1. 1College of Animal Science and Technology, Northwest A&F University, Yangling, China
2. 2Shaanxi Provincial Key Laboratory of Animal Genetics, Breeding and Reproduction, Northwest A&F University, Yangling, China
3. 4Shaanxi Stem Cell Engineering Research Center, Northwest A&F University, Yangling, China
4. 3College of Forestry, Northwest A&F University, Yangling, China