Effects of dietary lipid levels on growth performance, hepatic health, lipid metabolism and intestinal microbiota on Trachinotus ovatus

Proper dietary lipid is beneficial for the protein-sparing effect and reduces feed budget. Therefore, 8 weeks trial feeding with different lipid levels diets was performed to determine the optimal supplement level through the investigation on growth performance, hepatic health, lipid metabolism and intestinal microbiota of Trachinotus ovatus. Six diets (D1 - D6) containing 90 g/kg, 120 g/kg, 150 g/kg, 180 g/kg, 210 g/kg and 240 g/kg lipid were formulated, respectively. Each diet was randomly assigned to four groups of fish (initial body weight 7.58 +/- 0.10 g), and fish was fed twice daily to apparent satiation. Results showed that the weight gain and the specific growth rate of T. ovatus fed with D2 diet were significantly higher than the D1, D5 and D6 treatments (p < .05), and D2 treatment did not show a statistical difference with D3 and D4 treatments. Related antioxidant enzyme activities such as superoxide dismutase, as well as the RNA expression of antioxidant genes, such as glutathione reductase, showing a significant upward and then downward trend with the increase of dietary lipid, and D4 treatments reached the highest value. One of the intestinal microbiotas-Nocardiaceae, demonstrating a similar change trend to the antioxidant capacity of fish. Transaminase of serum and malondialdehyde of liver in D5 and D6 treatments significantly higher than D1 treatments (p < .05). Hepatic RNA expression of PPAR alpha and CPT-I increased first and then decreased with the increase of lipid level, obtaining the highest value in D4 and D5 treatments respectively. In conclusion, dietary lipid from 120 g/kg to 180 kg/kg is beneficial for growth and health of T. ovatus.