1. Laboratory of Reproductive Physiology, Graduate School of Environmental and Life Sciences, Okayama University, Okayama 700-8530, Japan
2. Laboratory of Theriogenology, Joint Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, Tottori 680-8550, Japan
3. Obihiro University of Agriculture and Veterinary Medicine, Inada Nishi 2-11, Obihiro 080-8555, Japan