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EquiSearch’s Ask the Vet: Runny Manure

Horse manure that is too dry or too wet is a sign of an unhealthy intestinal tract. Find out how to treat it in this Ask the Vet by Dr. Joyce Harman on

Question: I have a horse who has a loose stool occasionally and squirts liquid. It is runny (like water) and green. The vet and other horse people tell me he is wormy. I have given him a five-day Panacur regiment, one month later ivermectin, and then a week after that three days of Safeguard. Is it possible he has a nervous stomach or something? My vet here doesn't seem concerned about it. His hind end and legs are stained from the squirts, and he doesn't smell good.

© Stacey Nedrow-Wigmore
The consistency of your horse

Answer: This is an excellent question since the horse's gut is such a problematic part of its life.

Abnormal manure, whether too wet (diarrhea) or too dry indicates to me that the intestinal tract is not healthy. The intestinal tract contains bacteria and protozoa designed to digest food, manufacture vitamins and make minerals available. The intestinal environment is a miniature eco-system where each player has a place and a job, like a symphony, and if any piece is out of place, the whole is affected.

The normal pH of the healthy intestinal tract changes from acidic in the stomach and upper small intestine, moves towards neutral in the lower small intestine and becomes slightly alkaline in the large intestine. The bacteria grow on dietary fiber in the digestive tract, not in the intestinal wall. Consequently when fiber is deficient, the bacterial population is not healthy. The balance of the different bacteria keeps the pH in the correct range. When antibiotics are used they kill off both the good and bad bacteria. Other drugs, poor nutrition, stress and lack of quality hay all can contribute to poor gut bacteria health. (See EquiSearch's Ask the Vet: Horse Ulcers)


The basic way the intestines work is to receive food into an acidic stomach where protein starts digestion and several important minerals are prepared for absorption (calcium, magnesium, manganese, iron, zinc and to some degree selenium). In the small intestine protein digestion is finished, fat digestion takes place and some carbohydrates are absorbed. The cecum is the big fermentation vat where the fiber (hay, grass) is broken down by microbial action into ingredients horses can absorb. The large intestine's main job is to regulate the amount of water that ends up in the manure.

With incomplete digestion anywhere along the whole intestinal tract and/or poor quality feeds, the pH can become altered starting a spiral of less healthy bacteria and poorer digestion. If the food passes through too fast, which often occurs when horses are fed grain with little roughage, the large intestine cannot keep up its water regulation job. Also, nutrients are poorly absorbed so the horse becomes less healthy.

Some horses have food sensitivities which can cause a mild (or even severe) inflammation in the digestive tract. These could be allergies or just reactions to certain foods. Many processed grains move too fast through the digestive tract and often contain a variety of byproduct ingredients that a sensitive horse may have trouble with.

So, what to do when your horse is showing excessive amount of fluid or other indications of poor gut function? The first thing to do is to add some probiotics (good bacteria) to help repopulate the gut. You may or may not know your horse's past history of drug or antibiotic use. Only use high quality probiotics since many products have very little active ingredients left by the time you buy them. There are several on my website that I have used with success.

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