Geophagia - Why Horses Eat Dirt (And When It Matters)
- May 29
- 3 min read
Some horses nibble at the ground casually as they graze hay, and for many owners it’s one of those behaviours that sits in the “odd but harmless” category. The truth is that dirt‑eating is usually a perfectly normal part of equine behaviour, but it can also be a quiet signal that something in the diet or environment needs attention. Horses are remarkably intuitive about their own bodies, and soil is full of minerals, salts, and trace elements that they instinctively seek out when their diet isn’t quite meeting their needs. A horse that’s a little low in sodium or short on key minerals will often turn to the ground as a natural supplement long before they show any obvious deficiency on the outside.
"Pica" is the general term for a horse eating non‑food items, while geophagia refers specifically to the consumption of soil, sand, or clay, and coprophagia describes the eating of manure. It's very common for foals to eat their dam's manure as a method of populating their gut with flora. Geophagia and coprophagia are therefore subtypes of pica, each pointing to different underlying motivations such as mineral imbalance, boredom, restricted forage, or digestive discomfort.
Geopahgia (dirt‑eating) can also be a form of self‑soothing for the gut. Clay‑rich soils bind acids and irritants, offering a mild antacid effect that feels good to a horse with low‑grade hindgut discomfort. In other cases, the behaviour is simply environmental. Horses on restricted forage, dry lots, or sparse paddocks often spend time nosing through the soil looking for leftover stems or roots, and in the process they ingest small amounts of dirt. Boredom plays a role too; a horse with limited movement or limited forage access will often develop little habits that fill the gaps in their day, and dirt‑nibbling is one of them.
Geophagia/Pica studies
A controlled European study measured soil ingestion in grazing horses by tracking acid‑insoluble ash in their manure. Horses consumed 543–648 g of soil per day, depending on how short the pasture was. Horses grazing closer to the ground ingested more soil. The researchers concluded that pasture height and forage availability strongly influence soil intake.
Several studies and reviews on pica in horses show that dirt‑eating is frequently associated with trace mineral imbalances, especially iron and copper deficiency, and sometimes sodium deficiency.
One study found that soil patches horses repeatedly ate contained significantly higher iron and copper than surrounding soil, suggesting horses were selectively targeting mineral‑rich areas. Horses with pica also had lower serum iron and copper and a lower copper‑to‑zinc ratio than controls.
Feral horses often eat dirt because they’re targeting naturally salty patches to meet their sodium needs. Domestic horses are less likely to become sodium‑deficient if they have access to salt, but if the block is hard to reach, unappealing, or simply not used often enough, that same salt‑seeking instinct can still show up as dirt‑eating.
Where it becomes important to pay attention is when the behaviour is excessive, when the horse is losing weight, or when the soil itself poses a risk.
Persistent pica is associated with increased risk of sand accumulation, impaction, and colic.
Horses that are hungry, under‑mineralised, or stressed may eat more dirt than their system can comfortably handle. If you’re seeing a lot of soil consumption, it’s worth stepping back and looking at the bigger picture: is the horse getting enough forage, enough salt, enough trace minerals, and enough movement? Most horses stop eating dirt once their nutritional needs are met and their environment supports natural grazing behaviour.
As with most things in horse care, the behaviour itself isn’t the problem - it’s the message behind it. Dirt‑eating is one of the small, subtle ways horses tell us what they need. When we listen early, we prevent the bigger issues later.
Sound Advice Mixes to Address Geophagia
Start by ensuring you are meeting their trace mineral needs.
We have three trace mixes that supply optimal copper, zinc, iodine, and selenium, which are commonly deficient in forage. Also, adding around 30g of loose Himalayan salt in feed, and then offering a Himalayan salt block means they can self-supplement. If your pastures are high in oxalates and you are not supplying enough of a high calcium feed like beet pulp or lucerne, calcium might be the culprit.
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