1. Department of Large Animal Clinical Science, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido 069-8501, Japan
2. Department of Clinical Sciences, Faculty of Veterinary Medicine, Hokkaido University, Hokkaido 060-0818, Japan
3. Department of Environmental Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Hokkaido 060-0818, Japan