1. United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi 753-8515, Japan
2. Research Institute of Animal Husbandry, Zaisan-210153, Ulaanbaatar, Mongolia
3. Faculty of Agriculture, Kagoshima University, Kagoshima 890-0065, Japan
4. Faculty of Veterinary Medicine, Utrecht University, Yalelaan 104, The Netherlands