Ultimate Book of Horse Bits

The horse’s mouth and head are well designed for carrying a bit. The bit itself sits on the bars of the mouth. When a bit moves, it makes contact with a number of pressure points that vary according to the type of bit, the way the bit is attached to the bridle, and the fit of the bridle as well as the bit. The pressure points range from minimal to acute. The choice of bit very much depends upon which pressure points are most important for the rider to accomplish his riding and training goals, and upon the preferences of the horse and his way of going.

To understand how bitting developed and how it functions today, it helps to understand the horse’s functional anatomy. Early horses’ teeth and mouth structures were similar to those of today’s horses. Eohippus—the horse thought to be the predecessor of modern equines—was a smaller animal, and so it had fewer teeth and a shallower jaw line. Mesohippus, which lived 25 to 40 million years ago, developed with a gap between the front and back teeth as his face became more elongated.

Nature designed the horse’s mouth for grazing in his sometimes harsh environment. The design of the horse’s mouth and his agile lips allow him to move dirt aside to find the most nutritious forage. The process begins with the incisors, at the front of the mouth. The horse uses these teeth to grab and tear the grass out of the ground. Saliva is created once anything foreign enters the mouth cavity, which then softens the forage so it can be ground by the molars and prepared for digestion.

As it turns out, the anatomy of Equus callabus (the horse we know today) did us, their future domesticators, a great favor. The very convenient gap between the front incisors and the molars of the equine skull is the crucial structure for any and all discussions of proper bitting. This gap, called the bars, is in a perfect place for seating a bit.

We don’t know how man came to figure out that the space between the molars and the incisors would make a good place to put a rope you could use to steer a horse, or that putting something in a horse’s mouth and then using it to direct his head would ultimately make him a “rideable” horse. That question remains unanswered, just as we’re not sure who and what events led early man to figure out that rubbing flint together would create fire. Both inventions were crucial to humankind’s development.

Nature created a nice space for the bit—between the molars and the front incisors.

At first glance, horses’ heads look the same: soft nostrils, the slit of the lips, the whiskers. Look a little closer, however, and notice that every horse has a different mouth. Try the following experiment: Find three or four horses who will let you stick your fingers in their mouths. Take your index and second fingers and slide them gently into each horse’s mouth at the bars, where the bit normally goes. Make a note of what you feel inside. Are you feeling the roof of the mouth? How much space is there between the top of the tongue and the palate? How wide is the horse’s mouth? Now pull back his lips and measure how long the bars are. Are they the same on both sides? How much does the length of the bars differ from mouth to mouth? How do the teeth look? Are they the same as those of other horses? Then do the same experiment from the other side. What kinds of differences do you notice?

No doubt you’ll find that each horse is different in some way; you’ll also find that one side of a horse’s mouth may be different from the other. You might also notice different colors in the horses’ mouths—dark patches or bright pink or almost red spots. Peel back the lips and notice how the teeth fit together. Does each horse have the same bite?

Just like humans, only without the benefit of modern-day orthodontic treatment, horses have all kinds of different mouths. When I visited the Herm Sprenger bit factory in Germany, Heinz Baumann, who has been designing bits at Sprenger for decades, said he planned to become a bit fitter when he retired. Although he was half joking, Baumann’s become something of that already, working with top European and American riders to build new bits for their problem horses. So why, then, aren’t there more loriners who make bits specifically for your horse’s mouth? After all, there are plenty of custom saddle makers in the world.

Besides being logical, if hideously expensive in today’s production-based economy, having bits made to order would seem to solve many of the problems riders face with their mounts, especially considering how vastly different horses’ mouths are. Unfortunately, custom bit makers would encounter many dissatisfied clients because the majority of bit problems are actually training problems.

