Why Does My Horse Have a Thin Sole?                

Horseback Magazine                             6-10-2013                                     Pete Ramey

In last month’s article, I discussed methods of estimating sole thickness. If you find that your horse has a thin sole, the next obvious question will be “why?”

Over-Trimming

First, be sure that no one is excessively trimming the sole. Sure, there is a time and place to remove or exfoliate excess sole tissue, but not on a horse with a thin sole—seems obvious, yet this is a very common problem. In domestic horses, the coffin bone often sinks to a lower-than-normal position within the hoof capsule over time. When this has occurred, the overall hoof capsule-length will seem “too long.” This leads many people to over-thin the sole in an attempt to make the hoof capsule-length seem more normal. It is possible to reverse this “sunken” condition, but meanwhile it is a serious mistake to shorten the hoof from the bottom so that the sole is less than 1/2 to 5/8 inches-thick.

This horse moves well, but has suffered from long-term “subclinical” laminitis from excess pasture and feed—the walls are flared and the sole is thin. Many practitioners were taught to always remove the layer of “dead” or exfoliating sole visible in the photo, leaving a clean, smooth post-trim finish. But since this horse has a thin sole—even with the crusty layer of dead sole present—it should not be “cleaned up,” as this would make the situation more dangerous for the horse. Photo reprinted from the book Care and Rehabilitation of the Equine Foot, P. Ramey.

General Nutrition

Most horses are (and should be) getting most of their nutrition from grass and hay. Nutrient levels in this forage vary, depending on many factors—region, season, growing conditions, etc. Horses living on free-choice grass and hay are usually getting inadequate levels of some nutrients, ideal levels of some nutrients, and an excess of some nutrients. To make up for this problem, horse owners tend to throw salt and mineral blocks out for the horses, provide daily feed concentrates, and perhaps additional mineral supplements. The tradition is perhaps “good enough” for most horses, but often leaves holes in the nutrition profile or dangerous excesses in some nutrients.

When the horse is “missing something,” the body wisely provides for the most important functions first—the ones that sustain life and fight disease. The skin gets the leftovers. This means that nutritional deficiency or imbalances can lead to thin soles (and most other problems with skin, coat and hooves).  So the first thing I do when I see these problems in client horses is start trying to more-scientifically balance the diet. This often means testing the forage and providing supplements that balance the individual horse’s nutrition profile.

Flared or “bell-shaped” walls, ripples in the wall, red stripes or spots in the wall—these are all possible signs of laminitis and should be taken seriously. These are much more than “cosmetic flaws.” Photo reprinted from the book Care and Rehabilitation of the Equine Foot, P. Ramey.

Past or Present Laminitis

When the laminae are compromised—usually because of excess sugars in the diet—the outer perimeter of the sole suffers from reduced blood flow. This can significantly slow down the growth of the sole. Additionally, the hoof walls in laminitic horses tend to separate from the bone, bending outward from their protective position around the sole. This loss of protection causes increased wear to the sole. The result of these two simultaneous factors: most laminitic horses, even mild cases, have dangerously thin soles.

If this condition is quickly reversed by veterinary intervention, competent farrier work and adequate changes to the diet, the horse can usually re-grow a perfect foot including a thick sole. However, if the situation is allowed to continue, over time, the coffin bone will remodel—losing mass around the outer perimeter and often developing a “ski-tip”-shape to the profile of the bone. Once this remodeling occurs, it is very common for horses to develop a permanent reduction of sole growth. This is just one more reason why “mild” laminitic symptoms—wall flare, rippled walls, shelly walls, red streaks, mild seasonal lameness—should never be ignored. An ounce of prevention is worth a ton of cure.

Insert Photo 4ramey3. Caption: This is a radiograph of a horse with long-term “sub-clinical” laminitis (this means that, for years, no one noticed except the horse). When the outer perimeter of the coffin bone loses mass and/or becomes wavy or fuzzy, it is common that the horse will have a difficult time growing a healthy sole—permanently. This is why it is so important to take action (dietary changes) when you first notice the slightest indicators of laminitis. Photo reprinted from the book Care and Rehabilitation of the Equine Foot, P. Ramey.

Environment

The ground the horse lives and works on has a significant effect on sole quality and thus thickness. If a horse lives in a soft, wet stall most of the time, the sole will be soft and weak. This is simple adaptation that would allow the sole to wear and exfoliate naturally under these conditions. If, however, this horse is suddenly thrust into a more abrasive environment and asked to perform, the sole can wear away too quickly. So it is best for the horse to, 1) dry up and add abrasion to the living environment, and 2) protect the soles (boots, shoes, etc.) during work and/or increases in activity or load.

It really helps the sole (and the horse’s feet in general) to vary the living terrain as much as possible. Add coarse gravel to high-traffic or muddy areas, add pea gravel to shady hangout spots, provide hard-packed areas, soft areas—just “mix it up” the best you can on your property. The resulting stimulation grows a better sole and packs it into dense callus.

Genetics

As I have discussed in previous articles, genetics are always a factor to some extent. But they are too often used as a scapegoat—they give people an excuse for not doing everything they can to optimize the situation. For instance, thoroughbreds may inherently tend to have a thinner sole than working-stock quarter horses, but fewer thoroughbreds have a chance to grow the very-best sole they could grow—their genetics are only one of many factors.  I have seen thoroughbreds raised outdoors in abrasive terrain, and they tend to grow very nice feet in these conditions—and the flip-side—I have seen nice working-stock quarter horses that were pampered indoors. Guess what their feet tend to look like?

In my experience, the most important genetic factor affecting sole thickness is the “thrifty gene.”  The most efficient “easy keeper” in the herd is most likely to be the one that gets laminitis, and thus the long- or short-term thin sole problems already discussed. But again, it is not the horse’s fault if he is fed more than he needs.

Hoof Protection

Whatever the cause of the thin soles, it is critical that you protect the thin-soled horse from bruising and excess abrasion during work, exercise and from hard or rocky terrain. Sole health is one of the reasons I like hoof boots so much. They allow barefoot turnout to optimize stimulation, growth and callusing of the sole, and then you can boot the horse for complete protection during work and trips to harsher terrain. But whatever you use—synthetic or traditional shoes, clogs, casts, epoxies—protecting thin soles is essential.  You should never expect a thin sole to do the job of protecting the sensitive internal structures of the foot. At the same time, though, don’t get so caught up in “protection” that you forget that you may be able to really fix the situation with simple changes to the horse’s care.