1. College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
2. College of Life Science and Technology, Southwest Minzu University, Chengdu, China
3. Zhejiang Academy of Agricultural Sciences, Institute of Animal Husbandry and Veterinary Science, Hangzhou, China
4. College of Animal Science and Technology, China Agricultural University, Beijing, China
5. Research Center of Cattle and Sheep Embryo Engineering Technique of Hebei Province, Baoding, China