Everyone has heard of forging, crossfiring and scalping, but not everyone’s clear about the differences among them. More often than not, the horse is simply said to “interfere.” That makes it clear the horse has a “gait abnormality,” but it tells you little about the causes and consequences and what you can do about it. That’s what really matters.
Crossfiring and forging are common. Crossfiring occurs at the walk and the pace. In most cases, you will hear that characteristic metal “click” as the shoes contact each other.
Forging occurs at the trot and again is usually accompanied by the sound of metal on metal when the horse is wearing shoes. If the forward movement of the foot is more delayed, the horse may reach up and hit the bulbs of the heels, leading to chronic bruising or even drawing blood.
Interference where the front foot hits the back, instead of the reverse, also occurs at the trot. Horses with low, ground-covering gaits may interfere foot to foot (this is difficult to differentiate from forging) or to the coronary band. With more animated trots, the impact may occur on the inside of the hind pastern or fetlock, sometimes even higher up, on the cannon bone or even the hock.
Regardless of the specifics of where the horse is contacting himself, the basic problem is that the horse moves either too slow in front or too fast behind. All strategies for correcting these problems use this principle.
When a horse moves clean, he’s said to have smooth gaits with no contact between the moving legs. If he interferes somehow, the reason is usually due to conformation, soundness and/or shoeing. The most common conformation problems are:
Short Back/Disproportionately Long Legs: This horse simply has trouble staying out of his own way.
Sickle Hocks: The sickle-hocked horse will usually travel farther under himself than a normal horse, has less hock action and a decreased backward extension of the leg.
Straight Shoulder: A horse that is straight through the shoulder has a short, choppy way of going in front. If this horse happens to use his hind end well, he may be inclined to forge or crossfire.
Horses with hock pain often shorten their stride behind to some degree. They may still be more likely to have problems with interference though if they also show another common movement change with hock pain — a tendency to bring the leg farther underneath them and toward the midline. The horse may also be in a hurry to unload the painful hock(s), thus speeding up his action behind.
Far more common than hind end contributions, however, is foreleg pain. A horse with pain in a front leg will usually compensate by taking more weight on the opposite front. He will also decrease the time the painful leg spends in full weight-bearing, unloading that leg more quickly. He therefore shortens the time the good leg spends in the air and also keeps it on the ground longer than the painful leg. Putting this in the framework of the mechanics above, the horse is speeding up the painful leg and slowing down the good one. He is therefore more likely to “catch” himself on the good leg but go cleanly on the painful one.
Whether or not this occurs depends in part on what extent the horse is using the other common compensatory technique for dealing with pain in one foreleg — to switch some of the weight-bearing load to the hind leg on the same side.
If he divides the extra weight evenly between the opposite front and the hind on the same side, the slowing effect on the front leg will be balanced by an equal slowing of the opposite hind leg and he won’t crossfire. He probably won’t forge either because he will slow the other hind leg as well to keep the gait even.
If the horse doesn’t evenly distribute the extra weight he is taking off the sore front leg, putting most of it onto the sound front leg and leaving the hind end largely uninvolved, he is more likely to forge or crossfire. The lesson here is that if your horse starts crossfiring or forging on one side for no obvious reason, look for a source of pain in the front leg opposite from the one he is hitting.
Many horses only show this if you let their feet get too long. The longer toe and extra weight in front further slows down the front end, while the longer toe behind can give just enough extra length to the foot to make it actually connect whereas it would not if the toe was shorter.
Because the horse’s front end naturally carries a larger percentage of the weight, even a horse that is unloading a sore leg both onto the opposite front and onto the rear will be shifting more of the load to the opposite front. This is often just enough of a difference to cause the horse to start to crossfire or forge when his toes get too long.
This logically brings us to hoof care. Horses with a short back or overly “leggy” conformation are predisposed to interfering in the first place. Simply letting the horse’s feet get too long may be all it takes for the problem to surface.
A long toe slows the foot’s breakover, as does the added weight of a too-long foot. All other things being equal, this has a greater effect on the front because the horse bears more weight up front. It is therefore slowed more than the back, making the horse more likely to hit.
Conversely, the solution for a horse that interferes like this is to reverse the situation — the farrier speeds up the action of the front feet and slows down the hind. For horses with poor conformation, keeping the feet trimmed to correctly do it.
Making the foot/toe shorter (and keeping heels proportional, of course) will lighten the foot and speed up the action up front. Using a lighter shoe on the front may have the same effect, as does a rolled toe/rocker-motion shoe. If this doesn’t work or if the change in how the horse moves up front is not acceptable to the owner, the farrier will focus attention behind.
The least drastic corrections behind squaring the toe or, sometimes, setting the shoe back from the front edge of the hoof wall. The latter correction doesn’t change anything. The horse still interferes. All it does is eliminate the obvious clicking sound, since the front shoe is impacted by the hoof wall and not the shoe.
If these solutions fail, the next step is a modification that will provide some additional holding/delaying action to the movement of the hind legs, including switching to a heavier shoe, a light application of borium, studs/caulks, using a creased shoe, heel caulks or trailers.
One of these solutions will likely fix the interference problem but, as usual, there is a price to pay. All of the holding/stabilizing options, especially borium and caulks, place more strain on the muscles, ligaments and joints of the hind leg as they require more force be exerted to move the leg forward and a jarring when it lands.
The Role Of The Rider
An unskilled rider can cause interfering — especially if the horse previously didn’t interfere. Improper weight distribution or an unsteady seat can cause the horse to compensate to keep his balance. It’s like you trying to walk with a 20-pound weight in one pocket. Almost any horse would interfere with such an imbalance.
Conv ersely, a balanced, experienced rider can transform a horse showing minor interference problems, like forging, with only slight adjustments. Before you consider exotic shoeing options consult with your trainer to be sure you are not part of the problem or have a friend ride the horse to see if there’s a difference.
The Role Of The Horse
We already discussed how conformation problems can cause interference. Attitude, namely laziness, is another possibility. Many horses will interfere with almost every step when just ambling in and out of the pasture but have no problems at all when you wake them up a bit under saddle or doing ground work.
As a rule, interference problems that are worse at the walk or with casual riding and are corrected by making the horse work in a balanced frame are not serious and should be handled by proper training alone. Those horses that get worse with speed or extended gaits require other forms of intervention.
Interference may be caused by something as simple as a horse being a little lazy, a poor rider or going too long between trims. It could also signal underlying conformational problems or lameness. Left uncorrected, secondary soreness, resistance and deterioration of gaits can occur. If your horse is interfering, do a careful, systematic check for the causes, involving your farrier, vet and trainer in coming up with a plan for correcting it.