Risk Factors for Gastric Problems in Horses: What Every Horse Owner Should Know
Horses are more susceptible to gastric problems than most people realize — and the way we manage their diet and environment plays a major role in preventing them.
In this article, we cover the main risk factors for gastric ulcers in horses, including feed management, diet type, stress, intense exercise, NSAID use, and the critical weaning period in foals. We also share science-backed strategies to protect your horse's digestive health — from feeding practices and medications to nutritional support with pre- and probiotics, alfalfa, and beta-glucans.
The equine stomach has several unique characteristics — most notably, its relatively small size and the fact that it continuously secretes gastric acid, even when empty. Maintaining proper gastric balance depends on adequate chewing cycles and efficient digestive tract motility.
This balance is directly influenced by external factors such as diet type, management practices, and environmental conditions (ARANZALES & ALVES, 2023). Given the high incidence of gastric disorders in horses, it is essential to adopt nutritional and environmental management strategies to both treat affected animals and prevent the risk factors associated with these conditions.
1. Anatomy and Physiology: Understanding the Equine Stomach
Horses are monogastric animals classified as non-ruminant herbivores. The stomach is relatively small, representing approximately 9% of the total digestive volume (AL JASSIM & ANDREWS, 2009). It is divided into two main regions: the upper half, which has no glands, and the lower glandular portion, which secretes protective substances to shield that region from injury (BANCE & ANDREWS, 2019) — while gastric acid is continuously produced for digestion.
The small intestine is where chemical digestion and nutrient absorption primarily occur. The large intestine hosts a complex microbial population, playing a critical role in the animal's overall health and in the breakdown of fibrous feed (AL JASSIM & ANDREWS, 2009).
As described by Wolter (1975) and cited by Thomassian (1990), "the digestive physiology of the horse is characterized by intense chewing, rapid gastric transit, a brief but intense enzymatic digestion in the small intestine, and a prolonged microbial action in the large intestinal reservoirs."
2. Gastric Problems in Horses
Horses have a high incidence of gastric conditions such as ulcers and gastritis. Among the most common contributing factors are feed management practices, excessive grain feeding, limited access to roughage, intense exercise, and stressful situations (AL JASSIM & ANDREWS, 2009).
The most prevalent gastric conditions are gastric ulcers, which are classified according to their location in the stomach:
- Equine Squamous Gastric Disease (ESGD): Ulcers located in the squamous (non-glandular) portion of the stomach (BANCE & ANDREWS, 2019). This region has minimal natural defenses, making it more vulnerable to rapid lesion development (HEPBURN, 2011).
- Equine Glandular Gastric Disease (EGGD): Ulcers located in the glandular portion of the stomach (BANCE & ANDREWS, 2019). These develop more slowly, following a breakdown in the protective mucosal barrier mechanisms (HEPBURN, 2011).
3. Risk Factors for Gastric Problems
3.1 Feed Management
The equine stomach has a limited capacity, which restricts the amount of feed that can be consumed at once. When horses consume large volumes in a short period, the stomach cannot digest properly (SANTOS et al., 2012).
Additionally, extended fasting periods increase the exposure of the gastric mucosa to acid, alter the intestinal microbiota, and can significantly compromise digestive health — raising the risk of gastrointestinal problems (COSTA et al., 2020).
The ideal management approach involves offering small amounts of feed multiple times throughout the day, ensuring consistent and balanced feeding to protect the stomach and support healthy digestion.
3.2 Type of Feed
Feeding horses diets rich in non-structural carbohydrates (such as grains and concentrates), especially in large quantities or after prolonged fasting, increases the duration of gastric acid exposure and can potentially lead to ulcer development (AL JASSIM & ANDREWS, 2009).
An important anatomical feature of horses is the tight connection between the esophagus and the stomach, which prevents regurgitation. This means that when large amounts of concentrate are consumed at once, the stomach simply cannot digest them properly (SANTOS et al., 2012).
When roughage is offered before concentrate feed, it stimulates greater salivation — which helps neutralize gastric acid and promotes better flow of stomach contents into the large intestine (MEYER, 1995).
