“Slobbers” or hypersalivation in horses.
The term “slobbers” might conjure up images of a St Bernard drooling on a hot day which would be normal but if you see your horse slobbering then it is time to get concerned. There are really 2 main ways a horse will have excessive salivation and that is either by producing too much saliva or because the saliva cannot be swallowed normally. The horse has 3 pairs of salivary glands that can produce almost 40 liters (10 gallons) of saliva every day. That’s a lot of liquid to swallow.
The most common cause of not being able to swallow the saliva would be choke. This condition occurs when food material or a foreign object gets lodged in the esophagus or pharynx and causes an obstruction. Usually these horses will act agitated with their neck extended and may gag or retch. Sometimes the saliva is coming out the nostrils as well. This often occurs in horses that like to bolt their feed down fast.
Some abnormalities of the oral cavity can cause excess salivation. If the abnormality in the mouth causes pain such as oral abrasions, foreign bodies such as wire or wood in the tongue, a fractured mandible, oral abscesses, masses or dental disease then the body’s response is to produce more saliva and the horse may be too painful to swallow well. Often with these conditions the horse will either not eat or show difficulty eating by tilting its head to the side, balling up feed in the side of the mouth or dropping feed.
In other cases the salivary glands are tricked into producing more saliva then necessary. One common cause is by eating clover contaminated with a fungus known as Rhizoctonia leguminicola. This fungus produces a chemical called slaframine which stimulates the nervous system of the horse to produce more saliva. These horses usually do not have and trouble eating and return to normal once off of the clover but some can develop other problems like sensitivity to light and liver disease.
Another group of chemicals capable of producing increased saliva are called organophosphates and are typically found in pesticides. Horses exposed to them may also show signs of frequent urination, diarrhea, colic, difficulty breathing and small pupils.
Infections can cause hypersalivation. The most concerning but also very rare of these is Rabies. The rabies virus can infect the nerves of the salivary gland and cause them to produce too much saliva. Horses with rabies can act many different ways and show many different signs. The bad news is that rabies is 100% fatal but the good news it is 100% preventable with vaccination. Rabies is highly contagious and fatal to humans also so do not come in contact with any animal suspected of having it. Bottom line is vaccinate your animals for rabies.
There are numerous less common causes of excess salivation including toxins (heavy metals, lead), fractures (bones at the base of the tongue or inner ear), infections (strangles, equine viral arteritis, Actinobacillus lignieresii), neurologic (trauma to nerves) and Gastrointestinal (ulcers, tumors, liver disease).
Most of the causes of excess salivation are correctable but the condition should not be ignored and you should seek professional advice on how to approach your horse’s condition.