Horses eat manure for different reasons depending on their age. For foals, it’s a normal and essential developmental behavior that seeds their gut with bacteria needed to digest fiber. For adult horses, it almost always signals a dietary problem, most often a lack of forage or roughage in their feed.
Foals Need Their Mother’s Manure
Newborn foals are born with a gut that isn’t ready to break down plant fiber. The bacteria responsible for digesting hay and grass don’t appear in a foal’s digestive tract until four to seven days after birth, and they don’t get there on their own. Foals acquire these microbes by eating their dam’s fresh feces, a behavior called coprophagy that begins in the first week of life.
Mare feces serve a dual purpose. They contain live fiber-digesting bacteria that colonize the foal’s intestines, and the feces themselves are roughly 54% fiber, giving those new bacteria something to feed on. Researchers at the University of Florida found an extremely strong correlation (r = 0.97) between the amount of maternal feces a foal consumed and the number of fiber-digesting bacteria established in its gut by day seven. In practical terms, the foals that ate more manure ended up with better-equipped digestive systems.
These fiber-digesting bacteria are strict anaerobes, meaning they die quickly when exposed to air. Fresh manure, still warm from the mare, is one of the only environments where a foal can pick them up alive. This is why foals specifically target their mother’s droppings rather than older piles in the pasture.
Foals typically engage in this behavior from week one through about week 19, with the highest frequency during the first two months. After that, the gut microbiome is sufficiently established and the behavior tapers off naturally. There’s no reason to discourage it. Preventing a foal from accessing its dam’s manure could delay the development of a healthy microbial community and compromise the foal’s ability to extract nutrients from forage later in life.
Adult Horses: A Sign of Dietary Problems
When an adult horse starts eating manure, the cause is almost always nutritional. Horses evolved to graze for 16 to 18 hours a day on fibrous grasses, and their digestive system depends on a steady supply of roughage. When that supply falls short, horses look for fiber wherever they can find it. Stabled horses denied free access to forage will eat their bedding, chew wood, and consume fecal material as substitute sources of fiber.
The pattern is consistent: coprophagy in adult horses shows up predominantly in animals fed concentrate-heavy (grain-heavy) diets rather than fibrous ones. Horses on low-fiber, high-grain rations or protein-deficient diets are the most likely to develop the behavior. Their hindgut bacteria, which produce B vitamins and break down plant material, depend on a continuous flow of fiber to function properly. Without it, the entire digestive ecosystem suffers, and the horse may instinctively seek out fecal material to compensate.
Simply providing adequate hay can reduce or eliminate the behavior. Research on stabled horses has shown that increasing forage access reduces not only coprophagy but also crib-biting, wood chewing, bedding consumption, aggression, and stress. It even improves social behavior among horses housed together.
Parasite Risks From Eating Manure
While coprophagy is harmless and beneficial for young foals eating their own mother’s fresh droppings, any horse that regularly ingests manure faces increased exposure to intestinal parasites. Feces are the primary transmission route for most equine gut parasites, and the risks are real.
Small strongyles (cyathostomins) are among the most common. Their larvae encyst in the intestinal wall and can cause severe inflammation of the colon and cecum when large numbers emerge at once. Chronic cases lead to weight loss and fluid retention from protein loss through the damaged gut lining.
Roundworms (ascarids) are a particular concern for young horses. They can cause small intestinal impactions, and their larval stages migrate through the lungs, potentially triggering bronchitis or pneumonia. Severe cases can lead to intestinal twisting or rupture.
Large strongyles, especially one species called Strongylus vulgaris, damage blood vessels supplying the intestines. This can cut off blood flow to sections of the gut, causing colic and, in serious cases, peritonitis. Tapeworms attach to the junction between the small and large intestine, where large numbers create ulcers and can trigger spasmodic colic or intestinal blockages. Even pinworms, though less dangerous internally, cause intense itching around the tail that leads to hair loss from rubbing.
For adult horses eating manure due to dietary deficiency, the parasite exposure compounds an already unhealthy situation. Correcting the underlying diet problem eliminates both the behavior and the added parasite risk.
How to Stop the Behavior in Adults
The fix is straightforward in most cases: increase the amount of forage in the horse’s diet. Horses should have access to hay or pasture for the majority of the day. If your horse is stalled and receiving most of its calories from grain or pelleted feed, shifting the ratio toward more long-stem hay will usually resolve the problem within days to weeks.
If you’re already providing plenty of hay and the behavior persists, consider whether the diet is adequate in protein. Horses on very mature, stemmy hay or poor-quality pasture may not be getting enough protein even if fiber intake is sufficient. A forage analysis can reveal whether the hay meets your horse’s nutritional needs, and a higher-protein hay or a small protein supplement can fill the gap.
Keeping stalls and paddocks clean by removing manure regularly also reduces opportunity, but it treats the symptom rather than the cause. A horse that’s motivated to eat feces will find a way if the dietary need isn’t met. Focus on the diet first, and the behavior will typically resolve on its own.