1. Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, 1–1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657–8501, Japan
2. Department of Veterinary Laboratory Animal Science, Faculty of Agriculture, Tottori University, 4–101 Koyama-cho Minami, Tottori, Tottori 680–8553, Japan