A field guide to hoof cracks

When a defect appears in the wall of a horse’s hoof, it’s important to be able to distinguish a cosmetic flaw from a serious problem.
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First the good news: The vast majority of the time, those cracks, chips and dings you find on your horse’s hoof walls will be harmless blemishes.

MAR17Hoofcracks

Then there’s the bad news: On rare occasions, a hoof crack may be a serious problem that leads to unsoundness. Or a persistent crack may be a sign of chronic trouble. In a worst-case scenario, a deep crack may provide an entryway for potentially life-threatening infections inside the foot.

The key, of course, is to be able to distinguish the difference. 

“Many of the cracks that we see out on the farm, probably at least 90 percent, are not going to cause lameness,” says Dean Moshier, a farrier in Delaware, Ohio, whose clients include pleasure horses as well as top-level athletes. “Most are just superficial cracks, where the surface of the hoof wall looks rough and layered like shingles on a roof.”

Still, it’s a good idea to keep an eye on hoof cracks. Some that are minor to start with may worsen, and if your horse’s hoof cracks seem to be chronic, it’s a good idea to figure out why and take steps to prevent them. Here’s what you need to know.

Causes of hoof cracks

Hooves generally crack under pressure from some sort of trauma. The forces contributing to the crack can originate within the hoof---if there are balance problems from poor or neglected farriery work, for example, or conformation issues that place unusual strains on the hoof wall. And, of course, cracks can be caused by external traumas---any single serious blow to the hoof can cause injury, and cracks may also develop due to repeated concussion, such as the horse who gallops on unforgiving footing or who stomps at flies incessantly on hard ground.

Genetics also plays a role in the strength and thickness of a horse’s hoof walls---some horses are simply more prone to cracks than others. “A strong foot can withstand or overcome a lot of adverse factors, but a weaker foot may not be able to handle it,” says Steve Norman, a farrier from Georgetown, Kentucky. “Some horses just have more structural integrity in the feet, and certain breeds have stronger feet than others.”

Finally, one type of hoof wall defect---horizontal cracks that run parallel to the ground---is almost always caused by an abscess that drained through the coronary band and temporarily disrupted the formation of horn, creating a gap. Horizontal hoof cracks generally are not serious and will grow out without causing problems. “Horizontal cracks are usually the result of an injury or a gravel abscess that blew out at the coronary band,” says Moshier.

“Horizontal cracks are not normally lameness related, even though the initial cause of that crack could have been a lameness-causing abscess or foot injury,” he adds. “The crack itself is nothing to worry about. It will eventually grow out.” 

As the horizontal hoof crack nears the ground, your farrier may take steps to stabilize the “loose” piece so it does not break off prematurely. “Sometimes at that point I take out the unattached wall below the crack,” says Moshier.

The most common hoof cracks

You’ll hear many terms for hoof cracks---sand cracks, weather cracks, grass cracks, etc.---but the most basic way to describe these defects is according to their location and direction. These indicators also offer clues to the origin and severity of the problem.

Vertical cracks, which run perpendicular to the ground, are the most common. The reason has to do with the anatomy of the hoof wall itself. Like human fingernails, hoof wall is composed mainly of a protein called keratin, which forms tubules---structures that look like densely packed drinking straws. These tubules run vertically down the hoof, from the coronary band to the ground, and give the hoof much of its structural strength, like the rebar in concrete. Weaknesses that allow cracks to form are much more likely to develop between the parallel tubules than across them.

Location determines how serious these cracks are likely to be. Those that originate at the bottom edge of the hoof wall and climb upward are typically just a cosmetic concern that is likely to be eliminated at the next trimming. Vertical cracks that originate at the coronary band and grow downward are more worrisome, especially if they’re deep, because disruption at the coronary band affects the production of new, healthy horn. 

Vertical cracks are further defined by where they appear on the hoof wall:

• Toe cracks occur in the front third of the hoof. Because the hoof wall is thickest and strongest at the front of the hoof, serious cracks at the toe are less likely to be caused by external injuries. However, abscesses, bruises and other internal issues that loosen the bond between the hoof wall and the underlying connective tissues can create weakness in the structure that may result in a deep crack.

Chronic toe cracks can also occur in horses with conformation issues that increase stresses on the front of the hoof. “Abnormally high or low coffin bone angles cause toe cracks,” says Steve Kraus, BS, CJF, head farrier of the Cornell University College of Veterinary Medicine. “Often, long pasterns and low-angled heels cause the front of the hoof to extend too far ahead of the leg.” As the horse walks, the breakover places extreme leverage on the inside of the hoof wall, which can bend the wall inward and cause cracks.

“When a hoof has an abnormally high coffin bone angle, the hoof will land toe first, which also puts excessive force on the inner hoof wall, creating the crack,” says Kraus.

