1. Kyoto University, Sakyo, 606-8502 Kyoto, Japan.
2. NARO Institute of Livestock and Grassland Science, Tsukuba, 305-0901 Ibaraki, Japan.
3. National Livestock Breeding Center, Nishigo, 961-8511, Fukushima, Japan.
4. Tottori Prefectural Livestock Research Center, Kotoura 689-2503, Tottori, Japan.