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QUESTION: Is there anything I can do to get my horse to grow thicker soles?
DR. SCOTT MORRISON: This is probably the most common question I get asked. The answer is yes — in most cases. Are the soles thin in the toe region? Heel region? Or just thin in general? Club feet will have good sole depth in the heel and thin depth in the toe, where low heeled feet will be the opposite. Treatment of club feet and low heel feet are probably an entirely different topic requiring a different discussion.
Some breeds inherently have thinner soles in general. For example, hot-blooded horses, like Thoroughbreds, have thinner integument (skin, hoof wall and soles) to help dissipate heat and lighten their body mass to run more efficiently.
Also foot conformation can play a role in sole thickness. The arch of the sole or “cup” is dictated by the shape or conformation of the hoof. Horses with flat feet, or no cup and lower arch, typically have thin soles, whereas feet with a higher arch or are more “cuppy” generally have better sole depth.
The arch of the foot is dependent on the hoof wall shape or slope. Since the sole is connected to the wall, if the wall flares or slopes excessively, it will pull on the sole arch and flatten it. The mechanics of how a horse is trimmed and shod can significantly improve the arch and subsequently the sole depth. Using trimming and shoeing techniques to decrease flaring of the wall in the quarters will help “tighten up” the foot and improve the arch. Rolling the quarters of the hoof wall up from the ground surface will help decrease the horizontal pulling force on the wall and decrease this flaring. Care should be taken to only do this from the ground or sole surface; excessive filing of the outer hoof wall will make it thinner, weaker and more susceptible to flaring. Additionally these same mechanics can be implemented into a shoe. Rolling and doming a shoe in the quarters and toe will help decrease flaring and improve the arch.
For some reason shoes that facilitate break over tend to help the horse grow a thicker sole. For rehabilitation of thin soles, I often use a roller motion-style shoe in which there is a roll to the toe and a roll to the heel of the shoe. This takes stress off of the hoof and probably aids in perfusion to the sensitive sole, which in turn produces more sole tissue.
Another factor in the horse's collapsing arch is arch or sole support. If you look at the horse in its natural state, you will see the feet are often packed with dirt. This provides a natural arch support. Many of our well cared for domestic horses have their feet picked out at night and are put into a stall with shavings or straw which do not provide any support to the arch. These horses spend excessive amounts of time only bearing weight on the perimeter hoof wall with their arch suspended. Over time their arch will collapse and flatten out. This can be easily seen as the frog begins to prolapse or be closer to the ground than the ground surface of the hoof wall. This is a clear indication that the foot needs more arch support.
For this reason I find the use of artificial sole supports very useful in my practice for rehabilitating feet. Arch supports can be anything that provides support to the frog and or sole. Heart bars, silicone, urethane, and various elastomers are the most commonly used. Often some of these materials can be used beneath a pad. Some of these materials will adhere to the sole themselves (urethanes) and not require a pad to hold them in.
Every horse is a little bit different and some can be intolerant to one type of arch support and not another. Some of the products are softer than others. In my opinion every horse can tolerate some form of arch support. I have found even temporary orthotic sole supports beneficial. For example, a custom-made elastomer sole support can be made which is placed in the horse's foot when in the stall and removed when they get turned out or ridden. This technique provides the horse arch support during the majority of the day when they are in the stall. Temporary orthotics have the benefit of not being in the foot when the horse is competing or exercising. For example, sometimes you don't want the extra weight or decreased traction of an arch support when being ridden but still need the benefit of the support the other 20+ hours of the day.
Pads can also be beneficial — not only do they add an extra layer of protection, they also decrease the wearing away of the sole from the abrasive ground surface. I have used many different types of pads over the years and I have found that the foot tends to respond better to just leather pads, probably because it is natural and is similar in consistency and make up as the horse's sole. The leather pad can breathe, wick away moisture, and conforms and molds to the horse's foot over time.
Supplements which aid wall growth also aid sole growth since the wall and the sole are of similar make up. Biotin and fatty acids tend to improve the quality and growth rate of the wall and sole. Care should taken when using many supplements. It is easy to over-supplement, creating low level toxicities which may have the opposite effect than you are trying to achieve. Horses on well balanced diets should be supplemented with caution. However, Biotin and fatty acids are relatively safe to supplement with.
Topical chemicals to harden the sole are often promoted heavily to horse owners. They might help alleviate temporary soreness, however, be careful not to overuse caustic products. They may temporarily harden the sole but overtime denature proteins and damage the sole tissue and actually make it thinner. A general rule is: if you wouldn't apply to the skin anywhere else on the horse's body, then you probably shouldn't put it on the horse's foot.
In conclusion, we see that there are many ways to help thicken your horse's sole, but you should always work closely with your veterinarian and your farrier to achieve your goal. They are in the best position to make recommendations that take into consideration your particular horse's hoof mechanics.
Dr. Scott Morrison is both a veterinarian and a farrier, having graduated from both Virginia Maryland Regional College of Veterinary Medicine and the Eastern School of Farriery. He helped develop Rood and Riddle's Podiatry Center, now oversees the podiatry department and is a shareholder in the hospital.
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