Forage Buffering Capacity Relevant in Gastric Ulcer Prevention

The capacity of feeds and forages to counteract changes in gastric pH (their buffering capacity) plays an important role in the prevention of gastric ulcers in horses. Alfalfa hay has been shown to be more effective in reducing the severity of ulcers in horses by providing superior buffering capacity compared to grass hay.

Gastric ulcers are common in performance horses, affecting more than 90% of racehorses and 60% of show horses. Most ulcers occur in the upper portion of the horse's stomach and are primarily the result of prolonged exposure of this tissue to gastric acid. The upper half of the equine stomach does not have a mucous layer and does not secrete bicarbonate onto its surface (which is the process by which the rest of the stomach is protected from ulcers). The only protection this portion of the stomach has from the ulcer causing agents gastric acid and pepsin comes from saliva production and the buffering capacity of feed.

The "epidemic" of ulcers seen in performance horses is a man-made problem resulting from the way equine athletes tend to be fed and managed (ulcers are much less prevalent in unexercised horses maintained solely on pasture). Meals of grain or extended periods of fasting lead to excessive gastric acid output without adequate saliva production.

Additionally, production of volatile fatty acids (VFAs), particularly butyric acid from the fermentation of grain in the stomach makes the upper portion of the stomach more susceptible to acid damage.

Horses secrete acid continuously whether or not they are fed. The pH of gastric fluid in horses withheld from feed for several hours has consistently been measured to be 2.0 or lower (researchers have noted that when the pH in the stomach is less than 4.0, it's more likely that VFAs can cause damage). Meanwhile, horses that received free-choice timothy hay for 24 hours had mean gastric pH readings that were significantly higher since forage consumption stimulates saliva production, which protects the stomach.

There is growing evidence that the type of hay fed to horses significantly impacts acid neutralization and gastric ulcer incidence. A team of researchers at the University of Tennessee reported a study in which six horses with gastric cannulae (stomach tubes used to sample stomach contents) were fed both alfalfa hay and concentrate, or bromegrass hay without grain supplementation.

The researchers found that feeding alfalfa hay and concentrate increased the pH of gastric fluid and reduced the number and severity of ulcerations in the upper stomach compared to feeding the diet of bromegrass hay. Saliva production was not measured in this study, but the results suggested that the buffering capacity of the alfalfa and/or concentrate was greater than for grass hay.

A different study from Texas A&M University researchers suggests the incidence of ulceration was compared in horses fed a pelleted concentrate along with either Bermuda grass hay or alfalfa hay. Gastric endoscopy was performed at the beginning of the study, and each horse was assigned an ulcer severity score using a grading system ranging from zero (no sign of ulceration) to four (penetration of the submucosal lining).

The group found that relative to feeding coastal Bermuda grass hay, feeding alfalfa hay reduced ulcer severity scores in horses with gastric ulceration, and prevented ulcer development in 11 of 12 (92%) horses fed alfalfa hay that did not have ulcers, whereas only 25% (3 of 12) of the horses without evidence of ulceration fed coastal Bermuda grass hay did not appear to develop ulcerations.

It's believed that alfalfa hay provides greater buffering capacity compared to coastal Bermuda grass hay for several reasons. First, alfalfa contains higher protein and calcium levels, both of which buffer gastric acid. Also, alfalfa cell wall contains certain indigestible compounds such as lignin that give it a greater buffering capacity than grasses.

Article reprinted with the permission of copyright holder Kentucky Equine Research (KER). Visit for more horse health and nutrition information.

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