1. Veterinary Teaching Hospital, Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine Hokkaido University, Kita 19 Nishi 11, Kita‐ku Sapporo Hokkaido 060‐0819 Japan
2. Laboratory of Veterinary Advanced Medicine, Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine Hokkaido University, Kita 19 Nishi 11, Kita‐ku Sapporo Hokkaido 060‐0819 Japan
3. Laboratory of Veterinary Surgery, Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine Hokkaido University, Kita 19 Nishi 11, Kita‐ku Sapporo Hokkaido 060‐0819 Japan