1. School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan
2. National Agricultural Research Center for Hokkaido Region, National Agriculture and Food Research Organization, Sapporo, Hokkaido 062-8555, Japan
3. Faculty of Education, Art, and Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata-shi, Yamagata 990-8560, Japan