1. College of Life Sciences, Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong Qingdao Agricultural University Qingdao 266109 P. R. China
2. State Key Laboratory of Animal Nutrition, Institute of Animal Sciences Chinese Academy of Agricultural Sciences Beijing 100000 P. R. China
3. Fertility Preservation Lab and Guangdong‐Hong Kong Metabolism & Reproduction Joint Laboratory, Reproductive Medicine Center Guangdong Second Provincial General Hospital Guangzhou 510317 P. R. China
4. College of Horticulture Qingdao Agricultural University Qingdao 266109 P. R. China