Scientists Consider Irritable Bowel Syndrome in Horses

Horses could suffer from irritable bowel syndrome (IBS) like humans do, hypothesized human gastroenterologist John Hunter, MD, from the Gastoenterology Research Unit at Addenbrooke's Hospital in Cambridge, United Kingdom.

In humans, IBS is extremely common and thought to affect up to 15% of the population at some point in their lives. Symptoms include recurrent abdominal pain accompanied with changes in bowel habit (either diarrhea or constipation).

There are several causes of IBS, and food intolerance is thought to cause approximately 50% of human IBS cases, explained Hunter in his overview of IBS. Intolerance to dairy products, celiac disease (gluten sensitivity), or fermentation of food in the colon are potential mechanisms of the condition.

In horses, structural carbohydrates of plants are normally fermented in the colon by microorganisms. In contrast, fermentation of nonstructural carbohydrates (e.g., due to excessive feeding of grain) increases the risk of both colic and laminitis.

While it is known that some bacteria such as Clostridium perfringens, Clostridium difficile, and Salmonella are associated with colic in horses, no studies have specifically evaluated changes in the microflora (normal population of microorganisms residing in the gastrointestinal tract) of horses fed an excess of nonstructural carbohydrates.

"This is potentially very important, as not every horse fed excess grain develops colic or laminitis," wrote Hunter.

Human studies have found that the microflora of people with IBS is not normal. "Metabolomic techniques" that analyze complex chemical mixtures in biological fluids identified significant differences in chemical compounds produced during fermentation of food in IBS patients. It has been hypothesized that these chemicals "may give rise to diarrhoea and to increased pain on colonic distension," according to the report.

Since alterations in microflora appear to be important in IBS, the use of metabolomic techniques "may provide a suitable way forward to identify such changes in the horse's gut and thus help to identify more accurately those at risk and to provide opportunities for the development of improved treatment," concluded Hunter.

Hunter's overview, "Do horses suffer from irritable bowel syndrome?", was published in the December 2009 edition of the Equine Veterinary Journal.

The abstract is available on PubMed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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