Winter Diarrhea in Horses

Winter Weather Means Feeding Hay
During the switch to a 100 percent hay diet in the fall of the year is when many horse owners first notice that some of their horses are getting loose manure. The situation can quickly evolve into a management mess where one or more horses are so loose they can spray fecal material on the walls of the stall when they pass manure. Winter grooming becomes a major challenge for those who care for these horses as they struggle to keep tails hocks fetlocks and equine clothing clean and free of encrusted manure.  

Why do some horses get chronic diarrhea or the liquid squirts when on winter hay and why dont all the horses consuming the same forage in the barn get it? What can you do about this frustrating condition?
Equine Digestion Refresher
In order to understand what might be happening in the hindgut of the horse with chronic diarrhea we should first briefly review the digestive system of the horse as well as the digestive processes that happen there. Horse are defined as nonruminant herbivores and hindgut fermenters. Ruminants sheep goats and cows are herbivores as well but the forage they eat is largely digested through fermentation by a group of beneficial microbes that live in the first stomach called the rumen. The rumen is situated in the foregut of the ruminant meaning forages the animal eats go through the rumen fermentation process first before they hit the true stomach and enzymatic digestion.
Carbohydrate sources such as starch and sugar are readily digested in the enzymatic environment of the foregut where they are broken down to glucose units which can be absorbed directly into the blood stream. Absorption of glucose arising from digestion in the foregut causes a rise in blood glucose of the horse stimulating insulin