1. College of Veterinary Medicine, Shaanxi Centre of Stem Cell Engineering and Technology, Northwest A&F University, Yangling, Shaanxi, China.
2. Department of Pathology, Yangling Demonstration Zone Hospital, Yangling, Shaanxi, China.
3. Key Laboratory for Mammalian Reproductive Biology and Biotechnology, Ministry of Education, Inner Mongolia University, Hohhot, China.