THOMASON, JJ; MCCLINCHEY, HL; JOFRIET, JC; DICKEY, JP; RUNCIMAN, J; DOUGLAS, JE; Univ. of Guelph, Guelph; Univ. of Guelph, Guelph; Univ. of Guelph, Guelph; Univ. of Guelph, Guelph; Univ. of Guelph, Guelph; Equine Research Centre, Guelph: Anatomical construction of the horse’s hoof for weightbearing

The horse�s hoof is constructed to withstand the shock of rapid repeated contact with a semipredictable substrate, and to withstand forces which may peak at over 3x bodyweight. We present the results of several complementary experiments examining the hoof�s adaptations for transmitting forces between the ground and the skeleton, with some preliminary work on shock absorption. Data are collated from in vivo strain gauge recordings, quantitative morphometry, in vitro materials and structural testing, 3-D finite-element analyses and in vivo accelerometry. Force is transmitted through the hoof wall to the skeleton via a soft-tissue connection: the laminar junction. Regional variation in quantitative morphometry of this junction correlates with in vivo and FE predictions of local variability in loading. Load variability is dependent upon factors such as gait, direction of travel, substrate, and external hoof shape. The morphology of the junction also correlates with differences in hoof shape. We have constructed a hypothetical 3-way feedback mechanism among hoof shape, internal stress distribution and morphology of the laminar junction for examination in future work. Preliminary accelerometry experiments show transient (2-3ms) spikes reaching or exceeding 750g (>7000 m/s/s) at the hoof surface of unshod horses trotting at 5-7m/s, which we interpret as a shock wave traveling through the hoof wall. This shock is attenuated before it reaches the skeleton which strongly implicates the laminar junction as an important spring-damper mechanism.