Changes in growth of the hoof wall and hoof morphology in response to regular periods of trotting exercise in Standardbreds.

OBJECTIVE: To quantitate changes in hoof wall growth and hoof morphology induced by mild exercise in Standardbreds. ANIMALS: 18 Standardbreds. PROCEDURES: Horses were exercised at approximately 6 m/s (4,200 to 5,600 m/d) on 4 d/wk for 17 weeks. Both exercise (n = 9) and nonexercise (control group; 9) groups were housed in a large paddock throughout the study. At the beginning and end of the study, right forelimb feet of all horses were digitally photographed and underwent magnetic resonance imaging. Hoof wall measurements were obtained from the images to evaluate hoof wall growth and morphometric variables. Data were compared between the groups and within each group via a quadratic model. Changes in each variable and pairwise correlations between variables were evaluated.
RESULTS: Morphometric variables did not significantly differ between the control and exercise groups. However, differences within each group between the start and the end of the study were significant for several variables; overall, values for hoof wall variables increased and those for solar variables decreased. Between the beginning and the end of the study, the amount of variation in values of hoof capsule variables in the exercise group decreased to a greater extent, compared with control group findings. Patterns of pairwise correlations for variables differed between the groups. CONCLUSIONS AND CLINICAL RELEVANCE: In Standardbreds, mild exercise for 17 weeks caused no significant changes in hoof wall growth or morphometric variables. Subtle changes may develop in equine hooves in response to loading, and mild exercise may not be a strong adaptive stimulus.