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ES Insulin dysregulation in horses: a new epidemic or a new perspective?
January 4, 2024
Pica in horses – Part I: geophagia
Sometimes you suddenly see it happen: your horse takes a bite of sand, licks a puddle of mud, or digs with its nose into the ground as if looking for something. Is that normal? Or a reason for concern?
This behavior, which is known as geophagy, falls under a broader disorder that we itchy Pica: the consumption of inedible or non-nutritive materials such as soil, manure, wood, or hair. In this blog series, we dive into the three most common forms of pica in horses: geophagia (Part I), coprophagia (eating manure – Part II), and lignophagia (eating wood – Part III). We support each part with current scientific insights and practical tips for management and nutrition.
Pica is the recurrent eating of non-nutritive or inedible materials. Think of soil, plastic, paper, wood, manure, or small stones. This behavior occurs in all breeds, ages, and housing systems, from wild mustangs to sport horses on full board.
A frequently heard explanation is a nutrient deficiency – especially copper, iron, or salt – but the reality is more nuanced. According to research, horses only recognize three fundamental deficiencies: energy, salt, and water. Even so, some horses appear to instinctively search for certain minerals, although science is not unanimous on this.
Furthermore, research shows that horses do not always make ‘the right choice’ when they want to compensate for deficiencies. Ponies that received too little phosphorus actually consumed more calcium, which further disrupted their mineral balance.1
Although eating earth is often interpreted as deficiency behavior, several other explanations are possible:
There is evidence that a lack of certain trace elements (such as copper or iron) may contribute to geophagy. In one Australian study, a higher copper and iron content in the soil was found in geophagic zones among grazing horses.23
Yet other soil analyses show that there is no consistent mineral pattern in the places where horses eat earth. The explanation is therefore not purely nutritional.
Geophagy also occurs in horses with stomach or intestinal problems. Some researchers suspect that horses eat earth to protect the mucous membrane or to ‘calm’ the digestive tract.4
It is striking that in an Egyptian study, horses with geophagia suffered from colic less often than their peers. Whether this is due to a protective effect or coincidence has not yet been clarified.5
Prolonged box rest, too little roughage, or a boring environment can trigger behaviors such as licking, chewing, and eating soil. Especially young horses and socially subordinate animals exhibit this behavior when their grazing instinct is not sufficiently satisfied.6
Wild horses explore their environment with their noses and lips. They regularly come into contact with soil, humus, and plant debris. Our domesticated horses retain this natural curiosity. Do they eat sand because they are ‘missing something’? Not necessarily. Sometimes it's just... being a horse.
Some horses develop this behavior without a clear medical or nutritional cause. Think of stallions that show more exploratory behavior, or horses with a specific preference for certain soils. It is a form of behavior that sometimes falls outside the classical frameworks.
Ingesting a little sand is normal for grazing horses, but excessive geophagia can have serious consequences:
Sand accumulation in the intestines, with the risk of sand colic and motility disorders7
Bowel obstruction and perforation upon ingestion of gravel, clay, or hard soil particles
Reduced mineral absorption, because sand binds certain nutrients (such as iron)
Increased risk of parasitic infection, especially with soil contaminated with manure2
Pay attention to the following signals:
Repeated licking or eating of soil or sand
Sand or mud around the lips and nose
Particles in the manure
Weight loss or unexplained colic symptoms
Boredom, nervousness or abnormal stable behavior
An effective approach requires a holistic perspective:
Part II – Coprophagia: Why some horses eat manure, and what this means for their health.
Part III – Lignophagy: The urge to eat wood explained.