Synergistic effects of Sargassum vulgare extract and lipid levels on growth performance, blood biochemical indices, immunological competence, and antioxidant capacity in juvenile common carp (Cyprinus carpio)

The aim of this study was to investigate the potential synergistic effects of Sargassum vulgare extract (SVe) and lipid (L) on growth, feed conversion, blood biochemistry, antioxidant protection, and immunity of juvenile carp (Cyprinus carp). Test diets were formulated with three levels of SVe (0, 7.5, and 15 g/kg) and two levels of lipids (50 and 100 g/kg): the control diets without additional SVe (SVe0L50; SVe0L100), 7.5 g SVe/kg (SVe7.5L50; SVe7.5L100), and 15 g SVe/kg (SVe15L50; SVe15L100). Three replicate fish tanks were randomly assigned to six experimental groups, each receiving one of the diets for a duration of eight weeks. The results showed that 7.5–15 g SVe/kg significantly improved growth performance and feed utilization. The SVe15L100 group showed improved health indicators, including higher concentrations of hematocrit, hemoglobin, high-density lipoprotein, total protein, globulin, lysozyme, and complement. Additionally, the SVe15L100 group displayed the most robust antioxidant capacity, as evidenced by higher serum levels of superoxide dismutase, glutathione peroxidase, catalase, and lower levels of malondialdehyde. Based on results, it is recommended to enrich the diet with 15 g SVe and 100 g lipid/kg for simultaneous enhancement of antioxidant capacity and immune of juvenile common carp.