1. State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, P. R. China
2. Key Laboratory of Preventive Veterinary Medicine in Hubei Province, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, P. R. China
3. The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan 430070, P. R. China
4. College of Science, Huazhong Agricultural University, Wuhan 430070, P. R. China