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

Thisstudy explored the impact of immunostimulants on the growth, immune responses, and post-infection survival of hybrid sturgeon ( Huso huso ♀ × Acipenser ruthenus ♂). We examined the effects of β -glucan, vitamin C, and Radix Bupleuri (Chaihu) extract (RBE) at various concentrations (0.2%, 0.4%, and 0.6% feed) on the growth rate and non-specific immune responses of hybrid sturgeon. When added individually, these immunostimulants significantly reduced the feed conversion ratio while increasing weight gain, with the vitamin C groups showing the most pronounced differences. Immunity experiments demonstrated that 0.4% and 0.6% dietary β -glucan, vitamin C, and RBE significantly enhanced the superoxide anion production rate and phagocytic rate of head kidney leukocytes. The 0.4% and 0.6% vitamin C and RBE groups, along with the 0.6% β -glucan group, exhibited a significant increase in lysozyme activity. Moreover, the 0.6% vitamin C and β -glucan groups, as well as the 0.4% and 0.6% RBE groups, showed the highest survival rates after Aeromonas hydrophila infection. In conclusion, our findings highlight that appropriate dietary concentrations of β -glucan, vitamin C, or RBE significantly enhance superoxide anion production, phagocytic activity, serum lysozyme activity, and post- A. hydrophila infection survival in hybrid sturgeon. The results of this study suggest that incorporating immunostimulants, such as Chinese medicinal herbs, at optimal levels can effectively boost the growth, immunity, and disease resistance of hybrid sturgeon in aquaculture. These results provide valuable insights for future research on the inclusion of immunostimulants in aquaculture feeds.