When formulating a feed strategy for your horse, it is important to remember that these large mammals are herbivores. Meaning, over the millions of years that horses have evolved, their digestive tracts are specialized for a grazing diet.

Grazing animals are meant to eat grass and other plants consistently throughout the day. Thus, their digestive tracts are specialized to match this behavior. It is also critical to understand a horse’s digestive biology to develop a proper feeding strategy to prevent ulcers and other dangerous conditions such as colic.

First and foremost, horses should always have access to free-choice water throughout the day. If using buckets or large containers for water, they should be checked periodically throughout the day and filled if needed. Automatic waterers should be checked daily to ensure they are functioning properly. On average, an adult horse can consume 10 gallons (38 liters) of water per day.

The horse’s digestive system can best be thought of as an assembly line. Unlike carnivores, who often will eat one large meal a day, horses and other herbivores eat small meals consistently throughout the day. Behavioral studies in wild horses and other equids demonstrated that when left on pasture, equids will graze up to 18 hours a day. In comparison, stalled horses can consume a hay ration within two hours. To slow down consumption of hay, the recommended use of “slow feed” hay nets has increased. On average with these nets, a horse will consume their hay ration over five hours rather than two. Thus, this supports the horse’s natural biology of eating throughout the day.  

An average sized horse (1000 lb) should consume approximately 3% (30 lb) of their body weight per day in feed. Digestion for a horse can take as little as 36 hours in a grain-heavy diet. For a forage-heavy diet, digestion can take longer and up to 72 hours. This allows the time needed to break down the fibrous material and absorb the nutrients in the hind gut. Because the horse’s biology dictates that feed is consistently entering and exiting their digestive tracts, horses can defecate anywhere from four to thirteen times per day.

An adult horse’s stomach is relatively small for its body size and can hold up to 3 gallons (12 liters). Interestingly, food only remains in a horse’s stomach for about 15 to 20 minutes before it is passed into the small intestine. Relatively little digestion takes place here. Also, data has shown that consistent feed into the stomach has been correlated with a lower incidence of ulcer formation.

The small intestine is roughly 70 feet (21 meters) long in a medium-sized horse. This is the major site of digestion and absorption of nutrients. Importantly, this is also where bile is secreted. Bile allows the breakdown and emulsification of fats. Unlike other mammals, horses do not have a gall bladder and cannot store bile. Thus, for horses, bile is consistently secreted into the small intestine. This, again, supports an animal that is meant to eat consistently throughout the day.

The large intestine, primarily the cecum, is where digestion tends to slow in the horse. This is also where the hind gut “ferments” any forage. In a medium-sized horse, the cecum is like a large vat and can hold up to 18 gallons (70 liters) of material. This is also the site of where many types of colic can happen in the horse.

Briefly, colic is a very painful digestive disturbance that can lead to the death of a horse. Impaction colic is one of the most common types. In this type of colic, partially digested feed builds up in the large intestine and becomes “blocked,” stops moving, and results in the impaction. Since the most common feeding practice is to feed horses two meals per day (usually morning and evening), research data has shown the incidence and risk of impaction colic increases.

Taken together, at a bare minimum when feeding concentrate and/or hay, the meals should be weighed, evenly divided out, and fed accordingly. Ideally, the feed should be divided out and fed three or four times daily. The practice of feeding smaller meals more often throughout the day has been correlated with a lower incidence of colic and other digestive disturbances in horses. This also supports the horse’s natural behaviors and digestive biology.

Finally, it is usually never recommended to feed a horse a single meal per day. In some circumstances with very small meals, this may be acceptable. If you have any questions or concerns for your own horse, we encourage you to reach out to us directly to develop a personalized feeding plan tailored for your animal.

 

Chris J. Mortensen, Ph.D.