1. Laboratory of Theriogenology, Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Iwate 020-8550, Japan
2. Present address: NOSAI Hidaka, Hokkaido 056-0016, Japan
3. Present address: Laboratory of Theriogenology, Department of Veterinary Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan
4. NOSAI Iwate Tonanbu, Iwate 028-0542, Japan
5. Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan