Why Do Horses Foam At The Mouth?

It’s not uncommon to see a horse foaming at the mouth during riding lessons, horse shows and horse races, trail rides and other riding events. While you might think this is a cause for concern, the fact is foaming at the mouth is not usually problematic and may even be a positive sign. In this article, we discuss the reasons why horses sometimes foam at the mouth and describe the circumstances in which this may be a negative. Read on to learn more.

What Is Happy Foam?

What Is Happy Foam?

If a horse is relaxed while being ridden, he or she may foam at the mouth. This can be a sign that the horse is accepting or “on” the bit. This is a positive. This means that everything is well-fitted, and the horse is able to receive the rider’s communications clearly.

In dressage, this is often called “happy foam”.

Sometimes if a horse is fitted with a bit made of copper, it can induce heavy salivation and drooling. This can look like foaming at the mouth. This is not problematic except that your horse may become excessively thirsty and dehydrated.

A horse with a dry mouth may be tense through his upper body, neck, mouth and lips. This can lead to poor horse/rider communication.

A nervous horse may be fitted with a bit with a roller. This gives the horse something to do as he plays with and fidgets with the roller. This can facilitate foaming at the mouth.

Is Foaming At The Mouth Always Good?

A horse being properly ridden with a correctly fitted bit should be able to close its mouth comfortably and swallow excess saliva easily.

A bit that is not properly fitted and/or an unskilled, heavy handed rider may also cause excessive drooling and pain, along with rider inability to communicate effectively with the horse.

If a horse’s foaming at the mouth is caused by an improperly fitted bit and/or a poor rider, this is a problem that should be corrected promptly. This is especially true if the foam is pinkish or red. This is blood, and it means that injury has occurred.

It is also worth noting that the bit may be improperly fitted because the horse has a dental problem or a musculoskeletal deformity. Any excessive drooling and/or foaming at the mouth may be a sign of dental problems, such as:

  • Bite out of alignment
  • Plaque and Tartar
  • Bleeding Gums
  • Missing teeth
  • Loose Teeth
  • Bone spurs
  • Gingivitis

Be sure to have your horse’s teeth examined, cleaned and floated annually. If a horse you are considering buying foams at the mouth and/or drools excessively, be sure to have your vet examine the animal’s teeth and mouth.

Why Do Horses Foam At The Mouth?

Hard Riding Can Cause Foaming At The Mouth & Lathering

A horse that has been overworked may foam at the mouth. This is also problematic. Overexertion should be stopped before it begins. A horse who has been overworked needs to be relieved of his or her tack, given hay and water and a comfortable, safe place to rest.

In cases of overexertion, you may also see foamy perspiration (lather). This, along with foaming at the mouth caused by overexertion) is caused by a protein called latherin. The horse secretes this slippery substance because it causes sweat to slide easily off the body and assists with cooling.

Latherin is also present in saliva and is released in response to stimulus from the bit and also when a horse drinks, eats and chews. It aids swallowing and digestion.

What If A Horse Foams At The Mouth While Resting?

If a horse is foaming at the mouth or drooling excessively without any apparent stimulation, this may be a case of hyper-salivation.

If this is accompanied by other signs and symptoms, such as coughing, wheezing, behavior changes, lethargy or bloody saliva, consult your vet promptly. It could be an indication of mouth ulcers, blisters, choking, injury or some other serious problem.

Mouth blisters may be caused by a virus called vesicular stomatitis. In addition to blisters and sores around the mouth and muzzle, your horse may run a fever, lose weight, lose his or her appetite and display lameness.

Call your vet right away to have blood tests performed to confirm (or rule out) this virus. Follow your vet’s instructions for quarantine and care until the virus runs its course.

If your horse is on pasture and suddenly starts slobbering during a very hot, dry weather, suspect clover slobbers. This is a problem that is caused by a type of fungus (Rhizoctonia) that thrives in red clover and white clover and other types of legumes (e.g. alfalfa).

It is also possible for your horse to get the slobbers from infected clover that has been baled up in hay. Always inspect hay for signs of mold before presenting it to your horse.

The slobbers will not usually hurt your horse, but a slobbering horse looks unsightly and may cause neighbors and passersby alarm.

Some Illnesses Can Cause Foaming At The Mouth

If you don’t keep your horse up to date on vaccines, he or she could easily contract rabies from any infected animal (e.g. dogs, cats, skunks, raccoons, foxes, bats, etc.) Be sure your horse receives all necessary vaccinations at his or her annual physical.

In the United Kingdom, the bacteria, botulism, can cause a malady known as equine grass sickness or wooden tongue. Other illnesses that can cause drooling and foaming at the mouth include a virus called Borna disease and another called equine viral arteritis.

Toxins & Contaminants Can Cause Foaming At The Mouth

Heavy metals in soil and/or water can cause excessive drooling. Test your pasture soil before allowing your horse access to the grass each spring.

A regular testing schedule is recommended. Have your water tested, and take steps, such as replacing old, corroded pipes, as needed to keep heavy metals out of the water.

Toxins can also cause drooling and foaming at the mouth. Avoid using herbicides in or near your pasture. Be sure that all products you use on your horse are safe for equines, and avoid allowing products to come in contact with your horse’s eyes, nose and mouth.

All-In-All Foaming At The Mouth Is Not A Cause For Concern

While there can be negative reasons for horses foaming at the mouth, more often than not, this is just a sign that your horse is comfortable and relaxed.

If your horse is fitted properly with a comfortable bit (especially a copper one) and you are riding at a proper pace in a relaxed and skillful manner, you can expect “happy foam”.

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