1. Animal Breeding and Reproduction Research Division, NARO Institute of Livestock and Grassland Science, Ibaraki 305-0901, Japan
2. Present: National Livestock Breeding Center Tokachi Station, Hokkaido 080-0572, Japan
3. Miyagi Prefecture Tobu Livestock Hygiene Service Center, Miyagi 987-0811, Japan
4. Present: Division of Animal Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba 305-0901, Japan
5. Food and Fertilizer Technology Center, Taipei 10648, Taiwan
6. Present: Department of Research Planning and Coordination Headquarters, National Agriculture and Food Research Organization (NARO), Ibaraki 305-0901, Japan