Grip and Slippage of the Horseʹs Hoof on Solid Substrates measured ex Vivo

A modified standard friction test was used ex vivo to investigate static and dynamic coefficients of friction image and image between horses hooves and five substrates. Mean values for image and image (± standard error of the mean, SEM) were: 0·477 (0·010) and 0·281 (0·009) for steel, 1·024 (0·028) and 0·821 (0·018) for patterned rubber, 0·998 (0·019) and 0·846 (0·013) for smooth rubber, 0·887 (0·015) and 0·710 (0·013) for concrete, and 1·043 (0·017) and 0·638 (0·017) for HL3 grade asphalt. All coefficients were independent of the normal contact force (probability image). Comparison with ratios of horizontal and vertical force components between the hoof and ground, recorded in vivo, suggests that slip occurs in the first 25 ms of contact. The results also indicate the extent to which ground contact constrains the natural expansion of the lower border of the hoof under load.