Wednesday, March 18, 2009

One Step at a Time: Hoof Trimming and Leg Stress

by: Chad Mendell, Managing Editor

Have you ever walked in shoes that you've had forever that are just a little worn to one side of the heel or the other? Did you notice that after awhile your knees would start to hurt, or maybe your ankles? Now think about wearing those shoes 24 hours a day, every day, for an entire month without ever taking them off. Image how miserable you'd feel.

Now, apply that to the horse whose owner says he can go a few more weeks before he needs a trim or even worse, to a horse whose owner thinks the animal can go all winter without any hoof care. Now, take a step back and imagine wearing those ill- fitting shoes for the entire winter. You should cringe at the thought.

The reality is that horses' feet are often neglected, especially during the winter months. Shoes are usually pulled, farrier visits become less frequent, and the horses are left to suffer.

As a rule of thumb, we know that our horses should be trimmed (and shod if necessary) at least every six to eight weeks. But where did those numbers come from? Sure, after eight weeks, hooves will start to appear long, they might crack or chip and look unsightly, or on a horse with poor conformation, the feet might show uneven wear. All of these observations might seem benign on the surface, but they're important, according to Meike van Heel, MSc, BSc, PhD, a researcher at Utrecht University's Equine Performance Laboratory in the Netherlands. Van Heel recently studied how a hoof changes between trims, and she found that neglecting your horse's feet could be setting him up for serious injury.

Van Heel says most early retirements in equestrian sports are the result of lameness problems caused by overloading injuries. Such injuries occur when the amount of force placed on a soft tissue structure (such as the tendon) exceeds its loading capacity. Severe overloading can cause an immediate effect resulting in acute damage. However, most overloading is chronic and repetitive, and it results in the injury of lesion-prone tissues of the limb, primarily tendons, ligaments, and articular cartilage.

In a series of recent studies, van Heel and a group of Utrecht researchers closely observed and measured the changes that occurred in horses' hooves during an eight-week shoeing interval. With the help of radiographs, motion sensors, video recordings, and pressure plate systems designed by van Heel, researchers were able to observe two major changes in the hooves that occurred during those eight weeks: The breakover point (the phase of stride between the time the horse's heel lifts off the ground and the time the toe is lifted) moved back toward the heel, and the hoof angle (the angle of the front of the hoof wall with the ground, as viewed from the side) significantly decreased, both of which, van Heel says, can place added stress to lesion-prone tissues in the leg.


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