Decreasing Risk of Enterolithiasis: Hay Type and Pasture

An enterolith inside a horse's colon, which can cause colic
Enterolith after being removed form a horse's colon

An enterolith before and after surgical removal at Washington State University. This particular one weighed 3.6 kg and measured 20 cm around. The horse survived and recovered well.

Too much alfalfa, too little oat and grass hay, and limited access to pasture grazing are important factors that put horses at risk for developing enterolithiasis (intestinal stones).

Enteroliths are composed of a crystalline mineral that forms one or more concretions in various regions of the colon. Enteroliths have the potential to cause colic.

According to Diana Hassel, DVM, PhD, Dipl. ACVS, ACVECC, assistant professor of Equine Emergency Surgery/Critical Care at Colorado State University's College of Veterinary Medicine & Biological Sciences, "Previous studies suggest that breed, feed, and various other environmental management practices can contribute to enterolithiasis in various geographic areas such as California."

This study was designed to compare colicky horses with and without enteroliths to identify potential risk factors for the condition.

Between April 2001 and June 2003, 61 horses with enterolithiasis and 75 horses without the condition presented to the University of California, Davis Veterinary Medical Teaching Hospital for evaluation of colic.

A comprehensive statistical analysis revealed that feeding 50% or more of the diet as alfalfa, less than 50% of the diet as oat hay or grass hay, and lack of access to pasture grazing on a daily basis were significantly associated with enterolithiasis. Specifically, horses receiving more than 50% of their diets as alfalfa were 4.7 times more likely to have enteroliths, while horses receiving less than 50% of their diet as either oat or grass hay were five times as likely to develop the condition. Finally, horses with limited access to pasture grazing were 2.8 times more likely to be diagnosed with enterolithiasis.

In horses at risk for developing enteroliths, the authors recommend eliminating alfalfa, feeding grass or oat hay, and allowing daily access to pasture grazing.

The study, "Evaluation of dietary and management risk factors for enterolithiasis among horses in California," is scheduled to be published in an upcoming edition of Research in Veterinary Science. Contributing authors were Hassel; Aldridge, BVSc, PhD, Dipl. ACVIM; Drake, PhD, and; Snyder DVM, PhD, Dipl. ACVS.

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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