3.3 Stress
Transport, where animals spend extended resting periods in constant motion, along with environmental changes and isolation, are well-recognized risk factors for the development of gastric lesions in horses (RIBEIRO et al., 2019). Stress directly impacts gastric acid secretion and the integrity of the protective mucosal barrier.
3.4 Intense Exercise
High-performance horses are typically fed grain-rich diets twice daily and have their feed withheld for extended periods before exercise. The combination of a high-starch or high-non-structural carbohydrate diet, increased gastric acidity, reduced saliva production, and fasting periods contributes to a cascade of digestive issues — including fermentative acidosis, equine metabolic syndrome, Cushing's disease, laminitis, and colic — in addition to significantly increasing the risk of gastric ulcers in performance horses (AL JASSIM & ANDREWS, 2009).
3.5 Medication Use
The use of non-steroidal anti-inflammatory drugs (NSAIDs) is a common practice in equine veterinary medicine. While recognized for their analgesic and anti-inflammatory properties and widely used to treat various conditions in horses, NSAIDs have a narrow safety margin and can cause gastric irritation and mucosal damage when used without appropriate management support (FLOOD; STEWART, 2022).
3.6 Life Stage: Weaning as a Risk Factor for Gastric Ulcers
The weaning period is recognized as one of the highest-risk phases for the development of gastric ulcers in foals. The combination of physical, nutritional, and social stress during this period — including separation from the mare, the abrupt transition from liquid to solid feed, and adaptation to new environments — elevates cortisol levels, reduces voluntary feed intake, and increases fasting periods. All of these factors increase the exposure of the gastric mucosa, particularly the squamous region, to hydrochloric acid (MURRAY et al., 1987).
Studies show a high prevalence of gastric lesions in post-weaning foals, often subclinical in nature, which can compromise growth, performance, and well-being if appropriate nutritional and environmental management strategies are not implemented (MURRAY et al., 1987).
4. Strategies to Prevent and Manage Gastric Problems
4.1 Improving Feed Management
Continuous feeding keeps the horse's stomach fuller throughout the day, and the constant buffering effect of saliva helps protect the non-glandular region from acid-related injuries. The energy a horse requires is derived from digestible nutrients, including carbohydrates, proteins, and fat (AL JASSIM & ANDREWS, 2009).
Forages provide bulk, energy, protein, minerals, vitamins, and other essential nutrients to sustain horses in maintenance or light work (HUSSEIN; VOGEDES, 2003). When horses are allowed to graze freely on pasture, they spend approximately 18 to 19 hours per day grazing (SANTOS et al., 2012). Dietary fiber plays a fundamental role in equine nutrition, forming the foundation of balanced equine feeding (BRANDI; FURTADO, 2009).
4.2 Medications
The treatment of gastric conditions in horses is primarily based on reducing gastric acidity to allow ulcer healing. Omeprazole is the most widely used and effective medication for this purpose. Histamine H₂ blockers such as ranitidine and cimetidine may also be used, though with lower efficacy (HEPBURN, 2011).
Alongside medication, combining changes in feed and environmental management is essential to prevent recurrence. Antacid supplements may be used as a complementary support measure.
4.3 Diet and Nutritional Support
Dietary strategies for preventing gastric problems in horses include a range of protective nutrients and feed types:
- Alfalfa hay helps reduce gastric acidity due to its high calcium and protein content, providing a protective effect against ulcers.
- Rice bran, which contains gamma-oryzanol, has antioxidant properties and may help reduce gastric acid secretion.
- Pre- and probiotics contribute to intestinal microbiota balance and overall digestive tract health — especially important given that gastric ulcers can alter gut pH and consequently microbiota composition.
- Beta-glucans help protect the gastric mucosa and improve carbohydrate digestion.
- Herbs such as licorice root and rosemary have antacid, anti-inflammatory, and healing properties that support digestive balance (FEITOSA FILHO & MODESTO, 2019; GADELHA et al., 2022).
- Soybean oil and flaxseed oil, through the action of lecithin, may help form a protective barrier in the gastric mucosa against acid damage (ARAMAKI et al., 2020).
