Q&A: Why Are Abscesses So Tricky?

After news of California Chrome's defection from a run at Royal Ascot was blamed on a hoof abscess, we got to wondering what causes this common hoof ailment, and how it's treated. We sat down with Mitch Taylor, certified journeyman farrier and director of education at the Kentucky Horseshoeing School to learn more about this issue through a farrier's eyes.

First of all, how does an abscess happen? When horses get any kind of penetrating wound, which can allow bacteria to get in, these anaerobic bacteria set up shop inside the blood supply of the hoof. If you get a bruise, for example, fluid leaks out of the vascular beds into the interstitial tissue. What'll happen is, if bacteria gets in there, it will feed on the blood. Bacteria can come in through a puncture wound, or just material getting in through a crack. It can also happen if a nail is inserted improperly.

The hoof is a contained unit, kind of like a ski boot—it's very rigid and doesn't allow space for any inflammation. It doesn't stretch like the skin does. It is skin, it's just made up of keratin rather than collagen, which is what our skin is made of.

The byproduct of bacteria in the foot is gas, and that creates pressure. The pressure causes extreme pain.

Sometimes we hear about a horse getting a bruise that later turns out to be an abscess. How are the two issues different on an up-close level? A stone bruise is any blunt force trauma that the horse's sole or hoof gets when it hits a rock or something sharp—just like when we get a bruise.

Also what can happen is you can get a bruise from the coffin bone pushing down onto the sole [from the inside of the foot]. If you trim the soles really thin like we do in racehorses, you can usually press down with your thumb on the sole and depress the sole. A lot of times when we see a stone bruise actually, we see it in the shape of the coffin bone. Think what happens if the horse was to step on a rock.

Because you've got the hoof up off the ground on a shoe that puts all the weight on the perimeter of the foot, the coffin bone is suspended from the sensitive laminae inside the hoof capsule. So, sometimes when the foot loads the bone descends a little too much.

Are there different types of abscesses? There are two basic types of abscesses: we have a subsolar abscess (in between the sole and the bottom of the foot) which can take place anywhere, including the seat of corn (corners of the foot under the heel) or under the frog. The other type is a subdural abscess, where it's in the laminar bed, on the side of the foot. It is different in that it has to drain from the top of the coronary band—some people call it a gravel.

This is fairly common, right? Wicked common. If you take a look at how many big horses get one of these before a race, it's amazing.

Is an abscess or bruise a sign that a horse isn't being properly cared for? They can happen for a lot of different reasons, but most of the time it's not because of owner neglect. A foot crack could be a different story.

Why are Thoroughbreds at such risk for damage such as this? In the Thoroughbred racehorse, it's a little different. We've got a fairly immature foot—one that's not really finished growing at age two or three. They're soft feet  because when they get to the racetrack, the horses live in a bedded stall and go to the track. They're never on very hard ground, so their feet are 1) a little young and 2) trimmed and shod so that they travel with very little interference, so they are shod with the toes fairly short compared to other breeds. That right there gives a disadvantage towards stone bruises because the foot is not as thick and protected as it could be. It opens them up to blunt force trauma from the ground. Also, we bathe them a lot and soak them in ice buckets a lot. You put that together, and you can have the opportunity for something to bruise the bottom of the foot because the moisture softens the horn.

What does a horse with an abscess look like? Abscess are known for, one day you turn the horse out and everything's good, next day they come hobbling in. They'll change the way they stand. The first thing you should do is find the abscess. Check for a digital pulse, which will be stronger because of the abscess. You can use hoof testers (if you know how) to try to isolate the area on the foot. You'll want to pull the shoes, but if the abscess is around a horseshoe nail and you go pulling that nail back out, it's going to be very painful, so you need a farrier to help with that.

There are lots of old wives' tales about the best way to treat an abscess. What do you recommend? There are a lot of products out there. Epsom salt is great stuff. It's a very good drawing agent. What we've got to do as far as treatment of subsolar abscesses or gravels is we need to first of all locate it, and then we have to make some judgment call on how we're going to treat it. If we feel it's a gravel, one of the symptoms is the coronary band will swell and the hair will stick straight out. You soak it in Epsom salts and put a foot pack on it (something like an Animalintex pad which is boric acid on a thin piece of cotton padding). Overnight, hopefully the abscess will have been drawn out and burst in the pack. Or you can use something called Magna-Paste, or any of the pre-filled poultice wraps like Stayons. The Epsom salts soften the horn up. Once it bursts open, it's a matter of basic first aid, making sure it doesn't get reinfected. Once you get it drained, you feel a huge sigh from the horse.

For a subsolar abscess, we have to actually nick the bottom of the foot and drain it. If you open up a hole in the sole before it's ready to drain, you open up the foot to more abscessation and more foot pain, so you want to make sure you're not going into the wrong area. You can feel it usually underneath there. You may have to give it a day or two to mature, and in that time, it's really important that you don't have the horse stall bound. You want him to have a small area that causes him to walk around because it helps them work the exudates out.

It doesn't hurt to put them on a little bute at this stage – I want them up and walking to get the exudate to come out.

How long is the recovery process? It depends on the location and severity, but a light to moderate abscess they might have them out of shoes in a foot pack for five days.

Any other words of advice for treating an abscess? It's really important that you have trained farriers working on your horses because nowadays there are all these products. If you were to cover up an abscess with a shoe or a pad or something without getting all the bacteria drained, you can have it re-abscess, and when that happens it's always worse.