For thousands of years, horses have evolved by eating large quantities of high fiber forage in the form of range grasses. Because of this, the microorganisms in the horse's large intestine that aid in digestion are those that use portions of fiber to grow. There are some bacteria that are capable of using carbohydrates in the large intestine but these bacteria are much fewer that the ones that break down fiber. Horse intestines are designed to digest mostly forage in small quantities all day long; we wonder why they develop problems when we try to feed them large amounts of grain and put them in stalls. When large grain meals are fed, a portion of the starch can escape the small intestine and enter the large intestine where it is rapidly fermented by bacteria. The scientists at Kentucky Equine Research indicate this fermentation leads to an increase in acid production and this leads to a decrease in pH of the large intestine. When the pH of the large intestine drops, this allows toxins to be absorbed in the circulation that can lead to laminitis and founder. This decrease in pH also kills the normal bacteria that are used to digest forage. All of this can lead to colic, inappetence, and even unusual behavior like wood chewing or stall weaving.
Not all horses have access to a pasture so they cannot be put out on the range, and lots of high performance horses need a high grain diet, so a study was performed feeding a supplement with a specifically designed type of sodium bicarbonate called EquiShure. Feeding this supplement was effective in increasing the pH in horses who were fed high grain diets and could help prevent some of the symptoms seen in these horses.
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