Nonetheless, the individuality of the horse’s mouth has been the subject of recent study by Sprenger’s university partners as well as a number of U.S.-based veterinary researchers. Sprenger worked with the Hannover Anatomy Institute in Hannover, Germany, to determine how the width of the bit impacts the horse’s mouth and how the position of the bit affects the anatomical structures of the mouth. They used a group of thirty-one three- and four-year-old horses. Researchers measured the distance between the bit and the palate both with the horses at rest and with rein contact. The study noted that the choice of the proper bit very much depends on the size of the horse’s mouth, and that the old adage about thick bits being softer than thin ones may not apply to those horses with thick tongues and low palates. In that case, the thicker bit may be more severe and uncomfortable.

Continuing research has found that the distance between the tongue and the palate can vary as much as an inch between horses. The research has also found that horses can have as much as a 5 mm difference between the right and the left sides of their mouths.

Interestingly, these studies discovered that the size of the horse’s mouth has little to no correlation to the size of the horse. The large horse does not necessarily have a large mouth. Anecdotally, my event horse, Volare, was 17.1 hands and wore an astonishingly large size 86 blanket. When it came to his head, though, he had a rather delicate jaw and muzzle; he wore a regular size 4¾-inch French link snaffle. Later I used his same bit on my delicately built, 15.2-hand filly. While most bits today are made for what we can call a bell curve of horse sizes—where the majority wear a bit that ranges from 4½ inches to 5½ inches—several manufacturers are making smaller and larger bits that are fit proportionately. For many years, pony bits were just sized-down versions of horse bits, and the same was true for oversized draft bits. The better quality manufacturers, however, are resizing and re-proportioning their over- and under-sized bits to fit the larger and smaller mouths. Because of the sensitivity of your horse’s jaw bones, tongue, and palate, it is not enough to buy a size 5 bit because that’s what you think your horse will wear. You have to know how to hang that bit in his mouth, and how much room there should be between his lips and the bit ring. As such, measuring your bits and knowing how to tell when a bit fits properly is very important to your horse’s comfort.

Next time the equine dentist comes to call (which should happen twice a year, ideally), ask if you can put your arm inside the horse’s mouth (obviously he should be nicely tranquilized and wearing a locked speculum). Your arm, depending on your size, will likely go in up to your elbow before reaching the back of the throat. Despite the astonishing length of a horse’s mouth cavity, it is still possible for certain types of bits to interfere with both a horse’s back teeth and his swallowing and breathing mechanisms.

Consider the horse’s throat anatomy: To simplify what is a very complex system, there are two “pipes” in a horse’s throat. One goes down the esophagus and the other down the trachea. The esophagus leads to the stomach while the trachea leads to the lungs. Unlike humans and dogs, who can breathe either through their noses or their mouths, the horse breathes exclusively through his nose. Deep in the gullet, the soft palate opens and closes like a door when the horse swallows, allowing food to enter the esophagus. According to Dr. Robert Cook’s studies of bitting, a horse can either breathe deeply or swallow, but it cannot do both at the same time.

A horse that’s quietly grazing in the pasture has his mouth open while he eats. His nostrils take in and expel air, and his mouth is wet from saliva. He gathers up a lot of material before he swallows, hence the length of his mouth cavity. The tongue, one of the most important pieces of the bitting equation, is attached to the hyoid bones, which are attached to the jawbones. The hyoid bones are in the shape of the bottom half of a rectangular box deep in the throat, in which where the tongue rests. The hyoid bones prevent the tongue from dropping into the throat. The hyoid apparatus is compressed slightly when the poll is deeply flexed.

A study performed by researchers at the University of Michigan measured how a bit affects swallowing. Horses were wearing a bitless bridle, a jointed snaffle, or a Myler bit (see page 53) and had side reins attached for poll flexion. The researchers then measured the number of times the horses swallowed while cantering. None of the bits prevented swallowing, but horses did swallow less frequently in certain kinds of bits. The study also noted how having a bit in the horse’s mouth creates different behaviors, from a quiet, closed mouth to using the tongue to raise the bit within the mouth.

