Effect of Dandelion Root Extract on Growth, Biochemical Indices, Antioxidant Capacity, Intestinal Histomorphology and Microbiota in Micropterus salmoides

Intensive aquaculture systems face challenges including compromised immune function and hepatointestinal damage in cultured species. Therefore, it is urgent to seek effective feed additives to strengthen health and immunity in intensive aquaculture. This study evaluated the potential of dandelion root extract (DRE) for improving growth performance, immune response, and hepatointestinal health in juvenile largemouth bass (Micropterus salmoides). Fish were fed diets supplemented with 0.05% (DRE1), 0.1% (DRE2), and 0.15% (DRE3) DRE for 42 days. The results showed that DRE supplementation had no significant effect on growth performance indicators (p > 0.05). However, compared to the control group, the DRE2 and DRE3 groups exhibited significantly reduced AST and ALT activities (p < 0.05). Lysozyme (LZM) activity increased significantly in all DRE groups, while alkaline phosphatase (AKP) activity was significantly elevated in the DRE2 and DRE3 groups (p < 0.05). In the liver, catalase (CAT) activity was significantly higher in the DRE2 group compared to the control (p < 0.05), and total antioxidant capacity (T-AOC) was significantly enhanced in DRE2 (p < 0.05). DRE also improved intestinal morphology, with significantly greater muscularis thickness in DRE2 and villus height in DRE3 compared to the control (p < 0.05). Also, serum D-lactate content was significantly decreased in all DRE-supplemented groups. Regarding intestinal microbiota, DRE2 supplementation resulted in an increased relative abundance of beneficial bacteria (Firmicutes) and a decreased relative abundance of potentially pathogenic bacteria (Proteobacteria), indicating favorable restructuring of the gut microbiota by DRE. In conclusion, dietary DRE supplementation, notably at 0.10%, enhanced antioxidant capacity and immunity while improving hepatointestinal health in largemouth bass, demonstrating potential as a functional feed additive in aquaculture.