1. Laboratory of Theriogenology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
2. Research Fellow of Japan Society for the Promotion of Science
3. Department of Theriogenology, Faculty of Veterinary Medicine, Assuit University, Assuit 71515, Egypt
4. Laboratory of Theriogenology, Department of Clinical Sciences, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan