Comparison of Gait Characteristics of Horses and the Effect of Farriery and Shoes

Abstract

Many equine athletes wear metal shoes to provide protection, support, and traction. The two most common horseshoe materials are steel and aluminum. In some equine disciplines, shoes are removed (barefoot) or changed to a lighter shoe material (aluminum) during an equestrian event to achieve perceived advantages such as more aesthetic limb flight. Shoeing has an impact on performance and health of athletic horses. Thus, the impact of shoe characteristics on performance and welfare of sport horses is coming under increased scrutiny. However, objective information regarding the effects of shoeing on gait characteristics of performance and show horses is scant and there is little scientific evidence to guide decisions about shoeing and its impact on competition fairness and animal welfare. Commonly utilized body-mounted inertial sensor systems can be used to measure symmetry of head and pelvic movement, but do not directly evaluate other gait characteristics important to subjective judging. More recently, triaxial hoof-mounted inertial sensor systems have been used to measure stride characteristics in horses. These sensors yield information about hoof orientation in all three axes and allow more detailed analysis compared to other systems. This technology could be a useful tool to measure changes in gaits of horses under various hoof shoeing conditions and yield information to help guide welfare policy. The objective of our study was to determine differences in gait characteristics pertinent to subjective judging of horses at the trot under various hoof shoeing conditions (barefoot, aluminum shoes, and steel shoes). We hypothesized that hoof shoeing conditions would not affect symmetry of head and pelvic movements as detected with body-mounted inertial sensors or mediolateral hoof deviation during swing phase, stride length, and duration of stride phases detected with hoof-mounted IMUs. We also hypothesized that lower foot-shoe weight (barefoot or aluminum shoes) would result in lower early and late swing phase hoof flight height (arc height a and arc height b, respectively) as detected with hoof-mounted IMUs. A prospective crossover design was used.

Twelve healthy, adult, client-owned horses without lameness, hoof or limb abnormalities, or positive response to hoof testers were included. The horses included multiple breeds (Quarter Horse, Thoroughbred, Warmblood, and mixed breed) and were used for several different disciplines (western, eventing, and pleasure riding). Horses were evaluated with body- and hoof- mounted inertial sensors at a trot on firm (asphalt) and soft (sand) surfaces. Evaluations were performed in the following order: with existing shoes (baseline), no shoes (barefoot), aluminum shoes and steel shoes. Hoof balance radiographs (lateromedial and dorsopalmar) were obtained at baseline, barefoot, and after each shoe change prior to data collection. All trimming and shoeing were performed by the same Certified Journeyman Farrier. Data were collected using body-mounted inertial sensors (Lameness Locator, Equinosis, Columbia, MO) and hoof-mounted triaxial inertial sensors (Hoofbeats, Werkman Black Tolbert Tolbert, Netherlands). Data collected included Q score (measure of head and pelvic asymmetry), hoof arc height and lateral deviation, stride length, and mid-stance, breakover, swing, and landing stride phase times. Data were compared among shoeing conditions and surfaces (asphalt and soft footing) and analyzed for statistical relevance. Normally distributed data was analyzed using a mixed model ANOVA. Skewed variables were analyzed using the least squares means and Tukey-Kramer to adjust for multiple comparisons. Significance was set as P < 0.05. Significant differences in arc height between aluminum and steel shoes were detected. Aluminum arc height was significantly smaller in both right and left forelimbs (P < 0.0001) in soft (P < 0.0001) and hard (P = 0.0009) footing compared to steel shoes. Barefoot arc height was significantly smaller on soft footing in both right (P = 0.0297) and left (P = 0.0006) forelimbs compared to steel shoes. Hoof arc height was not significantly different between barefoot conditions and aluminum shoes. No significant differences in Q score, lateral deviation, stride length, and mid-stance, breakover, swing, and landing stride phase times were observed. Limitations of the study included the small sample size, and the variation in horse use and breed. Future research should focus on horses of a single breed and those that are actively competing at high level hunters where the practice of changing shoeing conditions for perceived benefit is more relevant.

The null hypothesis that there is no correlation between shoeing conditions and hoof arc can be rejected; there are significant differences in the foot arc height for horses shod with aluminum shoes compared to steel shoes, and horses shod with steel shoes in comparison to barefoot conditions. Aluminum shoes did not change foot arc height compared with barefoot conditions and thus do not support the practice of removing aluminum shoes to compete barefoot in certain phases of competition as no significant differences in gait characteristics were observed. The significant findings of this study suggest further investigation is warranted to determine the impact this has on competition fairness and animal welfare.