Effects of dietary immunostimulants on the growth and non-specific immune responses of hybrid sturgeons (Huso huso♀ × Acipenser ruthenus♂)

Herein, we investigated the effects of immunostimulants on the growth, immune responses, and post-infection survival of hybrid sturgeons (Huso huso♀ × Acipenser ruthenus♂). Therefore, we examined the effects of dietary supplementation of β-glucan, vitamin C, and Radix Bupleuri (Chaihu) extract (RBE) at various concentrations (0.2, 0.4, and 0.6% incorporated through feed) on the growth rate and non-specific immune responses of hybrid sturgeon. When supplemented individually, these immunostimulants significantly reduced the feed conversion ratio while promoting weight gain, with the vitamin C-administered groups showing the most pronounced differences. Further, we observed that dietary β-glucan, vitamin C, and RBE, when fed at 0.4 and 0.6% concentrations, significantly enhanced the rates of superoxide anion production and phagocytosis by head kidney leukocytes. Moreover, vitamin C and RBE supplementation at 0.4 and 0.6% and β-glucan supplementation at 0.6% concentration significantly increased the serum lysozyme activity. Further, vitamin C and β-glucan supplementation at 0.6% and RBE supplementation at 0.4 and 0.6% concentrations showed the highest survival rates after Aeromonas hydrophila infection. In conclusion, our findings highlight that the dietary supplementation of β-glucan, vitamin C, or RBE in appropriate concentrations can significantly enhance superoxide anion production and phagocytic activity of leukocytes, serum lysozyme activity, and the survival of hybrid sturgeons after A. hydrophila infection. Our results suggest that incorporating immunostimulants such as Chinese medicinal herbs at optimal levels can effectively boost the growth, immunity, and disease resistance of hybrid sturgeons in aquaculture. These results provide valuable insights for future studies on the inclusion of immunostimulants in aquaculture feed.