Effects of dietary lipid levels on growth performance, plasma biochemistry, lipid metabolism and intestinal microbiota of juvenile golden pompano ( Trachinotus ovatus )

Five isonitrogenous diets were formulated containing five graded levels of lipid (52.0, 81.0, 112.0, 141.0 and 171.0 g/kg). The diets were fed to triplicate groups of juvenile Trachinotus ovatus (10.49 ± 0.23 g) for 8 weeks. Results showed that moderate lipid level in diets significantly increased weight gain rate (WGR), specific growth rate (SGR) and feed efficiency rate (FER) (p < .05). The dietary lipid level affected plasma biochemical indexes containing total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-c), total lipase (TL) and non-esterified fatty acid (NEFA) significantly (p < .05). The dietary lipid level also had significant effects on enzymatic activities including alanine aminotransferase (ALT), aspartate aminotransferase (AST), total lipase (TL), fatty acid synthetase (FAS), intestinal lipase (ILPS), adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) (p < .05). The relative level of hepatic carnitine palmitoyltransferase I (cpt1) mRNA increased significantly with increasing dietary lipid levels. The mRNA level of hepatic fatty acid synthase (fas) was significantly upregulated with dietary lipid level up to 81.0 g/kg and then decreased (p < .05). Moreover, dietary lipid level influenced microbial community to regulate metabolic capacity of intestine. The optimum dietary lipid level for the optimal growth of juvenile Trachinotus ovatus was 93.6 g/kg.