1. Department of Animal Science, School of Veterinary Medicine, Kitasato University, Aomori 034-8628, Japan
2. National Institute of Animal Health (NIAH), National Agriculture and Food Research Organization (NARO), Hokkaido 062-0045, Japan
3. Department of Sustainable Agriculture, College of Agriculture, Food and Environment Sciences, Rakuno Gakuen University, Hokkaido 069-8501, Japan