Classic Empire is the latest in a long line of horses to miss training or skip a race due to a hoof abscess. Hoof abscesses are relatively common and seem to impact a horse on the trail for a classic race every year. California Chrome, Melatonin, Shared Belief, Game On Dude, and Texas Red have made news the past few years for coming up with an abscess.
Abscesses happen when bacteria works its way into the internal structures of the hoof through a crack, nail hole, bruise, or a weak hoof wall. As an infection develops, more pus is produced, which puts pressure on the inside of the hoof, causing pain. Some abscesses may come on slowly, with the horse galloping a bit stilted or just not moving smoothly. But a horse with an acute abscess may come up suddenly three-legged lame from pain so intense it cannot put weight on the abscessed foot. Eventually, the infection will work its way to the surface and “pop,” relieving the pressure, but causing a small crack in the hoof which must be kept clean and dry until it heals.
Steve Norman, one of the top farriers in the Thoroughbred industry, said the location of an abscess dictates the pain level it will cause. An abscess in the lining of the hoof wall, called a gravel, is painful as it tracks upward through the lining until it breaks out the coronet band at the top of the hoof and releases the pressure. But a subsolar abscess is much more painful because it involves the entire sole of the foot, so there is no area of the foot where the horse can bear weight comfortably.
“Some horses can get a gravel and never go lame,” Norman said. “It can track up the white line, and where they get the most pain is when it gets real close to the coronet band, and then it bursts out. As soon as it pops out, the pressure is off.
“The worst abscess is a subsolar abscess,” he said. “The infection does not track up the wall, it goes underneath the sole. That is the most painful because the body weight is on top of that abscess. The pressure is overwhelming.”
Horses in training are not the only ones who deal with abscesses from time to time; retired horses, especially broodmares, can be susceptible too.
“The most common abscess is what these broodmares get, being barefoot and heavy in foal,” Norman said. “The foot is basically water-logged in the green grass and on the wet ground.”
The common denominator for abscesses is exposure of the feet to a wet environment. For racehorses, this includes muddy racetracks, puddles they must walk through on the backside, daily baths or just hosing off the horse's lower legs, and painting oils on the foot. A soft foot is more susceptible to penetration by a foreign object that can cause an infection and to bruising that results in an abscess. A bruise causes a hematoma (blood pocket) that creates inflammation and further damages the sensitive tissue.
“With that type of abscess, you might have to open it up to drain it and relieve the pressure,” Norman said. “Then you go through a process of soaking everything out and then the process of drying it out.”
Many products are designed to dry out abscesses, including CleanTrax and Magna Paste, which is a commercial version of the tried-and-true Epsom salt poultice. Animalintex and mudpack poultices also work well.
Norman said one mistake horsemen make is overuse of oily hoof preparations.
“What happens when you use any kind of oil, especially on the face of the foot, it leaks down into the nail holes, and it saturates the wall because the wall is made of a thousand straws put together. These are called tubules, and when you saturate those tubules, they become weak and start to deteriorate and the hoof wall starts to fail under concussion. So too much of that is not good.”
Treatment for an abscess depends on its location and severity. Norman advised horsemen to consult a farrier and follow up with a veterinarian, then follow their instructions. He stressed that although the initial diagnosis is important, diligence in following their instructions is crucial for a good resolution.
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