1. Laboratory of Theriogenology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
2. Laboratory of Clinical Veterinary Medicine for Large Animal, School of Veterinary Medicine, Kitasato University, Towada 034-8628, Japan
3. Laboratory of Theriogenology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
4. Laboratory of Animal Reproduction, Department of Animal Science, School of Veterinary Medicine, Kitasato University, Towada 034-8628, Japan