Directional asymmetry of facial and limb traits in Equus Caballus and a comparison of horse and pony bilateral traits

Bilateral trait symmetry has been linked to superior athletic function; however positive performance in racing has recently been linked to directional asymmetry. Lack of comparative research prevents a better understanding of these findings. Direct measurements of 11 bilateral facial and limb traits were taken from 100 horses (mixed age, breed and gender). Directional asymmetry was calculated (DA = L-R). Results were reviewed as pooled data and horses (>148cm n=57) and ponies (≤148cm; n=43). Non-functional traits within pooled data all demonstrated PDA. Third metacarpal and third metatarsal were longer on the right and wider on the left with larger right limb joint dimensions. Pony DA only differed from horse and pooled data for lengths of non-functional traits. Results reflect previous racehorses finding, though this more representative population questions suggestions of asymmetries being either consequences of training stresses or results of selective breeding strategies and indicates a potential link with species genetics.