1. Laboratory of Animal Reproduction, College of Agriculture, Kinki University, Nara 631-8505, Japan.
2. Developmental Biology Department, National Institute of Agrobiological Sciences, Ibaraki, Japan.
3. Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Iwate, Japan.
4. Kumamoto Prefecture Livestock Stations and Animal Public Health Center, Kumamoto, Japan.