How to Stop Your Horse's Strange Bit Behavior

Does your horse seem uncomfortable when bridled? It could be due to a variety of issues.
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Q: I am 15 years old and have had horses almost all my life. I have been working with a Shire named Magnus who is 11 years old and hasn’t seen a saddle or bit for about five years. I finally got him used to my English saddle and he’s fine with putting the bridle on, but he doesn’t like the bit or isn’t used to it. When he is wearing his bit, he opens and closes his mouth (making a popping noise) and his mouth will foam. What should I do?

Credit: © DUSTY PERIN When trying to determine the cause of a horse’s bit discomfort, be sure to check that both his bit and bridle are properly adjusted.

BESS DARROW, DVM, Certified Equine Dentist 


A: First, you need to identify what is causing the problem. Issues that might lead to both the popping sound and the fussy behavior fall into two categories: physical and mental. Some common physical sources of discomfort in the mouth include dental issues, abnormalities of the jaw or temporomandibular joint (TMJ), stiffness in the poll and problems related to the type or fit of the bit or bridle. If Magnus isn’t suffering from any of these physical problems, you may need to consider a mental component to his behavior. Perhaps he never learned to accept the bit properly or had a bad experience with a bit in the past. Whatever the cause, you should be able to find a solution that makes the bit experience much more comfortable for him. 

Start by ruling out physical issues. The foam you’re seeing may be salivation caused by the normal action of mouthing the bit. Horses ridden properly through (so they’re using their entire bodies in a relaxed, swinging manner) naturally produce a certain amount of saliva. Excessive, shaving-cream-like foam, however, may indicate a dental problem, such as a broken tooth, abscess or sharp enamel point causing discomfort in his mouth. Ask a dental specialist (a certified equine dentist or veterinarian with advanced training in equine dentistry) to examine Magnus’ mouth thoroughly. A horse his age could have developed any number of dental problems caused by irregular wearing of his teeth and the development of sharp hooks or points. The popping sound you’re hearing could be the result of a tall, overgrown tooth striking another tooth.

Your horse may even have an ulcer on the inside of his cheek, a tumor or a foreign body lodged in the roof of his mouth or between his teeth. If you notice that he has bad breath or a smelly discharge coming from his nostrils, he may be suffering from a tooth infection. Routine floatings don’t always catch and correct these problems, so it’s worth investing in a specialist’s more-comprehensive exam. 

A less-common cause of the popping sound could be TMJ disorder, which affects the joint where the lower jaw hinges to the skull. It may become painful and inflamed due to repeated stress, injury, arthritis or physical deformities. A horse with tooth problems can develop a TMJ disorder secondarily if he changes his chewing patterns to avoid a painful tooth or if an overgrown tooth causes his bite to be lopsided. This joint is also very closely associated with the poll, so any tension or pain in the poll (resulting, for example, from a bridle that pinches behind his ears) could potentially be misdiagnosed as TMJ pain. An accurate diagnosis may require the use of X-rays or ultrasound. In the absence of a definitive diagnosis, if your dental specialist still suspects that Magnus is suffering from a TMJ disorder, he or she may recommend a trial series of anti-inflammatory medication or joint-block injections to further diagnose or rule out the condition. 

A much more common cause of mouth discomfort is the bit itself. Is Magnus’ bit clean (free of rust and dried-on spit and debris)? Is it properly fitted and positioned correctly in his mouth? A poorly fitting bit can cause a horse to chomp his teeth, cross his jaw and salivate as he attempts to avoid the discomfort. Finding a bit wide enough for a draft horse is not always easy. A good way to check the fit is with one of the simple bit-measuring devices, such as BitFit or Bit Sizer, available through tack stores and online retailers. If the bit is too high or low in his mouth, it may be bumping into his teeth, which can be painful. Every horse’s mouth conformation is different, so ask your dental specialist to help you position Magnus’ bit in the best place for his mouth.

Also experiment with different bits. Some horses like thicker or thinner bits. Some seem to prefer certain styles and types of metal. I recommend starting with a simple snaffle. Alternatively, some horses are most comfortable without a bit. There are numerous bitless bridles available on the market today. Every horse is an individual, so the same bridle may not work on every horse in your barn. Ask your riding instructor to help you try different options until you find something that works for Magnus. Don’t forget to check that the bridle fits him properly and is not pinching his forehead or behind his ears. 

If you’ve eliminated all of the above concerns and concluded that Magnus’ problem is mental rather than physical, treat him like a green horse and go back to basics. Five years out of work is a long time, and he may not be as confident as he was earlier in life. Whether he has had a previous negative riding experience or simply limited knowledge, take your time with this part of the training so he is happy and not anxious about his new job. Try working just on groundwork without tack for a few weeks—with your instructor’s guidance— to strengthen your relationship. Then reintroduce the tack, removing the reins from his bridle, putting it on underneath his halter and letting him stand with the bit in his mouth while you supervise him. Gradually increase the time he wears the bridle over a number of days, allowing him to get accustomed to the feel of the bit without having to respond to any rein pressure. When he seems more comfortable with it, you can start riding again, being careful to make all of your rein aids clear but gentle. 

Whatever problem (or problems— there may be more than one contributing to Magnus’ behavior) you identify and solve, you’ll be glad you paid attention to him and took his needs seriously—and so will he!


Dr. Bess Darrow is both a veterinarian and an International Association of Equine Dentistry-certified equine dental technician. An avid proponent of providing proper dental care to all horses, she operates her North Central Florida-based business, Tune Ups Veterinary Equine Dentistry & Wellness Services, with a fully equipped mobile equine-dentistry trailer. She offers educational lectures and demonstrations to horse organizations and provides in-depth research on her website, www.tuneupsequine.com, on a variety of topics, including bit fit and function. An experienced eventer, dressage rider and foxhunter, Dr. Darrow also trains horses and teaches Pony Club students.

This article originally appeared in the July 2013 issue of Practical Horseman.

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