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Clover Fungus Causes Slobbers in HorsesBy Kentucky Equine Research Staff · July 23, 2015

If your horse drools excessively—and you’ll know because saliva will pour from its mouth when it yawns or accepts the bit—the culprit is likely nutritional. What should you do? Simple: head to the pasture or haymow and look for red clover.

A specific fungus, Rhizoctonia leguminicola, affects many varieties of red clover. This fungus produces an alkaloid called slaframine. Also called black patch disease, the fungal infection is visible on leaves as small dark blotches. Usually, the undersides of leaves are affected first, and then the fungus spreads to other parts of the plant.  The fungus thrives in moist, humid environments. Experiencing a rainy summer? Be on the lookout for diseased red clover.

The most widespread sign of slaframine ingestion in horses is hypersalivation.

“As long as horses have access to a clean water source, there will likely be no other notable side effects of slaframine intake,” said Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research (KER).

“If, on the other hand, a horse does not have access to water, dehydration might sneak up on a horse that is producing and spilling excessive saliva, especially in hot, humid climates,” she said.

Once horses are removed from the red clover, saliva production usually returns to normal.

Baled red clover hay can be infected with the fungus and its alkaloid slaframine. As storage time increases, however, slaframine content tends to decrease.