Diarrhea in horses is a symptom, not a diagnosis. It can develop when the intestine is inflamed, normal digestion is disrupted, or water is no longer absorbed and retained in the usual way. A horse passing softer manure after a feeding change presents a different situation from one producing repeated watery diarrhea, refusing feed, or becoming weak. Formed manure with a separate stream of fecal water is different again. The important questions are: What has changed in the man