Dose-Dependent Effects of Dietary Tetrastigma hemsleyanum Supplementation on Growth Performance, Digestive Function, Antioxidant Capacity, and Immunity of Juvenile Leopard Coral Grouper (Plectropomus leopardus)

Tetrastigma hemsleyanum (TH) is a traditional Chinese medicinal herb with well-documented anti-inflammatory, antioxidant, and immunomodulatory properties, but its effects on aquatic animals remain unknown. To determine the effects of dietary TH supplementation, growth performance, digestive function, antioxidant capacity, and immune status were investigated in juvenile leopard coral grouper (Plectropomus leopardus). Five isonitrogenous and isolipidic experimental diets were formulated with TH tuber powder included at 0, 0.25%, 0.5%, 1%, and 2%. A total of 450 fish (initial body weight, 6.62 ± 0.16 g) were randomly allocated into five groups, with three replicate tanks per group. Each tank was stocked with 30 fish, and fish were fed the assigned diet for 8 weeks. Results showed that 0.25–0.5% TH significantly increased final body weight, weight gain rate, specific growth rate, and the specific activities of intestinal amylase, lipase, and trypsin without compromising feed conversion, whereas higher doses (1–2%) inhibited digestive enzyme activity and impaired feed utilization. In contrast, 1–2% TH markedly enhanced hepatic and serum antioxidant capacity, as indicated by elevated total antioxidant capacity and catalase, superoxide dismutase, and glutathione peroxidase activities, and reduced malondialdehyde content. Histological analysis revealed that high-dose TH improved intestinal villus morphology and appeared to ameliorate hepatocellular vacuolation. High-dose TH also upregulated intestinal tight junction and mucin genes (occludin, zo2, zo3, and mucin 2), downregulated hepatic pro-inflammatory cytokines (tnf-α, il-1β, il-6, il-8, ifn-γ), and upregulated anti-inflammatory il-10, accompanied by enhanced serum alkaline phosphatase, acid phosphatase, and lysozyme activities. In conclusion, low-dose (0.25%) TH promotes growth and feed efficiency, whereas high-dose (1–2%) TH enhanced antioxidant capacity, immune indices, and intestinal barrier function but impaired feed conversion, indicating that the inclusion level of TH should be carefully optimized according to production goals.