“…Heritability estimates of speed vary from low to moderate (Villela et al, 2002;Ekiz et al, 2005b). Sex and age of a horse, trainer, track condition, racing distance, number of horses participating in a race, weather condition, carried weight, position in starting gates, and competition have been suggested as possible environmental factors affecting speed (Harkins et al, 1992;Oki et al, 1994;Mota et al, 1998). However, most studies investigated Thoroughbred horses (Oki et al, 1994;Martin et al, 1996;Ekiz et al, 2005b;Mota et al, 2005), whereas few studies identified environmental factors affecting speed of Arabian horses (Ekiz and Koçak, 2005;Ekiz et al, 2005a).…”