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Study Examines Prevalence of Quarter Cracks in High-Performance Horses

Like equine athletes in all disciplines, Thoroughbred racehorses face hoof-related challenges, including quarter cracks. In an effort to better understand this hoof wall abnormality, researchers investigated the incidence, clinical presentation and future racing performance of Thoroughbreds with quarter cracks over a nine-year period.*

A quarter crack is a full-thickness failure of the hoof capsule between the toe and heel that may extend the entire height of the hoof, from coronary band to ground. The separation often results in unsoundness due to instability of the hoof wall or infection of the deep dermal tissue, though many horses remain free of lameness despite the presence of a quarter crack.

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Quarter cracks are thought to arise for many reasons: innate hoof weakness; improper hoof balance; injury or trauma to the coronary band; or infection of the corium, part of the internal vascular network of the hoof. Poor farriery may contribute to hoof imbalance, which could contribute to crack formation. A common finding among horses with quarter cracks is sheared heels, an unevenness of the heels that causes unequal weight-bearing on the bulbs and creates a shearing force absorbed by the hoof capsule.

During the nine-year study period, just over 4,500 horses in a training center were followed. Seventy-four horses had at least one quarter crack during the study period. Twenty horses had two or more quarter cracks. Almost half of all horses with quarter cracks were lame at the onset of the defect.

An overwhelming number of cracks occurred in the front hooves and there was a proportional difference in the number of cracks in the left rather than right front hooves. Most of the cracks came about on the inside of the hooves.

The quarter cracks identified in this study were treated in various ways, though the principle treatments included corrective shoeing with a heart-bar shoe, wire stabilization, and the use of epoxy or acrylic. Treatment goals centered around correcting the hoof imbalance and eliminating uneven movement.

Racing performance following treatment was available for 63 of the 74 horses. Of the 63 horses, 54 horses had at least one start after treatment. When compared to control horses, there was no significant difference in the number of career races, career wins and career placings for horses with quarter cracks.

As mentioned previously, horses genetically predisposed to weak hoof walls might be susceptible to quarter cracks. Racehorses are generally well-nourished, as trainers know the importance of sound nutrition in conditioning an athlete. Aside from high-quality forage and fortified concentrates, horses inclined to poor-quality hooves should be given a research-proven hoof supplement. Biotin should be a primary ingredient in the supplement, but other ingredients will further support hoof health. A high-quality hoof supplement also contains methionine, iodine and zinc.

*McGlinchey, L., P. Robinson, B. Porter, A.B.S. Sidhu, and S.M. Rosanowski. 2020. Quarter cracks in Thoroughbred racehorses trained in Hong Kong over a 9-year period (2007-2015): Incidence, clinical presentation, and future racing performance. Equine Veterinary Education 32 (Suppl. 10):18-24.

Snap, Crackle, Pop: What Creaky Joints Mean

It's not unusual for equine caretakers to hear their steed's joints pop and crack when they move. Though alarming, these noises are generally nothing to worry about. Joints make noise when the joint capsule is stretched and releases gas from the joint fluid very quickly. This is the same process that allows people to “crack” their knuckles; after a bit of time, the same joint can be cracked again.

The most-mobile joints tend to be the loudest: knees, hocks and stifles. Joints in the neck or back may also pop, especially when the horse is stretching.

Cracking doesn't mean that a joint is tight, loose or out of alignment. If the horse is sound and comfortable, clicking joints is nothing to worry about.

Decoding Hoof Cracks

Horse owners can attest that the old adage “No hoof, no horse” is one truest about equine care. Any defect in a hoof wall can be worrisome as the health and integrity of the hoof wall is imperative for overall horse health. Some issues can look concerning, but be non-issues, while others may require intense care to rectify.

Here are some types of cracks and what the level of concern they should elicit:

Though hoof cracks can look scary, small, vertical cracks that start at the ground and extend only an inch or so up the hoof wall are of minor concern. The farrier will most likely take care of these when he or she is out next.
Horizontal cracks less than an inch wide that start at the coronet band and grow down are typically the result of a minor injury to the coronary band that briefly inhibited hoof production. It's rare that intervention is needed for these cracks; they will grow out on their own. \
Vertical cracks at the bottom of the hoof that wrap around to the underside of the hoof and involve the sole could be more than just a superficial defect. If it looks like any other structures than just the hoof wall are involved, this could become a significant issue.
Long, vertical cracks that don't ever seem to grow out are a sign that a hoof is chronically unbalanced. Even if the crack is thin, it is worth having a conversation with the farrier to see if a new manner of trimming or shoeing may be necessary.
Cracks that flex and open each time the horse takes a step, cracks that bleed or cracks that make a horse lame requires an immediate call to the veterinarian and farrier. Both professionals will need to work together to resolve the issue, but time is of the essence and these cracks need to be addressed immediately.