Dietary Puerarin Enhances Growth, Immune Function, Antioxidant Capacity, and Disease Resistance in Farmed Largemouth Bass, Micropterus salmoides

Puerarin, a bioactive isoflavone extracted from Pueraria lobata, possesses well-documented pharmacological properties, including anti-inflammatory, antioxidant, and metabolic regulatory effects, which have been extensively studied in mammalian models and traditional medicine. Recently, its potential as a functional feed additive in aquaculture has garnered increasing attention. This study aimed to evaluate the effects of dietary puerarin supplementation on growth performance, immune response, antioxidant capacity, and disease resistance in largemouth bass, Micropterus salmoides. A total of 120 fish were randomly assigned to 4 dietary groups, receiving a basal diet supplemented with 0 (control), 200, 500, and 1000 mg/kg puerarin for 8 weeks. The results showed that dietary puerarin significantly (p < 0.05) improved weight gain, with the 200 mg/kg and 500 mg/kg groups exhibiting the best performance. Puerarin supplementation enhanced acid phosphatase (ACP), alkaline phosphatase (AKP), and lysozyme (LZM) activities, reduced malondialdehyde (MDA) levels, and increased superoxide dismutase (SOD) and catalase (CAT) activities, indicating improved immune function and oxidative stress resistance in groups receiving medium concentrations of puerarin supplementation. The expression of the TNF-α, IL-6, IL-8, and HSP70 genes was significantly downregulated, especially in the 200 mg/kg and 500 mg/kg groups, suggesting anti-inflammatory and anti-stress effects, while Nrf2 expression was upregulated in the 1000 mg/kg group, reinforcing its antioxidative role. Additionally, puerarin-fed fish exhibited significantly lower mortality rates following Aeromonas hydrophila infection, highlighting enhanced disease resistance. In summary, the dose-dependent effect of puerarin on largemouth bass aquaculture has been revealed in this study. Dietary supplementation with moderate doses of puerarin (200 and 500 mg/kg) effectively suppressed inflammation and enhanced immune function, while the highest dose (1000 mg/kg) may mildly activate the immune system. These findings suggest that puerarin is a promising phytogenic feed additive for improving fish health and aquaculture sustainability.