Quantifying the equine hoof's response to loading during exercise

The equine hoof changes in external shape and anatomical structures over time in response to a variety of internal and external stimuli. Variation in mechanical loading is one such stimulus, but evidence of its role is more based on empiricism rather than experiment. The first aim of this study was to document the changes over time in growth rate, strain distribution, external shape and internal anatomy of the equine hoof.; Eighteen mature Standardbred horses were selected; 9 horses were exercised regularly for four months, while the other 9 horses received no forced exercise. Shape and anatomy were quantified by a series of morphometric variables. Strain in the hoof wall was measured using rosette gauges at three circumferential positions (toe and both quarters of the wall). Those four parameters were measured before and after the experiment and the results were statistically compared between and within the groups. Changes in the morphometric variables (external and internal anatomy) were also assessed by examining the pattern of pairwise correlations among those variables.; Both groups showed some changes over time. Exercise caused some significant changes in strain distribution at the three positions. Exercise caused a decrease in principal and peak compressive strains at all the positions, while in the controls those variables increased at both quarters. Exercise also decreased variations in principal tensile, principal and peak compressive strains; quarters also showed significant changes in principal tensile strain. The differences between the groups were subtle in hoof wall growth, hoof shape and internal morphology. The number of pairwise correlations decreased among variables of the hoof shape and increased among the variables of internal anatomy due to exercise.; This work documented the changes in hoof shape over a 4 month period and provided evidence for changes in the biomechanics and morphology of the hoof in response to exercise.