Evaluation of Dietary Lipid Requirement of Juvenile Giant Grouper, Epinephelus Lanceolatus (Bloch) by Supplement with Different Levels of Fish Oil or Soybean Oil in Fish Meal Basal Diet

This study was conducted to determine the dietary lipid requirement of juvenile giant grouper, Epinephelus lanceolatus by using fish oil or soybean oil in a fish meal basal diet (fish meal contributes 5.6% of lipid content). No negative impact on growth performance of fish was recorded in both of fish oil-or soybean oil-supplemented diets. Based on the feed efficiency, fish fed the diets with 12% to 16% lipid contents for 56 days in fish oil groups or soybean oil groups had significantly better feed utilization as compared to that of fish fed the diets with 8% and 10% lipid contents. At the end of the experiment, no significant differences in survival, hepatic somatic index, and protein content and moisture in dorsal muscle were recorded. Liver and dorsal muscle fatty acid composition clearly reflected the fatty acid composition in test diets. Linoleic acid (C18:2n-6) deposition in liver and dorsal muscle was significantly increased in soybean oil groups as compared to that of in fish oil groups. Decreases in eicosapentaenoic acid and docosahexaenoic acid deposition in liver and dorsal muscle were recorded in soybean oil groups as compared tothose of in fish oil groups. This study indicated that the optimal dietary lipid level in juvenile giant grouper is about 12%, and soybean oil could be supplied in a fish meal basal diet in which fish meal contributes 5.6% of lipid content.