Investigating suitable dietary lipid content for mandarin fish (Siniperca chuatsi), on the basis of growth, lipid metabolism, antioxidant capacity and flesh texture

This study was designed to figure out suitable dietary lipid level for mandarin fish (Siniperca chuatsi). Five isonitrogenous diets with different lipid content (6 %, 9 %, 12 %, 15 %, and 18 %, named L6.72, L9.43, L12.09, L15.87, L18.04, respectively) were manufactured to feed the experimental mandarin fish (102.59 ± 0.07 g) twice daily. The five experimental groups each had three replicates, containing 30 mandarin fish. The feeding trail lasted for 56 days. The results revealed increasing dietary lipid content linearly increased the feed intake (FI), final body weight (FBW) and specific growth rate (SGR) of cultured fish. In addition, the crude lipid content in the whole body, liver and muscle of mandarin fish also significantly increased. The total superoxide dismutase (T - SOD) activity in the L12.09 group showed the highest value and the malondialdehyde (MDA) content in the L12.09 group was the lowest. The serum biochemical indexes revealed the increase of dietary lipid content linearly increased the serum total triglyceride (TG) content and aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. The expression of genes relating to lipid synthesis in the liver and muscle, including pparγ, fas, dgat1 and acc1 showed a significant quadratic trend with increasing dietary lipid level, and the highest expression was found in the group of L12.09. The liver lipolysis genes, including pparα, hsl and cpt1a showed a quadratic trend with increasing dietary lipid levels, and the lowest expression occurred in the group of L12.09. However, the expression of these genes in the muscle significantly decreased with increasing dietary lipid levels. Additionally, dietary lipid content linearly decreased muscle hardness, adhesiveness and shear force and linearly increased muscle gumminess of cultured fish. In conclusion, dietary lipid levels affected the growth performance, lipid metabolism and flesh texture of cultured mandarin fish and suitable dietary lipid level was 12-15 %.