• Quarter cracks develop along the side of the hoof; these tend to cause more trouble than toe cracks because the wall is thinner and must flex as the hoof bears weight. Any cracks in the side of the hoof will be less stable and are more likely to lead to lameness. 

Quarter cracks are often caused by conformation defects in the legs, such as legs that toe out. “When the hoof is out of balance it creates too much pressure on one side of the capsule,” says Tommy Boudreau, a farrier in Mineral Wells, Texas. “This will push into the coronary band and cause it to jam up. With all the extra pressure in one spot on that side of the foot it can make it break out and crack.”

These conformation faults tend to create chronic cracks in a predicable location, says Kraus: “If you drop a plumb line down from the front of the horse’s shoulder, it will point to the crack.”

An underrun heel and long toe also places stresses on the quarters with each step. The prying forces will separate the hoof wall at the bottom first, and the crack will grow upward. Its edges will spread apart as the horse bears weight. 

• Heel cracks occur at the rear of the hoof, below the heel bulbs. Like quarter cracks, these, too, are likely to cause lameness. A shoe that shifts to the side or is too small to support the entire heel to begin with is a common cause of a heel crack. The portion of the heel that overhangs the end of the shoe may split vertically; the edges of the crack will slide up and down past each other with each step.

Overstrikes, when a horse hits the coronary band of a front foot while overreaching from behind, are another common cause of both heel and quarter cracks. “A blow to the coronary band causes a bruise and damage to those tissues,” says Boudreau. “If there’s not enough blood supply in the damaged area that took the blow, this can cause a quarter crack. If the horse overreaches and hits the coronary band, it is usually somewhere in the area between the region of the heel nail and the buttress---the back part of the foot.”

Triage for cracked hooves

When you notice a crack you’d never seen before, you need to make a decision: Do I need to call a farrier right away? Or can this wait until our next scheduled visit? You’ll need to get a close look at it.

In general, the severity of a crack depends upon its depth. Even if they’re long, cracks that are limited to the outer layers of the hoof wall are usually not serious. Most will grow out with the wall and eventually be trimmed off with no harm to the horse. It is, however, a good idea to keep an eye on these blemishes to make sure they do not develop into more significant injuries. 

The cracks to worry about extend deeper into the hoof wall---enough to weaken it. Call your farrier right away if you discover a hoof crack with any of these signs: 

• Instability of the hoof wall. Watch as a friend walks your horse a few steps on hard, level ground. Does the hoof wall shift as the horse places his weight on it? If you pick up the hoof and handle it gently, you may be able to feel the instability on each side of the crack. 

• Draining fluids. Any blood or pus that appears around the edges of the crack may indicate that the fissure has penetrated all the way to the interior of the hoof. 

• Pain or lameness. Any soreness or unsoundness, however minor, is worth investigating. 

• Involvement of the coronary band. Any injury at the coronary band can affect the growth of future hoof wall.

Moshier says he runs into many people who are unsure whether to call the farrier between regular visits to look at a crack. “My answer is that they should call the farrier when the horse is lame as a result of the crack,” he says. If they’re still in doubt, he adds, “I ask my owners to take pictures of the feet with their phone, so they can send a photo to me to ask if it’s something they need to worry about.” 

Treatment options

The basic approach to managing any hoof crack, no matter how serious, is to stabilize the hoof and keep the horse comfortable while new horn grows in and the damaged section is trimmed away---this can take up to a year for cracks that started at the top of the hoof. “Trauma to the hoof, such as an abscess, seldom requires more than good regular trimming and in some cases a properly fitted shoe,” says Heather O’Brien, a farrier from British Columbia. 

Bar shoes are often used to help support cracked hooves. “In most cases the farrier will put clips on the shoe---on each side of the crack---to help prevent movement,” says Moshier. “It depends on the case.” Not all cracks spread apart when weighted---some toe cracks roll inward and “overlap” when the horse puts weight on the foot. “While people tend to think that we need to stabilize that crack by keeping it together, some types of crack repair involve keeping the edges of the crack apart, so they don’t roll inward,” he adds. “Clips, in this case, won’t do much good.” 

More extensive measures may be needed to manage cracks that are unstable. “Lacing,” for example, involves binding the two sides of the crack together using various materials and techniques, including metal plates or steel wires. “If there is a lot of movement in the crack, we might have to lace it together,” says Moshier. “This can be done by putting horseshoe nails across the crack to hold it together or lacing with stainless steel threads.”

Another option is to repair cracks and replace lost hoof wall with products that fill in the gaps with materials such as acrylic or polyurethane. In more severe cases, the patches may be reinforced with fiberglass. “These stabilize the cracks---essentially gluing it to keep the edges stable so they won’t be moving as the crack grows out,” explains Moshier. 

The patch material will then be trimmed away as the hoof wall grows out. “If you apply the patch properly, you can just keep trimming the patch just like the hoof wall as it grows down,” says Boudreau. “If everything works the way it is supposed to, it will grow right on off and then you’ll have a strong, healthy foot again.”

