In recent years, with the rapid development of China 's waterfowl breeding industry, the number of common infectious diseases in ducks has been increasing, resulting in a high level of morbidity and mortality of duck diseases, which has seriously affected the development of waterfowl industry and caused huge economic losses.In this experiment, the preparation and preliminary application of egg yolk antibody against duck-derived astrovirus were studied. In this study, PCR identification and phylogenetic tree analysis were used to inoculate duck embryos after gradient dilution of the virus solution, and the death rate was counted. The median lethal dose ( LD50 ) of duck embryos was calculated according to the Reed-Muench method. To propagate duck-derived astrovirus, duck embryos were utilized. The virus was then rendered inactive using formaldehyde and combined with Freund's adjuvant for immunizing white feather laying hens. Hyperimmune eggs were subsequently gathered, and IgY was extracted through a method of water dilution-ammonium sulfate. The prokaryotic expression pCold-TF vector of DASTV spike protein was constructed, and the recombinant plasmid was transformed into E.coli for expression, which achieved efficient soluble expression of spike protein. SDS-PAGE electrophoresis was used to identify the amount and concentration of antibody and antigen protein, and indirect ELISA was used to detect the antibody titer of IgY produced by immunized hens. In the animal protection experiment, Animal protective experiments and animal therapeutic experiments were carried out at the same time to verify the effect of egg yolk antibody.The results showed that the antigen could produce high titer egg yolk antibody. The titer of IgY detected by the indirect ELISA method established in this experiment was up to 1 : 1024. The virus titer was calculated to be 2 × 10²LD50 / ml by Reed-Muench. In the protective experiment, ducklings were subcutaneously injected with 0.2ml egg yolk antibody. When challenged with 10LD50 virus, the survival rate was 100 % after 15 days of challenge. When challenged with 20LD50 virus, the survival rate was 75 % after 15 days of challenge. In the therapeutic experiment, when the ducklings were challenged with 10LD50 virus and injected subcutaneously with 0.2mlIgY, the survival rate could reach 100 % after 15 days. When the ducklings were challenged with 20LD50 virus and injected subcutaneously with 0.2mlIgY, the survival rate could reach 75 % after 15 days.

Tianhao Yu, Xiaoyan Wu, Zhang Cao, Xu Zhang, Xinyuan Jiang, Jing Zhao, Yanlong Zhang. Preparation and Preliminary Application of Egg Yolk Antibody against Duck-derived Astrovirus. Academic Journal of Agriculture & Life Sciences (2024) Vol. 5 Issue 1: 22-29. https://doi.org/10.25236/AJALS.2024.050104.

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