Variation in conformation in a cohort of National Hunt racehorses

REASONS FOR PERFORMING THE STUDY: Assessment of conformation is commonly used in the selection of horses for performance purposes. Little information is available on the normal range of conformational traits within the Thoroughbred population. OBJECTIVES: To describe variations in conformation in a cohort of racing Thoroughbreds in order to provide a set of baseline standards within which conformational traits can be considered normal. MATERIALS AND METHODS: Ninety-eight conformational parameters were measured in a cohort of 108 National Hunt racehorses using a digital motion analysis system. The measurements consisted of segment lengths, joint angles in 2D and 3D, inclinations, deviations and circumference measurements. The differences between left and right sides were determined to obtain a measure of asymmetry. Conformational parameters were related to each horse's country of origin, preferred race distance and race type. RESULTS: The majority of parameters followed a normal distribution with the biggest relative variation in hoof related measurements and in stifle and coxal angle. All circumference measurements and the majority of the length measurements were significantly correlated with the height of the horse at the withers. No underlying pattern of combinations of conformational parameters was identified. Twenty-five per cent of the parameters showed a significant difference between left and right-sided measurements. A significant difference in girth and intermandibular width was observed between Irish and French horses. CONCLUSIONS: Thoroughbreds differ from other breeds, not only with regard to segment lengths but also with regard to joint angles and deviations. Variation in conformational parameters was relatively small and no distinct pattern of combinations of conformational traits identified. CLINICAL RELEVANCE: The variation in conformational measurements in Thoroughbred racehorses establishes a set of baseline measurements of conformational range against which individual horses can be assessed.