Dr. Cook notes that placing a bit in a horse’s mouth switches on his digestive system. When he takes something in his mouth, it stimulates his salivary reaction. Although some researchers believe it is the flexion of the horse’s poll while bridled that compresses the parotid gland and stimulates salivation, causing the horse to wet his mouth in anticipation of food, others argue that putting anything in the mouth—bit, grass, or water—stimulates salivation. That, in turn, prepares the horse for swallowing by raising the soft palate so nothing gets into his airway.

Some horses are much more sensitive about certain parts of their bodies—their polls, for example, may not tolerate the pressure of the bridle’s crown piece. They may have sensitive ears, lips, or cheeks. They may prefer the taste of a certain metal over another metal. Like eighteenth-century loriner Benjamin Latchford wrote, there’s a “key” for each horse’s mouth. Finding what he likes will take a lot of experimentation and thoughtful riding.

The salivary glands provide the lubrication necessary to move food from the front of the mouth to the epiglottis, where swallowing takes place. The glands discharge the enzymatic fluid that helps the food break down. Salivation signals the digestive tract to get ready for food.

When a horse chews, it triggers the salivary glands to prepare the food for digestion and creates saliva. Introducing a bit—a foreign object in the mouth—creates the same response. Horses that are relaxed and happy in their bits will generally chew softly, creating a wet mouth, while those who are tense or tight may lock down on the bit and not create much saliva at all.

There is some controversy in the science about whether a soft, salivating mouth is necessary for a responsive horse—some horses simply don’t chew when they have a bit in their mouths. Others slobber when they’re upset or in ill health. In some equestrian disciplines the horse’s chewing isn’t necessarily a sign that they’re well trained. In others it’s considered a sign of relaxation and “acceptance” of the bit.

Dr. Cook notes that racehorses or other sport horses that bleed through the nose during exertion are actually being partially asphyxiated by their own tongues, which have drawn back in their mouths in retreat from the bit and in preparation for swallowing. In so doing, the root of the tongue cuts off the airway and causes partial asphyxiation.

Another problem horses face because of the tongue’s relationship to the rest of the body is tension in the neck. Dr. Joyce Harman notes that the hyoid bones are actually the origination of the two most important neck muscles that attach to the sternum and the inside of the shoulder. Thus a tense tongue will cause a stiff horse.

Drs. Clayton, Manfredi, et al. note that the relationship between salivation and bit is difficult to pinpoint. Excessive salivation, they write, can actually be induced by the bit and exacerbated in some cases by a horse’s inability to swallow often enough. Dr. Cook contends that salivation and a busy mouth can actually be signs of discomfort. In an effort to remove the bit from his mouth or move it away from an area of pain, he may be excessively busy with his mouth, chewing and fussing and playing.

What Clayton found goes against the common belief that bitting increases swallowing. The fact that swallowing frequency did not increase in the bitted horses versus those in bitless bridles or halters proves that salivation may actually be the result of another physiological action—flexion of the poll, for example. She concluded that the presence of a bit doesn’t prevent swallowing when horses canter with flexed polls.

THE MOUTH ITSELF

The inside of your horse’s mouth is where most bits have an impact: the front teeth (incisors), the major palatine foramen (palate canal), and the bars of the mouth, which are the long spaces between the canines or tushes in male horses or the third incisors in females and the wolf teeth (if they are still present) or the molars. The bars become knife-edge sharp the closer you get to the front teeth.

A view of the incisors. This horse, despite being twelve years old, has not lost two of her baby teeth.

Without going into too much detail about equine dentition (there are other books for that), the teeth and their proper care are key to comfortable bitting. Generally, male horses have canine teeth just behind the front incisors, but female horses may only have a small bump, if anything at all, in that location. The bars are between that bump and the molars. This area should be smooth and uniform, running from three to four inches depending on the horse. The upper jaw has the same toothless area, but it is somewhat shorter in length than the lower jaw. An additional tooth sometimes grows just before the molars—it’s a small, pointed tooth known as a wolf tooth. Not all horses develop them, but they can be quite sharp. Occasionally, they can also interfere with the bit or be irritating to the horse. No matter how well a bit fits a horse, there will always be some wearing on the teeth.

