Horses eat dirt most commonly because they’re seeking minerals their diet is lacking, especially iron and copper. It can also be a response to boredom, insufficient forage, or simply individual preference. The behavior has a formal name, geophagia, and while it’s not always a sign of trouble, persistent dirt eating deserves attention because of the risk of sand buildup in the gut.
Mineral Deficiencies Are the Leading Cause
When researchers analyzed soil from spots where horses repeatedly ate dirt, they found significantly higher concentrations of iron and copper compared to nearby control samples. The horses weren’t eating just any dirt. They were targeting mineral-rich patches, suggesting these specific elements drive the behavior.
Blood work supports this pattern. A study comparing horses with pica (the urge to eat non-food substances) to healthy controls found that horses engaging in the behavior had notably lower serum iron and copper levels, along with a lower copper-to-zinc ratio. Hemoglobin values trended lower too, though the difference wasn’t statistically significant. The takeaway: iron and copper deficiency appears to play a real role in why some horses seek out soil.
Feral horses that eat dirt are often targeting highly saline (salty) spots to meet their sodium needs. Domesticated horses with access to a salt block are less likely to be sodium-deficient, but if the block is inconveniently placed or the horse doesn’t use it regularly, salt-seeking behavior can still show up as dirt eating.
Boredom and Lack of Forage
Not every dirt-eating horse is mineral deficient. Some are just bored. A horse licking its concrete waterer or scooping up a mouthful of soil may be more under-stimulated than nutritionally deprived. Extended periods of confinement with little or no long-stemmed forage are a well-known setup for these kinds of oral behaviors, including wood chewing, mane and tail chewing in young horses, and eating dirt.
Horses have a deep-seated need to chew. When they’re fed primarily pellets or grain concentrates without enough hay, that chewing drive doesn’t get satisfied. The mouth stays busy looking for something else, and dirt is available. Increasing turnout time, providing free-choice hay, or using slow feeders can significantly reduce the behavior in horses where boredom is the root cause.
Some Horses Simply Prefer It
Geophagia appears to be partly an individual quirk. Even horses on well-balanced commercial feeds sometimes eat dirt, and adding extra minerals doesn’t always stop it. Kentucky Equine Research notes that if you’re already feeding the recommended amount of a fortified commercial product, your horse likely isn’t suffering a mineral deficiency, and supplementing more minerals may not resolve the issue. Some horses genuinely seem to like the taste or texture of certain soils, particularly those with a metallic (iron-rich) flavor.
The Real Risk: Sand Buildup in the Gut
The biggest concern with chronic dirt eating isn’t the behavior itself. It’s what accumulates inside. Horses can ingest significant amounts of sand and grit along with soil, and that material settles in the large colon over time. The tricky part is that horses can carry a substantial sand load with no visible symptoms at all.
When problems do develop, the most common presentation is acute colic. This happens when accumulated sand causes a partial or complete obstruction in the large colon, sometimes combined with gas distension behind the blockage. The signs can be vague and overlap with other digestive issues, making it hard to distinguish from other types of colic without a veterinary exam. In some cases, a vet can feel the impaction during a rectal examination or find sand in retrieved fecal samples.
You can do a rough check at home by placing a few fecal balls in a clear plastic bag or glove, adding water, mixing it up, and letting it settle. Sand will sink to the bottom. If you see a noticeable layer, your horse is ingesting more than a trivial amount.
What You Can Do About It
Start by evaluating the basics. Is your horse getting free-choice hay or enough long-stemmed forage throughout the day? Is a salt block available and in a location the horse actually uses? These two adjustments alone resolve many cases.
If the behavior persists despite adequate forage and salt, a blood panel checking iron, copper, and zinc levels can help identify whether a true mineral deficiency is at play. This is worth pursuing especially if the horse is on pasture-only feeding without a fortified concentrate, since pasture mineral content varies widely by region and soil type.
For horses that eat dirt regardless of diet changes, managing the environment becomes the priority. Feeding hay off rubber mats instead of bare ground reduces incidental sand intake. Increasing turnout and social time addresses boredom. Psyllium husk supplements, given in periodic courses, are commonly used to help move accumulated sand through the digestive tract, though their effectiveness varies and they work best as prevention rather than treatment for an existing impaction.
Persistent, aggressive dirt eating that doesn’t respond to dietary or environmental changes warrants a full veterinary workup to rule out underlying gastrointestinal discomfort, including gastric ulcers, which are common in stalled horses and can drive unusual oral behaviors.