5. Preventing Gastric Problems in Horses
Management errors make horses significantly more susceptible to gastric disorders — largely due to the unique anatomical and physiological characteristics of the equine stomach, particularly its sensitivity to diet and stress. Adopting appropriate feed management practices, reducing stressors, and implementing preventive nutritional strategies are all essential to maintaining gastric balance, preventing digestive disorders, and promoting the health and well-being of horses at every stage of life.
References
COSTA, L. M. et al. Experimental crossover study on the effects of withholding feed for 24 h on the equine faecal bacterial microbiota. BMC Veterinary Research, v. 16, p. 234, 2020.
HEPBURN, R. Gastric ulceration in horses. Equine Practice, v. 33, n. 3, p. 116–124, 2011.
RIBEIRO, G. et al. Stress and gastric ulcers in transport horses. Journal of Equine Science, 2019.
SANTOS, A. et al. Manejo alimentar de equinos. Revista Brasileira de Medicina Veterinária, 2012.
THOMASSIAN, A. Enfermidades dos Cavalos. 4. ed. São Paulo: Varela, 1990.
Frequently Asked Questions (FAQ)
1. What are the main risk factors for gastric problems in horses?
The main risk factors include improper feeding management, prolonged fasting, excessive grain or concentrate intake, limited access to roughage, intense exercise, stress, transportation, environmental changes, isolation, NSAID use and weaning.
2. Why are horses particularly susceptible to gastric ulcers?
Horses have a relatively small stomach and continuously produce gastric acid, even when the stomach is empty. The upper, non-glandular portion of the stomach also has limited natural protection against acid-related injury, making it more vulnerable to ulcer development.
3. What is the difference between ESGD and EGGD in horses?
Equine Squamous Gastric Disease, or ESGD, affects the squamous, non-glandular portion of the stomach. Equine Glandular Gastric Disease, or EGGD, affects the glandular portion. ESGD can develop rapidly because the squamous region has minimal natural defenses, while EGGD develops following a breakdown in the glandular mucosa’s protective mechanisms.
4. How does prolonged fasting affect a horse’s gastric health?
Prolonged fasting increases the exposure of the gastric mucosa to acid. It can also alter the intestinal microbiota and compromise digestive health, increasing the risk of gastrointestinal problems.
5. Why should roughage be offered before concentrate feed?
Offering roughage before concentrate stimulates greater saliva production. Saliva helps neutralize gastric acid and supports the movement of stomach contents through the digestive tract.
6. Can stress contribute to gastric ulcers in horses?
Yes. Transportation, environmental changes and isolation are recognized risk factors for gastric lesions. Stress can affect gastric acid secretion and compromise the integrity of the stomach’s protective mucosal barrier.
7. Why are performance horses at greater risk of gastric problems?
Performance horses are often fed grain-rich diets and may have feed withheld for extended periods before exercise. High-starch diets, increased gastric acidity, reduced saliva production and fasting can significantly increase the risk of gastric ulcers and other digestive disorders.
8. Can NSAIDs cause gastric problems in horses?
Yes. Non-steroidal anti-inflammatory drugs have a narrow safety margin and may cause gastric irritation and damage to the stomach lining when used without appropriate management support.
9. Why is weaning a risk factor for gastric ulcers in foals?
Weaning combines physical, nutritional and social stress. Separation from the mare, the transition from liquid to solid feed and adaptation to a new environment can increase cortisol levels, reduce feed intake and prolong fasting periods. These changes increase the exposure of the gastric mucosa to hydrochloric acid.
10. How can gastric problems in horses be prevented and managed?
Prevention and management involve offering small amounts of feed several times throughout the day, maintaining consistent access to forage, reducing prolonged fasting, limiting stress and adopting appropriate nutritional strategies. Alfalfa hay, rice bran, prebiotics, probiotics, beta-glucans, certain herbs and soybean or flaxseed oil may provide additional digestive support. When gastric ulcers are present, treatment may include acid-reducing medication such as omeprazole, together with changes in feeding and environmental management.
