ACKNOWLEDGMENTS
This study was funded by grants from Xi’an IRIS Livestock Technology Co. Ltd. (K4030218170), China Postdoctoral Science Foundation (2017M610659, 2018T111113), the State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (SKLVEB2016KFKT014) and the Fundamental Research Funds for the Central Universities (2452019053). The authors thank Ass. Prof. Tomasz Stenzel from Department of Bird Diseases, Faculty of Veterinary Medicine in Olsztyn for proofreading the manuscript.