[Background] The widespread presence of Riemerella anatipestifer in poultry farms causes contagious serositis in ducklings, which seriously endangers the development of the poultry industry.[Objective] To improve the fermentation level and antigenic activity of R. anatipestifer and provide technical guidance for the development of R. anatipestifer inactivated vaccines. [Methods] The single factor test and response surface methodology were employed to optimize the vaccine medium for R. anatipestifer. The antigenic activity of R. anatipestifer was determined at different time points of fermentation, and the inactivated vaccine was prepared at the time point with the highest antigenic activity. The immune effect of the vaccine was evaluated by animal immunization test. [Results] The viable cell count of R. anatipestifer in the developed vaccine medium reached 4.68×1010 CFU/mL, which was 2.29 times higher than that of the commercial medium for R. anatipestifer. The antigenic activity of the strain peaked after 12 h of fermentation. The inactivated vaccine prepared at this time point induced significantly higher antibody level in mice than the commercial inactivated vaccines, with 100% protection from virus attack. [Conclusion] The medium developed in this study had excellent enrichment effect and can be used for the production of antigens for R. anatipestifer inactivated vaccine. The bacteria can be collected when the antigenic activity of the selected strain reaches the highest level during the vaccine production.
