Older Horses & Chronic Diarrhea in the Winter

My older horse has chronic diarrhea in the winter. What can I do for him?
Runny manure is a common winter problem in older horses. It seems that the large colon is traumatized by the roughage component of a hay diet and has difficulty in maintaining a healthy bacterial population. As a result, the feed is not properly digested and moves through the colon too quickly for water to be reabsorbed from it. When summer comes, much of the diet is composed of soft grass which they can tolerate more easily. “Winter squirts”, as we call it, is a problem because the horse is not gaining maximum benefit from his diet, as well as the awful mess that results.
As this is a problem encountered very frequently in older horses, I think that many people will be interested in information on this topic so I will go over my diagnostic and treatment approach. A thorough physical exam, fecal test, and bloodwork is a good starting point to identify any underlying conditions that may predispose the horse to this problem. Diseases such as Cushings, salmonella, parasitism, and intestinal cancers can all cause intermittent diarrhea. The teeth and oral structures should be evaluated for loose or diseased teeth, and anything else that would interfere with proper chewing of roughage. Occasionally, a urinalysis or abdominal tap (to assess peritoneal fluid) may be performed to search for low grade infection or abnormal cells. While it is a long shot, gastroscopy can be performed to detect gastric ulcers.
Diet plays an important role in managing the loose manure. I try to keep the horse on a combination of beet pulp, well soaked hay cubes, and a complete senior diet, avoiding long-stem hay altogether. This can be challenging as it is often hard to keep weight on these guys. The addition of a product called “Bio-Sponge” to the ration can help to bind irritating toxic byproducts of digestion in the colon, and I also recommend the use of yogurt and probiotics. We have had success with putting the horse on low doses of metronidazole, which is an antibiotic that is active against harmful gut bacteria, as well as omeprazole, which seems to help with colonic irritation in addition to gastric ulcers. Older horses can have a lowered resistance to intestinal parasites, so extra deworming may be indicated even if your barn is on a regular program. Careful use of low-dose dexamethasone will reduce inflammation in the intestine but this must be used with care and is not ideal if the horse also suffers from Cushings. In general, a solution is found through trial runs of these strategies and medications. It is a very frustrating condition and typically reoccurs every winter. Some horses respond very well to treatment while others stubbornly continue to squirt all winter despite our best efforts.

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