Many people mistakenly believe horses have multiple stomachs. Unlike ruminants, horses have only one. This article explains their unique digestive system and its function, which is fundamental to their care.
A Single Stomach
Horses are classified as monogastric animals, meaning they have a single stomach. This organ is relatively small, typically holding 2 to 4 gallons. The horse’s stomach is C-shaped and designed for a continuous, rather than large and infrequent, intake of food. Its primary role involves the initial breakdown of food through the secretion of hydrochloric acid and enzymes like pepsin, which begin protein digestion. This acidic environment also helps to eliminate harmful bacteria ingested with food.
The Horse’s Unique Digestive Journey
The misconception of multiple stomachs often stems from the horse’s highly specialized hindgut fermentation. After passing through the stomach, partially digested food moves rapidly into the small intestine, which is long and holds a significant volume. Here, most digestible carbohydrates, proteins, and fats are broken down by enzymes and absorbed into the bloodstream. This enzymatic digestion in the foregut (stomach and small intestine) is a quick process, with food moving through the small intestine in as little as 45 minutes to a few hours.
The material then enters the hindgut, which consists of the cecum, large colon, and small colon, making up the largest portion of the horse’s digestive tract. The cecum, a large, comma-shaped fermentation vat, is where the bulk of fibrous plant material is broken down by billions of specialized microorganisms, including bacteria and protozoa. These microbes ferment structural carbohydrates like cellulose and hemicellulose, producing volatile fatty acids (VFAs) that serve as a primary energy source for the horse. This extensive microbial digestion allows horses to extract significant nutrients from forage.
Feeding and Care Considerations
The horse’s single, small stomach and hindgut fermentation system necessitate specific feeding practices. Horses are natural continuous grazers, best suited for a steady, small intake of fibrous forage throughout the day. This constant flow of food and saliva helps buffer stomach acid, produced continuously even when the horse is not eating. Providing consistent access to forage, such as hay or pasture, helps prevent digestive issues.
Feeding large, infrequent meals, especially those high in starches or concentrates, can overwhelm the small stomach and foregut, leading to undigested material reaching the hindgut. This can disrupt the delicate balance of the microbial population, potentially leading to digestive disturbances like colic or gastric ulcers. Gastric ulcers, common in the stomach’s less protected upper region, are linked to prolonged periods without food. Therefore, mimicking natural grazing patterns with frequent, small meals rich in fiber is important for supporting the horse’s unique digestive anatomy and overall well-being.