The following is a chapter from Dr J's first book, Maine Horse Doctor : On the Road with Dr J
Gravel is the unusual name for what is probably our most common cause of lameness. It would be rare for any equine vet not to be dealing with a case a week. A horse that is “graveled” might be three legged lame one day and completely sound the next. Many horses recover with no outside help. Even more remarkable is that usually, once a horse is over it, there are no after effects.
In order to understand this lameness and how to deal with it, we have to start with some basic knowledge of the horse’s foot. Pick up your horse’s foot and look at the bottom. The junction between the wall and the sole is called the white line. It’s just like the junction between the wall and the floor in a room. It’s not really a structure in itself; it’s just a place where the wall and the sole meet. In a healthy foot it’s a faint line which is lighter in color than the wall or the sole. Have your farrier point it out the next time he is trimming.
The culprit is usually a piece of gravel that penetrates at that wall/sole junction. The small stone gets wedged in the white line and allows bacteria to enter. An infection may follow. If it is unable to drain out the bottom of the foot, the horse is on his way to becoming “graveled.” Some people think the stone travels up the foot and causes the lameness. It doesn’t. What does travel up is the bacteria and the inflammation that they cause.
The abscess may just drain, or be drained, by your vet or farrier from the bottom of the foot. Often it works its way up the white line inside the hoof wall, following the path of least resistance. When the infection gets up to the sensitive areas of the foot, near the coronary band, the horse will become very lame, sometimes to the point of refusing to put the foot down. The lameness may not appear for days or even weeks after the original penetration. A graveled horse looks and acts like a horse with a broken leg. It hurts. The foot is often warm and there is almost always a very strong digital pulse at the back of the pastern and low ankle. Pressure with hoof testers may cause more pain. If there is some doubt as to the diagnosis, X-rays may have to be taken, and sometimes (but not always) show exactly where the abscess is.
If your farrier or vet cannot get a graveled foot to drain from the bottom, then there are two other ways that the issue is usually resolved. As the infection reaches the top of the wall at the coronary band, it may break open. The skin splits, and smelly watery pus will drain out. Relief comes quickly. To encourage this, soak the foot in a strong solution of Epsom salts. Place the foot in a corded black rubber feed tub and then slowly add water. Once you see that the horse will accept that, add the Epsom salts until you see a little bit undissolved on the bottom of the tub. There is nothing as soluble as Epsom salts, and the more concentrated the solution is, the more drawing power it has. Poultices can also help. Even with these aids, some graveled feet do not open up at the top, and then the third possibility will happen. In these stubborn cases the abscess will slowly be absorbed, and the horse gradually becomes less lame.
Even though gravel is an infection, we usually advise not giving antibiotics. No matter how high the dosage, it is hard to get a therapeutic level. Abscesses tend to get walled off with fibrous tissue, and the medicine is unable to penetrate them. If possible it’s best to avoid using anti- inflammatory medicines such as Bute or Banamine which may make the animal more comfortable. These drugs do decrease the pain, but they also tend to slow down the possible release of the infection from the bottom of the foot or at the coronary band. Although rare, there are cases where the infection becomes very entrenched and severe, and these horses often have to be hospitalized and more specialized procedures done to alleviate the problem. Graveled horses should be current on their tetanus vaccination.
If you have a lame horse for no apparent reason, always check the digital pulse of the foot. A strong pulse as compared to the normal foot is often the best indication that your horse may have gravel. It seems to be a more consistent finding than heat in the foot. If you don’t know how to find and assess the pulse, have your vet show you the next time he or she is in the barn. It is a skill that is easy to learn and one that every horse owner should master. I always ask owners who call about an acutely lame horse if there is a stronger pulse in that foot. If there is, the chances are good that the animal has that strange foot infection we call gravel.