1. Department of Reproduction, Nippon Veterinary and Life Science University
2. International Institute of Small Animal Medicine, Bio Plus, AHB Inc.
3. Department of Reproduction, Nippon Veterinary and Life Science University, 1–7–1 Kyonan-cho, Musashino-shi, Tokyo 180–8602, Japan
4. International Institute of Small Animal Medicine, Bio Plus, AHB Inc., 2–7–2 Sumiyoshi, Koutou-ku, Tokyo 135–0002, Japan