1. Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, Shandong, China;
2. Shandong Key Laboratory of Animal Disease control and Breeding, Jinan, Shandong, China;
3. Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, China;
4. College of Life Sciences, Shandong Normal University, Jinan, Shandong, China