1. Wången National Center for Education in Trotting, Vången 110, S-835 93 Alsen, Sweden
2. Hästforsk, Sörsvedje 120, S-893 91 Bjästa, Sweden
3. Dept. of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Box 7011, S-750 07 Uppsala, Sweden