1. Equine Science Division; Hidaka Training and Research Center; Japan Racing Association; 535-13 Aza-Nishicha, Urakawa-cho, Urakawa-gun Hokkaido 057-0171 Japan
2. Department of Comparative Pathophysiology; Graduate School of Agricultural and Life Sciences; University of Tokyo; 1-1-1 Yayoi, Bunkyo-ku Tokyo 1 13-8657 Japan