Effects of dietary lipid level on growth, fatty acid composition, digestive enzymes and expression of some lipid metabolism related genes of orange-spotted grouper larvae (Epinephelus coioides H.)

A 4-week. study was conducted to investigate; the; effects of dietary lipid level on growth, fatty acid composition, activities of digestive enzymes and some lipid metabolism related genes of orange spotted grouper larvae (Epinephelous coioides). Six isonitrogenous (57% crude protein) diets were formulated to contain graded contents of lipid (5.94%, 9.92%, 13.30%, 17.71% and 21.87% dry weight, respectively) using fish oil as main lipid source. Each diet was fed six times daily to triplicate groups of fish (71 +/- 2 mg, 29 DAH). Results showed that the highest SCR and survival of larvae occurred in 17.71% and 11.30% lipid group respectively The optimal dietary lipid requirement. of larval grouper was estimated to he 15.99% based on SGR. Activities of pepsin and lipase were significantly higher in 17.71% lipid group compared to the rest ones. However, the highest activities of trypsin and amylase occurred in 9.92% and 5.94% lipid treatment respectively. The expression of fatty acid synthesis (FAS) decreased significantly with increasing dietary lipid, while the expression of lipoprotein lipase (LPL) and hormone sensitive lipase (11810 significantly increased first and then decreased significantly. Compared to other treatment, larvae fed diets with 13.10% and 17.71% lipid have a significant higher relative expression of LPL and HSL respectively. Results of this study suggested that larvae fed the diet with appropriate lipid content showed higher growth performance. Moreover, dietary lipid content could also influence both de non, lipogenesis and lipolysis transcriptional level.