Effects of Dietary Supplement of Schizochytrium Meal on Growth, Fatty Acid Profile and Activities of Digestive Enzymes in Turbot (Scophthalmus maximus L.) Larvae

A feeding trial was conducted to investigate the effects of supplementation of Schizochytrium meal on growth, digestive enzymes activities and fatty acid composition of turbot (Scophthalmus maximus L.) larvae. Four isonitrogenous and isolipidic diets were formulated to contain 0 (S0, control diet), 50 (S5), 100 (S10) and 150 (S15) g kg(-1) Schizochytrium meal. Fish (initial body weight, 0.06 g) were randomly allotted to 12 square fiberglass tanks. Fish were fed 5 times daily (7:00, 10:00, 14:00, 17:00 and 21:00) for 28 days. No significant differences were observed in survival and intestinal morphology among fish fed various levels of algae meal (P>0.05). Fish fed diet S5 had significantly higher final body weight than that of fish fed diet S15, and no significant differences were observed among fish fed diets S0, S5 and S10 (P>0.05). Trypsin in intestinal segments, specific activities of alkaline phosphatase (AKP) in intestine and purified brush border membrane (BBM) of intestine were significantly higher in fish fed diet S5 than that of fish fed diet S15 (P<0.05). Specific activities of leucine-aminopeptidase (LAP) in intestine and purified BBM of intestine was significantly higher in fish fed diet S10 than that of fish fed diet S15 (P<0.05). Fish fed diets S5 and S10 had significantly higher docosahexaenoic (DHA, 22:6n-3), n-3 PUFAs content and n-3/n-6 ratio in muscle than fish fed diets S0 and S15 (P<0.05). Fish fed diets S5, S10 and S15 had significant lower C18:3n-3, eicosapentaenoic (EPA, 20:5n-3), C18:2n-6, n-6 polyunsaturated fatty acids (PUFAs) content in muscle than fish fed the control diets (P<0.05). No significant differences were observed in intestinal morphology (P>0.05). In conclusion, 50-100 g kg(-1) dry matter Schizochytrium meal in microdiets can improve growth performance and may be a valuable additive in microdiets of turbot larvae.