Why Is He Eating THAT?- Unusual Eating Behaviors in Horses

Karen E. Davison, Ph.D.
Manager-Equine Technical Services
Land O’Lakes Purina Feed






Horses are expected to eat grass, hay, grain, maybe treats like carrots or apples. They aren’t expected to eat dirt or manure, but sometimes they do. Both behaviors are offensive and worrisome to horse owners, but are they really harmful to the horse? The term “pica” refers to persistent eating of non-nutritive substances for at least one month’s time. This activity exists in many animals, including humans, and is most common in younger animals. It has been reported that 10 – 32% of children between 1 – 6 years of age engage in pica. In some cases, specific nutritional deficiencies may trigger unusual cravings, such as a long-term phosphorus deficiency causing herds of cattle to eat bones or significant amounts of dirt. However, in horses these behaviors are not defined as stereotypic stable vices because they appear to represent a normal physiological or foraging response.

Unusual oral behaviors in horses include coprophagy and geophagia. Coprophagy, eating manure, is normal in young horses from 5 days to 2 months of age. Foals typically eat their mothers’ manure but occasionally consume their own or an unrelated adult’s feces.This practice is more common in foals confined to stalls than those on pasture, and is uncommon after 6 months of age. The purpose of coprophagy in foals has been speculated to be a mechanism for populating the digestive system with bacteria and protozoa necessary for a fully functioning cecum. These microbes are required for effective fiber digestion, which is necessary for a foal to fully utilize a grass or hay diet as it grows and consumes more forage and less mare’s milk.

There has been no nutritive motivation identified for coprophagy in foals, but mature horses eating protein deficient diets will often begin eating their manure. In these cases,coprophagy ceases when adequate protein is provided. Horses in starvation situations or those without adequate hay or pasture (consuming less than 1.3 lbs of hay per 100 lbs of body weight) have also been found to eat manure. There are reported cases of coprophagy in horses older than 6 months of age consuming diets that are very adequate in protein, fiber and provide a complete balance of vitamins and minerals. These reports appear to be more common in the springtime, with stabled horses, and more often in young stallions. Boredom may be the reason coprophagy appears more in confined horses than pastured horses. Parasite infestation would be a primary concern in these animals, so routine cleaning of facilities and a good deworming program would be important.

Geophagia refers to eating dirt and is reported to be fairly common in feral horses. Geophagia is not simply horses taking in dirt while grazing close to the ground or eating grain off the ground, but is a behavior where horses actively bite into the ground to specifically eat dirt. Dirt-eating has been proposed to be a search for salt or minerals, but analysis of soils shows no consistent mineral profile of consumed versus non-consumed soils. The soils tested varied tremendously in mineral content. Domestic horses consuming diets providing plenty of salt and mineral have also been seen consuming dirt.So, geophagia is probably not simply a pursuit of minerals. Anecdotal evidence indicates dirt-eating may be more common in stallions than mares or geldings, but no studies of gender effects on geophagia have been reported. Although geophagia is generally harmless, consumption of sandy soil can cause colic or diarrhea. Some horses are more prone to eating sand than others, even when eating the same diet under the same conditions. Grazing sparse pastures on sandy soil, horses that are thinner and younger,and feeding grain on the ground are all factors that contribute to increased ingestion of sand.

If individual horses are observed exhibiting unusual eating behaviors such as coprophagy or geophagia, horse owners should evaluate the nutritional balance of the diet, the availability of ample roughage, and the general environment for potential causes of the behavior. A veterinary exam to detect parasite infestation or other health issues may also be warranted. If the diet is adequate, the horse is healthy and other factors are not at play,then it may be a simple case of boredom. Decreasing time spent in confinement,providing a companion and increasing exercise may help alleviate the problem.