1. Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan
2. Laboratory of Companion Animal Research, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
3. Faculty of Medical Sciences, University of Fukui, 23–3 Matsuoka-shimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910–1193, Japan
4. Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464–8601, Japan
5. Division of Animal Science, National Institute of Agrobiological Sciences, 2 Ikenodai, Tsukuba, Ibaraki 305–0901, Japan