[1] Natl Inst Agrobiol Sci, Anim Genome Res Unit, Tsukuba, Ibaraki 3050901, Japan
[2] Univ Tsukuba, Grad Sch Comprehens Human Sci, Tsukuba, Ibaraki, Japan
[3] Natl Inst Anim Hlth, Tsukuba, Ibaraki 305, Japan
[4] Hirosaki Univ, Grad Sch Hlth Sci, Hirosaki, Aomori, Japan
[5] Utsunomiya Univ, Fac Agr, Utsunomiya, Tochigi 321, Japan
[6] United Grad Sch Agr Sci, Tokyo, Japan
[7] Univ Agr & Technol, Tokyo, Japan
[8] RIKEN, Bio Resource Ctr, Tsukuba, Ibaraki, Japan