Equine archaeological specialist David W. Anthony and his colleagues, in trying to determine how to assess possible bit wear in the earliest horses, studied the premolars (the teeth closest to the bit) of both domestic and feral horses. They determined that horses that have been ridden with a bit have four clear types of tooth damage, even if they’ve been ridden with a rope or other natural material. The enamel of the first cuspid is scarred on the cheek, tongue, and front sides of the tooth. The teeth exhibit small fractures on the surface and the movement of the bit over these fractures causes even more irregular damage. Lastly, the front of the tooth has been worn down. Given such a large amount of damage to the teeth, one can only imagine how an ill-fitting metal bit feels against the much more fragile structures of the tongue, the bars, and the lips.

If you compare the teeth of a horse that has never worn a bit and the teeth of one that has, you can quite easily see the results. The second and third premolars have likely become worn down. The more severe the rider’s hands, the more wear on those sets of teeth. Keep this image in mind during our exploration of bits.

A dental care professional should examine your horse’s jaw and his bite at least once a year. A poor bite, where the top and bottom teeth don’t come together evenly, can make wearing a bit quite uncomfortable, or cause the horse to move his jaws side to side. It can also be the root of a tongue problem. While there are no orthodontics for horses, a veterinarian or equine dentist can shape the teeth so the jaws fit more evenly and repair a bite problem.

Like our own, horses’ teeth change substantially over time, with an immature horse of three or four still losing his milk teeth, and a twenty-year-old horse having much more sloping teeth. In between, horses develop markings on their teeth that can help determine their age as well as their dental health. Understanding how horses’ teeth and mouths change can help riders understand how important it is to consider different bit choices as their horses age in both chronological and training years.

A dental care professional or properly trained veterinarian should examine your horse’s teeth at least once a year. Here, Dr. Mark Meddleton of Meddleton Equine in Algodones, New Mexico, performs a thorough dental exam.

Besides varying in length, the horse’s upper and lower jaws are different widths. The upper jaw is wider than the lower jaw, a fact that may not have an impact on the actual bit choice, but may determine the size of the bit you choose. If you examine a horse with his mouth closed, you’ll notice his upper lip is slightly wider than the lower one, reflecting his wider upper jaw. Also, the horse’s jaws have basically no muscle—meaning there is no protection from pressure between the jaw bones and the nerves. Consider the feeling of metal on bone; that’s what your horse feels from the bit. The nerves are close to the surface. Pressure is translated instantly from rein to brain. Additionally, the nerves residing in both upper hard and soft palates are relatively exposed, meaning that they, too, are highly sensitive to pressure and pain.

The anatomy of the horse’s mouth is rather obvious: the bit goes in the space between the molars and the incisors, and rests on the tongue. The edges of the bit can press against the bars, the lips, and, depending on the type of bit, possibly the roof of the mouth (the palate).

The equine mouth and head are extremely sensitive, thanks to the location and sensitivity of the facial nerves. There are twelve cranial nerves that control many of the functions and senses, such as taste, sight, hearing, and touch. They are the same nerves that control a horse’s chewing and salivation mechanisms. Both of those mechanisms, as well as swallowing and the flexion of the head and neck, are directly correlated to the pressure on the reins and the bit. The mouth, jaw, and lips are thin structures, and the nerves are quite close to the surface.

The trigeminal nerve—or C5—is probably most important in the equine head when it comes to bitting. This nerve originates at the pharynx, splits into three branches (hence trigeminal), and follows the length of the mouth both on the top and the bottom of jaw. The nerve commands sensation from the jaw; it also commands the muzzle, upper jaw, and nasal cavity. The trigeminal nerve is said to be responsible for much of the feeling in a horse’s muzzle and mouth. It is, in essence, his facial command center.