For the most serious cases, when a horse is significantly lame and his long-term soundness is at risk, the farrier will need to work in conjunction with a veterinarian, who can prescribe medications to relieve pain and control infections. In some cases, dead or dying tissue may need to be removed, and x-rays may be needed to look for the position and potential injuries to the coffin bone and other structures within the foot. 

Even as the work to stabilize the hoof is underway, it is important to adjust trimming and shoeing to address any hoof imbalances or other stressors that caused the crack in the first place. “The one thing consistent in all successful recoveries from a crack is the proper balancing of the foot to the horse’s conformation,” says O’Brien. “Without this, the crack will keep returning until proper balance is restored.”

Preventive measures

Simply keeping your horse healthy---with balanced nutrition, not overweight, and plenty of turnout and exercise in good footing---will go a long way toward keeping his hooves strong as well. Beyond that, you can take additional steps to reduce the risk of hoof cracks:

• Stay on schedule with your farrier. Whether the horse is barefoot or shod, regular visits from your farrier are important to keep his feet properly trimmed and balanced in accordance with his conformation. Flares that form at the bottom of overgrown hooves can easily form cracks. “When the hoof wall gets too long it will bend, then crack,” says O’Brien. “Debris from the environment can become embedded in the crack, especially if the horse is barefoot, causing abscesses and even white-line disease.” 

• Use traction aids only when needed. Calks, rims, borium and other traction devices may be invaluable if you often ride on slick surfaces, but they can add stresses to the hooves and legs that can lead to cracks. Your farrier can advise you on the most appropriate shoes for the type of riding that you do.

• Add a supplement, if necessary. A horse whose diet is deficient in important vitamins and trace minerals is likely to have weak, shelly hooves as well as dull, coarse hair. Biotin is the primary ingredient in supplements intended to improve hoof health; many also contain minerals such as copper and zinc as well as amino acids and omega-3 and -6 fatty acids. If you suspect your horse may benefit from a hoof supplement, consult with your veterinarian or an equine nutritionist to assess his diet and create a healthier overall ration. 

• Stop the stomping. Horses harassed by stable flies in the summer will stomp their feet repeatedly--- which can lead to hoof cracks if they’re on hard, dry ground. Fly sprays will repel stable flies, and a number of management strategies can help keep insect populations under control. These flies breed in decaying organic matter, so clean up soiled bedding and manure from turnout areas daily, and treat manure pile with insecticides or larvicides. If flies remain a problem, consider outfitting your horse with fly boots, which cover the legs and prevent the pests from landing on your horse.

• Keep an eye on footing. Galloping over hard ground poses an obvious risk of cracks, but traveling through deep, soft footing also places stresses on the hoof that can cause injury to the hoof wall. Out on the trail, slow to a walk when you encounter ground that is either deep and soft or hard and rocky, and drag your arena frequently to keep the footing uniform.

• Avoid the wet/dry cycle. When hooves get wet, they soften and swell; when they’re dry, they stiffen and contract. Horses can adapt to either condition, but alternating between the two on a daily basis can loosen shoes and cause cracks.

 “It’s not just the horse that’s constantly standing in mud, or a horse that lives in a dry desert environment,” says Moshier. “The biggest problems occur when horses are always alternating, such as going from a stall bedded in kiln-dried shavings to being turned out in the muck or wet pastures.” If your turnouts are chronically muddy, look for ways to improve drainage. Laying gravel in high-traffic areas may also help. 

• Inspect your horse’s hooves daily. Picking out the hooves is an essential part of good horsemanship, but as you do this chore, take some time to inspect the overall health of the hoof: Run your hand over the hoof wall and coronary band to feel for defects. Look for dark spots on the sole, which could indicate bruising. Wiggle the shoe to check for looseness---if you have a farriery tool called clinchers on hand, you can tighten the clinches. If the shoe is on the verge of falling off, your safest option may be to remove it entirely. “I advise people, when cleaning the feet, to pick the white line and clear everything out of it. That’s the area to look at closely,” says Moshier. “Look for any blackness in the white line because that’s a sign of infection.” 

Probably the best advice of hoof crack prevention and management is simple: Get to know your horse’s hooves. As you handle his feet, give the hoof walls a once-over. Also consider taking photographs of your horse’s hooves occasionally; these may help you determine if a crack you’ve spotted is new or if a preexisting defect is getting worse. 

“Talk to your farrier about what is normal for that foot, and what isn’t, and be able to recognize any new cracks,” Moshier says. “I had a client who became very worried about a crack she noticed. I got there and looked at it, and it was a scar type crack from a weakness in the wall. This crack had always been there, but it was the first time she’d seen it.”

Keeping your horse’s hooves healthy and strong requires attentive care. But if you can prevent serious hoof cracks, you’ll give him a solid foundation for a lifetime. 

This article was originally published the March 2016 issue, Volume #474 of EQUUS magazine

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