1. United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi 753-8515, Japan
2. Fukuoka Prefecture Dairy Cooperative Association, Fukuoka 819-0373, Japan
3. Department of Animal Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
4. Department of Farm Animal Health, Utrecht University, Yalelaan 7, 3584 CL Utrecht, the Netherlands
5. Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi 753-8515, Japan