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