ACKNOWLEDGEMENTS
This study was funded by grants from the State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (SKLVEB2016KFKT014), China Postdoctoral Science Foundation (2017M610659, 2018T111113), Science and Technology Department of Jiangxi Province (20194ABC28008), and the Fundamental Research Funds for the Central Universities (2452019053). The authors thank Dr. Chuang Lyu from Qingdao Jiazhi Biotechnology Co., Ltd. in Qingdao, Shandong province for proofreading the manuscript.