Optimal dietary lipid levels modulate lipid metabolism and gut microbiota to enhance growth and health in juvenile hybrid snakehead (Channa maculata ♀ × Channa argus ♂)

This study was designed to investigate the effects of dietary lipid levels on growth performance, antioxidant capacity, lipid metabolism and intestinal microbiota in juvenile hybrid snakehead ( Channa maculata ♀ × Channa argus ♂). Five experimental diets with varying lipid contents (5.73%, 7.94%, 10.46%, 13.23%, and 15.13%, designated as DL6, DL8, DL10, DL12, and DL14, respectively) were formulated to contain equivalent levels of protein for the study. Six hundred hybrid snakeheads were selected for a 6-week feeding trial with an initial weight of (12.08 ± 0.91) g and were randomly divided into 5 groups. The results showed that weight gain (WG) and feed conversion ratio (FCR) improved significantly with increasing dietary lipid levels up to 10.46%, after which the improvements plateaued. Fish fed diets containing 10.46% lipid showed significantly higher liver activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). Conversely, hepatic malondialdehyde (MDA) levels increased as dietary lipid content rose. The expression of stearoyl-CoA desaturase ( scd ), fatty acid synthase ( fas ), and lipoprotein lipase ( lpl ) decreased significantly with increasing dietary lipid levels, while the expression of peroxisome proliferator-activated receptor α ( pparα ) and fatty acid binding protein 1 ( fabp1 ) initially decreased and then increased significantly. Additionally, the expression of acetyl-CoA carboxylase ( acc ) and sterol regulatory element-binding protein 1 ( srebp1 ) first increased and then significantly decreased. The 16S rRNA analysis revealed that Actinobacteriota was the dominant bacterial phylum in the gut microbiota of the hybrid snakehead, and its abundance decreased significantly with increasing dietary lipid levels. Dietzia , Aeromicrobium , Nitriliruptor , Nesterenkonia , Ornithinimicrobium , and Bacillus are the main probiotic bacterial genera in the gut microbiota, which play key roles in antioxidant defense and the regulation of lipid metabolism. In conclusion, regression analysis indicated that the optimal growth performance and feed efficiency in hybrid snakehead were achieved with a dietary lipid level ranging between 10.0% and 10.2%.