When “Just Slobbers” Becomes Something More

Why Horse Owners Should Take Excessive Salivation Seriously

OKLAHOMA STATE UNIVERSITY EXTENSION

STILLWATER, OKLAHOMA

Excessive salivation in horses – commonly referred to as slobbers – is a condition most horse owners have seen at least once. For years, the standard advice has been simple: remove the horse from the source, ensure access to water, and the problem will resolve within a day. In most cases, that guidance holds true. However, a recent experience discussed on the Extension Horses Tack Box Talk Series reminds us that slobbers can occasionally escalate into a much more serious situation.

What Causes Slobbers?

Slobbers is caused by ingestion of certain molds that grow on legumes, most commonly red clover, but also white clover and, in some cases, alfalfa. The condition is associated with black blotch disease, a mold that forms on the underside of legume leaves, particularly during hot and humid conditions. This mold produces a compound called slaframine, which stimulates excessive salivation when consumed by horses.

Unlike typical hay mold associated with baling wet hay, black blotch disease is not always obvious and can be difficult to detect. It often develops in dense clover patches where moisture is retained, creating a microclimate that favors fungal growth.

Pasture and Hay: A Key Takeaway

Most horse owners associate slobbers with pasture exposure. However, one important takeaway from this discussion is that slaframine remains active in hay for up to 10 months. That means horses can develop slobbers even when they are completely off pasture and consuming stored forage.

In this case, slobbers occurred in October in Minnesota, when a horse was eating hay harvested just 60–90 days earlier. The hay came from a familiar field that had been used for decades, underscoring that even well‑managed forage systems can pose occasional risks under the right environmental conditions.

A Case That Changed the Narrative

The turning point in this conversation came from a real‑world case involving an older, semi‑retired performance horse. The mare developed classic slobbers – copious, continuous salivation – but initially appeared otherwise stable. Because slobbers is typically considered benign, the hay source was not removed right away.

Over a short period of time, a combination of factors created a perfect storm:

• Advanced age
• Hot, unseasonably dry weather
• A thicker hair coat
• Continuous fluid loss from salivation

The horse ultimately became severely dehydrated, showed signs of disorientation, and required overnight hospitalization for intravenous fluids. Bloodwork revealed dangerously elevated dehydration markers, placing stress on the kidneys and cardiovascular system. Fortunately, with prompt veterinary intervention, the mare made a full recovery – but the experience fundamentally changed how slobbers was viewed.

Why Dehydration Is the Real Risk

Slobbers itself is not toxic. The danger arises when horses lose fluid faster than they can replace it, particularly in hot weather or when access to water is compromised. In this case, dehydration was not immediately obvious on physical examination, yet bloodwork showed a serious underlying issue.

This highlights an important point: horses may not always outwardly “look” dehydrated, even when significant physiological stress is occurring.

Management Recommendations

If you observe slobbers in a horse, especially excessive or persistent salivation, proactive management is critical:

• Immediately remove the suspected feed or pasture source
• Provide unlimited access to clean, fresh water
• Monitor hydration closely, particularly in older horses or during warm weather
• Inspect hay for heavy clover content and manage clover‑rich bales separately
• Consider diluting suspect hay with older forage or non‑legume hay
• Seek veterinary advice if signs worsen or do not resolve quickly

It is also important for producers and horse owners to recognize that testing hay for slaframine is not routinely available. Visual inspection and attentive management remain the most practical tools.

The Bottom Line

Slobbers is usually a mild, self‑limiting condition – but “usually” does not mean “always.” This case serves as a valuable reminder to trust your observations, act early, and avoid complacency, even with conditions we think we know well.

Horses are individuals, and their responses to forage, weather, and stressors can change over time. Staying vigilant – without panicking – can make the difference between a minor inconvenience and a medical emergency.   ∆

OKLAHOMA STATE UNIVERSITY EXTENSION