Scientific studies note that these nerves are so sensitive they can react to light, even though they are under the skin (a condition that may be one cause of a chronic condition called head-shaking). Researchers have found that an ordinary rider with light hands exerts hundreds of pounds of pressure per square centimeter (or 0.15 inch) on the bit. The horse feels this pressure acutely in the trigeminal nerve upon which the bit is sitting.

Other areas of sensitivity are the corners of the horse’s lips. The skin here is most sensitive, designed so that the horse can use his lips to find food in otherwise barren landscapes. His lips are like little radar antennas, with his whiskers helping out. A horse who has his whiskers shaved off for the first time may have difficulty finding his food. Watch a horse as he grazes in what appears to be a relatively unfertile pasture: he’ll use his lips to gently wipe away the surface soils to expose the shoots of grass and other forages down below. This hypersensitivity is one of the ways horses were able to survive in the wild.

The horse’s brain sits in a small “box” just behind the ears. The poll, a knobby point on the top of the horse’s head, protects the brain box and is also covered by the very thinnest layer of skin. When the rider takes a feel of the reins, the pressure on the bit radiates up the cheek pieces and over the top of the horse’s poll via the bridle’s crown piece. A horse ridden in a leverage bit, such as curb or other long-shanked bit, will feel more pressure on the poll than one ridden in a regular direct-pressure (snaffle) bit.

Everything about a horse’s head—command central—is designed to be related to his “fight or flight” decision-making process. So when pressure is applied to the horse’s head, he reacts by either yielding to or fighting against that pressure. A well-trained horse and rider pair have developed good communication, and the horse relaxes and accepts the bit.

When early bits were designed, man was most interested in training methods related to pain—early bits, as noted above, included spikes and harsh mouthpieces, largely because man didn’t know any better. Today’s bits, while certainly much more evolved, can have the same impact in the wrong hands. Xenophon’s early wisdom stressed the use of leg aids and the seat as well as the very light hand. As noted, he was well ahead of his time.

Horses with ill-fitting or misused bits definitely show the signs of pain, many of which are misunderstood as training or “bad horse” issues. Injuries caused by bits can include ulcers forming on the bars, bruising, lacerations, or other signs of trauma. A look at a skull of a bitted horse shows the bone spurs that frequently develop. Horses in pain throw their heads or shake them, bolt, buck, rear, or toss their heads violently as a result of pain in the mouth (remember fight or flight?). A painful problem in the mouth can also quickly radiate down the neck to the spine and even to the haunches.

This horse cannot close his mouth over the bit, indicating that the mouthpiece is too wide for him.

The bridle and bit exert pressure on the head in five different sensitive areas beyond the mouth cavity. An ill-fitting bridle can rub the horse’s cheekbones (an area that, like the bars of the mouth, has little cushion between the skin and bone, making it extremely sensitive). An ill-adjusted or fitted curb strap on a double or curb-type bridle can cause a horse pain in his chin groove. A too-small bit can rub the horse’s lips and his cheeks. It also loses its effectiveness, because it is restricted into a straight-bar type of action. The center joint (in either a double or single-jointed bit) is no longer flexible.

If the horse is wearing a bit that doesn’t fit, he doesn’t understand what the rider is asking for. A too-large bit that slides side to side in the mouth can damage the tongue, the palate, and the lips. There is no stability in the mouth, and the connection with the rider is lost. It feels like a shoe that’s too big. Such painful experiences cause the horse to dislike the bit and may lead to longer-term behavior problems or habits that are extremely difficult to break. For example, a horse ridden with a tight hand may try to cushion his bars against the bit by sticking his tongue out and slipping it between the bar and the bit’s mouthpiece.

Understanding bitting takes a keen knowledge of the inside of your horse’s mouth, and his particular anatomical attributes. An equine veterinarian who will let you look inside your horse’s mouth and will explain your horse’s unique structures is invaluable to the bitting process. You’ll be able to determine the size of his mouth, the depth of his palate, the thickness of his tongue and the length of his bars. All are key to choosing the right bit.