1. Key Laboratory of Animal Biotechnology of the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Xianyang 712100, China
2. Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Xianyang 712100, China
3. Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Xianyang 712100, China