Part of what makes veterinary medicine so interesting is that you get to learn a little bit about everything. For instance, while learning about common equine diseases, we’ve picked up bits and pieces about farriery, nutrition, and equine sports.
A few days ago our topic at educational rounds was horseshoes. The attending clinician brought a selection of shoes in plastic baggies, and as he passed them around, asked questions to gauge our knowledge and help fill in any gaps. Using our knowledge of anatomy, physics, and common diseases, we worked as a group to logically figure out why each horseshoe looked the way it did. For example, one shoe had thicker heels, a beveled toe, and was made of aluminum. Aluminum is a lighter metal than iron, which helps compensate for the increased weight of thicker heels. Aluminum is also softer, though, so it has to be replaced more often. Thicker heels on the shoe help support the heel bulbs of the horse, decreasing the tension on the deep digital flexor (DDF) tendon as it stretches to attach to the coffin bone. The beveled toe decreases breakover effort, which describes the process of the heel lifting and the toe rotating as the hoof pushes off. If the toe of the shoe is beveled, it allows the toe to rotate prior to the heel lifting off the ground, which greatly decreases the amount of tension on the DDF tendon and navicular ligaments.
We also talked about the function of clips, which are semicircular extensions of the shoe that lie flush against the hoof walls. Clips increase the amount of surface area holding the horseshoe onto the hoof, which in turn helps resist the twisting and shearing forces when the horseshoe digs into the ground as the horse moves. Just as every horse need not be shod, not every shod horse needs shoes with clips—it’s very dependent on the individual horse and their workload.