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Preventing Equine Gastric Ulcers - How Forage Buffers Acid

Gastric ulcers are erosions of the stomach lining caused by gastric acid. It is estimated that 50 to 90 percent of domestic horses have ulcers. They can develop in as little as 24 hours and recur in 24 hours respectively. The pain is stressful, which can further exacerbate ulcers. The most common causes of gastric ulcers are lack of forage and stress. Thankfully, as owners, we have some control over both causes.

Read on to learn how and why gastric acid causes ulcers - and what you can do to help prevent ulcers from occurring.
The Equine Stomach - Upper & Lower Regions

Understanding the Equine Stomach

The equine stomach is divided into two regions - 1) the lower (glandular) portion, and 2) the upper (non-glandular) portion. Ulcers can develop in either region.

The lower portion produces gastric acid - and mucus - which helps to buffer the acid.  The upper portion has squamous epithelium – similar to our skin - which offers no protection, making it even more susceptible to damage by gastric acid.

Horses Produce Gastric Acid 24/7 - Saliva is Key to Buffering

Equines produce gastric acid 24/7 in preparation for constant food uptake. Why? Physically and mentally they are designed to have access to forage 24/7. Chewing activates saliva production (an alkaline substance), which buffers the gastric acid.  It's a perfect balance if we follow nature's design.

In nature, horses will voluntarily take breaks to sleep and rest for periods of time, typically no longer than an hour. In domestication, involuntary periods of time without forage can be physically painful and mentally stressful. ​Mental and physical experiences are synonymous in that each has an influence on the other. 

According to Martine Hausberger, PhD, director of the Laboratory of Animal and Human Ethology, a branch of the French national research center (CNRS) and the University of Rennes:
“It is well-known that horses are trickle feeders that would naturally consume a semi-continuous supply of forage for 40-70% of each 24-hour period....It is also known that horses can experience gastrointestinal discomfort if deprived of food for a mere one to two hours.” 

Gastric Acid Build Up - The Math

  • The average 1,000 pound horse produces 16 gallons of gastric/hydrochloric acid daily.
  • The stomach only has a 2 to 4 gallon capacity.
  • The stomach can empty in 20 minutes - 2 hours depending on the type of feed and rate of consumption. The faster feedstuff is consumed, the less time it spends in the stomach hindering the initial stages of the digestion process - thereby passing quickly and only partially digested to the hindgut. The result of large meals consumed in short periods of time.
  • The math results: 16 gallons divided by 24 hours = .66 gallons produced per hour
  • See more: Equine Gastric Acid - 12 Facts You May Not Know

If we assume the stomach empties in 1 hour - with a 3 gallon capacity - the gastric acid can reach the upper half of the stomach (1 1/2 gallons) in a little over 2 hours.

In addition, the pH of the acid is not being reduced by saliva (rich in bicarbonate) because 1) the horse is without forage, and 2) without chewing, there is no saliva production. Due to this fact alone, equines were not designed to be deprived of forage long enough for the gastric acid to reach the unprotected upper portion of the stomach, if stationary.

Movement (without Adequate Fiber) Doubles the Equation

Movement can cause splashing of acid (learn more about why you need to be careful exercising your horse on an empty stomach), which effectively bathes the upper portion - unless it has fiber creating a protective mat of sorts combined with the reduction of pH from saliva . If the stomach lacks fiber, acid can splash the upper region regardless of how long it's been empty.

What Ulcers Look Like

How to Prevent Gastric Ulcers

Minimize stressful situations, which can include:

  • Lack of forage
  • Confinement
  • Lack of  movement
  • Lack of direct physical interaction with other herd members/isolation
  • Pain
  • Lack of nutrients, vitamins and minerals necessary for proper thyroid, hormone and neurological function
  • Rigorous training
  • Travel

Closing Thoughts

If you suspect your horse has ulcers, consult your veterinarian. Prevention is key. Unfortunately, ulcers have the potential to develop in just 24 hours. 

Helpful How to Resources for Happier Healthier Horses


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Monique Warren, Hay Pillow Founder with the Hay Pillow Slow Feeder product line - standard ground hay pillow, mini hay pillow, hanging hay pillow & horse trailer manger hay pillow

About the Author

Monique Warren invented the Hay Pillow® slow feeder and is the owner of Hay Pillow Inc. ​Warren has been an equine guardian for over forty years and slow-feed advocate for over 10 years. She contributes equine nutrition, digestive and hoof health articles to publications such as Equine Wellness, The Journal, The Naturally Healthy Horse, Natural Horse Magazine, Nicker News, The Horse's Hoof and Miniature Horse World Magazine. Equine nutrition and horses feet are her passions. She resides in Southern California.

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