1. Department of Veterinary Pathology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan
2. The Japan Bloodhorse Breeders' Association, Shinbashi 4-5-4, Minato-ku, Tokyo 105-0004, Japan
3. Department of Theriogenology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada-shi, Aomori 034-8628, Japan