Effects of dietary supplementation with fermented Astragalus membranaceus on growth performance, antioxidant capacity and intestinal barrier function of common carp (Cyprinus carpio)

The findings demonstrated that supplementation with fermented AM preparations significantly improved the final body weight, weight gain rate, specific growth rate, and feed protein efficiency of common carp, while markedly decreasing the feed conversion ratio (<i>p</i> < 0.05). Furthermore, there was a notable enhancement in serum antioxidant activity and immune responses, evidenced by increased levels of superoxide dismutase, catalase, glutathione peroxidase, lysozyme, and phagocytic activity (<i>p</i> < 0.05), alongside reduced levels of malondialdehyde (<i>p</i> < 0.05). The supplementation also improved intestinal health by enhancing intestinal barrier function, as indicated by the stimulation of the PI3K/AKT/mTOR signaling pathway, which led to increased expression of tight junction proteins (<i>p</i> < 0.05). Additionally, it promoted the formation of the intestinal mucus layer, increased the secretion of lysozyme and alkaline phosphatase (<i>p</i> < 0.05), activated the Nrf2 signaling pathway to upregulate antioxidant-related genes (<i>p</i> < 0.05), and inhibited the TLR4/MyD88/NF-κB signaling pathway, thereby reducing pro-inflammatory responses. These findings indicate that fermented AM preparations can improve the antioxidant potential and immune functions, thus promote the growth of common carp.