Slobbers in Horses

Causes, Treatment, and Prevention

Horse with slobbers.
A horse with Slaframine Toxicosis. Image: K. Blocksdorf

If you notice your horse drooling profusely during cool and damp weather, the excessive salivation is likely slobbers or slaframine poisoning. Slobbers is caused by Rhizoctonia leguminicola, the fungus found on vegetation that produces the drool-causing slaframine compound. Slobbers symptoms are usually limited to the slobbering itself, but complications may arise if the condition goes untreated. Slobbers should go away on its own and can be prevented by keeping your horse away from vegetation that may be infected with the fungus. The only necessary treatment for slobbers is changing your horse's food source.

What Is Slobbers?

Slobbers, or slaframine poisoning, is the excessive drooling that happens to a horse after ingesting Rhizoctonia leguminicola, the fungus that produces slaframine. This fungus is most commonly seen in red clover, white clover, alsike clover, and alfalfa. The slaframine activates the salivary glands, causing the horse to hyper-salivate. Although non-life-threatening, the horse's hypersalivation can last several hours to several days. Effects begin within hours of the horse ingesting the infected plant but can be easily resolved with the plant's removal or the horse's removal from the area where the plant grows.

Symptoms of Slobbers in Horses

While the symptoms of slobbers are generally mild, prolonged exposure to slaframine can cause your horse to feel discomfort or lead to complications. Symptoms will become apparent within hours or days of ingestion, so treat your horse swiftly to prevent further discomfort. Drooling is symptomatic of several serious diseases in horses, so take your horse to the vet for a definitive diagnosis.


  • Excessive salivation
  • Colic, diarrhea, and bloating
  • Choking

Excessive Salivation

Excessive salivation is the clearest (and sometimes only) indicator that your horse has slobbers. This will probably look like thick drool hanging from your horse's mouth throughout the day. Excess saliva is hard to ignore, so if you notice it, eliminate the foliage around your horse that may contain slaframine. If the excessive salivation does not subside, take your horse to the vet.

Colic, Diarrhea, and Bloating

If your horse's slaframine poisoning is neglected, it may become more severe and lead to symptoms beyond drooling. These symptoms include colic, diarrhea, and bloating.


A horse can choke or suffocate on its excess saliva in some cases. Although rare, it is necessary to address your horse's slobbers before potentially life-threatening complications present.

Causes of Slobbers

Fortunately, the causes of slobbers are limited and straightforward. Recognizing the causes will help to prevent your horse from developing slobbers.

  • Ingestion of slaframine: The only way a horse can get slobbers is by eating a plant infected with the fungus, Rhizoctonia leguminicola, that creates slaframine. It also occurs in stored, dry hay. These plants commonly include red clover, white clover, alsike clover, and alfalfa.
  • Weather conducive to growth: Plants infected with Rhizoctonia leguminicola thrive in the cool and damp climates of spring and fall. Be mindful of the vegetation around your horse during these months and climates.

Diagnosing Slobbers in Horses

A slobbers diagnosis begins with an examination of the suspected infected plant. With a microscope or the naked eye, your vet can examine your horse's food source for signs of Rhizoctonia leguminicola fungus. This examination can be done using cultures and chromatography on hay thought to contain slaframine. Additionally, swabs from a horse's mouth or milk may be examined. A diagnosis will be made by correlating your horse's symptoms and exposure to affected fungi and hay.


No treatment for slobbers is necessary except for changing the horse's food and limiting its access to pastures that contain infected fungi. Mowing the pasture can help control infected plants and promote healthy regrowth. Since the growth of the black patch fungus is dependent on weather, some years will be worse for slobbers than others. It may be harder to detect and eradicate affected pieces in the hay. The toxicity of the fungus will decrease as hay ages, so it may be a matter of waiting several months before feeding the existing hay again. In the meantime, hay replacement is best.

Prognosis for Horses With Slobbers

Most horses recover quickly without treatment so long as access to the infected plant is restricted. If your horse's slobbers is untreated for a long time and complications develop, visit your vet for an expert opinion.

How to Prevent Slobbers

There's very little that you can do to prevent slobbers other than limiting access to vulnerable vegetation during cold, wet weather. It isn't practical to try to remove alfalfa and clovers entirely from your pastures, as they make a valuable contribution to your horse's nutrition. Monitor your horse's health and pay attention to what it eats year-round.

  • What is making my horse slobber so much?

    If your horse is excessively salivating, it has likely been ingesting slaframine, a compound found in vegetation infected with fungus. Slaframine, or "slobbers," will cause your horse to drool.

  • Is slobbers harmful?

    Slobbers is typically not harmful. As with any health abnormality, treat your horse swiftly to prevent further complications.

  • What plants cause slobbers?

    The compound slaframine is commonly found on plants like red clover, white clover, alsike clover, alfalfa, and hay.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Slobbers or Slaframine Poisoning in Horses. Ontario Ministry of Agriculture, Food, and Rural Affairs.

  2. Slaframine Toxicosis in Animals. Merck Manual.