1. Laboratory of Animal Genetics; Department of Sustainable Agriculture; College of Agriculture, Food and Environment Sciences; Rakuno Gakuen University; Hokkaido 069-0836 Japan
2. Department of Agricultural and Environmental Biology; Graduate School of Agricultural and Life Sciences; The University of Tokyo; Tokyo 113-8657 Japan
3. Field Science Center for Northern Biosphere; Hokkaido University; Hokkaido 056-0141 Japan
4. Hokkaido Native Horse Preservation Association; Hokkaido 063-0804 Japan