Severe diarrhea cases require supportive care, such as administering intravenous fluids to rehydrate horses. | Photo: Courtesy Chris Tully/Rood and Riddle

Be it due to toxins, infectious agents, or simply diet changes, diarrhea in horses is no laughing matter.

It’’s a nasty, messy bodily (dys)function. And while it might be the source of little boys’ hysterical laughter and the stuff of snickers even among adults, it’s no joke to horse owners. Diarrhea occurs when the intestine doesn’t absorb electrolytes and water normally, instead allowing them to pass out of the body in loose or watery stools. It can be acute or chronic.

While some types of equine diarrhea present little to worry about if watched carefully, others can be life-threatening.

“In humans, diarrhea is generally benign,” says Rose Nolen-Walston, DVM, Dipl. ACVIM (LAIM), associate professor at the University of Pennsylvania’s New Bolton Center, in Kennett Square. “But horses have a rather delicate large intestine that has a very minutely balanced flora of bacteria, and something that disrupts that balance can cause diarrhea even without a particular pathogenic (disease-causing) bug being there. We call that colonic dysbiosis