The effect of an acute hoof wall angulation on the stride kinematics of trotting horses.

High speed cinematography was used to describe the stride kinematics in a group of six, sound horses subjected to two farriery treatments, designated 'normal' and 'acute' hoof angulation. Normal was defined as having the dorsal hoof wall aligned with the pastern axis, whereas the acute hoof angulation was approximately 10 degrees lower than the normal angle for the individual horse. The acute angle was achieved by allowing the toes to grow relatively longer than the heels. The results of a multivariate analysis of variance showed significant differences between the two farriery treatments in the mode of hoof impact with the ground and the duration of breakover. The acute angulation was associated with fewer heel-first impacts and a greater number of toe-first impacts than the normal angulation (P < 0.01). Breakover time was prolonged with the acute angulation (P < 0.01). There were no significant differences between the two farriery treatments in stride length, duration of the suspension phase of the stride or duration of the stance phases of the fore or hind limbs (P > 0.05). The fight arc of the toe was similar for the normal and acute hoof angles, reaching its highest point shortly after lift off, after which the toe followed a low fight path. There was an elevation of the toe in preparation for heel-first or flat-foot impact, but when impact was toe-first the trace approached the ground smoothly at a more acute angle.