosphatidylinositol (PI) were the a ctive fractions of soybean lecithin. Seven levels of PC (0%, 0.35%, 0.7%, 1 .4%, 2.1%, 2.8%, 4.2%) extracted from soybean lecithin (PC purity 93%) were used to determine the PC requirement; also, PE and PI tin a 25:22 proporti on) were tested at 0.84% and 1.68% levels with PC levels controlled at 0.35 % and 0.52% of diet to investigate the combined PE and PI effects. Results showed that no dietary PC requirement was evident based on shrimp growth an d survival. Increasing purified PC in the diet decreased total lipid, free fatty acid and other PL levels in shrimp hepatopancreas (mid-gut gland) and increased PC level in shrimp muscle. However, other FL, mainly PE and PI, showed significant enhancing effects on shrimp growth when PC was provided at 0.35% or 0.52% of diet. Another 4 X 2 factorial experiment was concluded to reevaluate the requirem ent of shrimp for PC by including purified PC at 0%, 0.7%, 1.4 % and 2.8% o f diet with or without 0.1% cholesterol in the diet. A diet containing 1.4% PC provided by deoiled lecithin also was tested for comparison. Results sh owed no interaction between PC and cholesterol on shrimp growth, survival a nd feed conversion ratio (FCR). Compared with the apparent growth-enhancing effect of dietary cholesterol, the effect of purified PC was negligible. W ith PC at 1.4% of diet, the presence of other PL from lecithin or 0.1% chol esterol significantly enhanced shrimp growth and FCR. In summary, purified soybean PC showed different effects from deoiled lecit hin on shrimp growth, lipid composition, and relationship with dietary chol esterol. Beneficial effects of soybean lecithin on growth of L. vannamei co uld be attributed to the presence of PL other than PC in the diet under the experimental conditions of this study. (C) 2000 Elsevier Science B.V. All rights reserved.