Some horses will paw and dig up clay and soil and eat it on a regular basis. Accidental ingestion of sand is common in horses grazing short pastures on sandy soils, particularly during drought conditions, or when confined to dry lots or sandy corrals with hay fed on the ground. Build up of sand in the narrow segments at the bends of the large bowel inevitably leads to sand impaction, colic and fatal bowel rupture.
This habit is primarily boredom related, but lack of iron, copper, calcium and phosphates in the diet is claimed to trigger the desire to eat dirt. Gastroduodenal ulceration resulting from highly concentrated or refined diets has also been suggested.
In sandy areas where grazing increases uptake of sand, heavy burdens of hypobiotic or encasted Cyathostome spp. (Small Redworms) in the colon wall is considered to increase the prevalence of sand colic, as bowel movement may be reduced. Different sand types may be more likely to cause accumulation than others, with fine sand the most dangerous.
In sandy areas, horses should be shifted to longer pastures on a regular basis, or provided ad-lib hand feed and hay in hay stacks. Regular bimonthly drenching with laxative gels may be suggested by your vet. Stabled horses that eat sand whilst in their outside corrals should be provided with hay in a hay rack located on a compact area. Mixing of 3oz psyllium husk into the feed once weekly, or giving 1oz of Epsom salts is helpful in preventing sand accumulation in the large bowel.
When a horse develops a craving for sand or dirt, provisions of a daily vitamin/mineral supplement, and a calcium supplement may help control the habit. Alternatively, mixing half a cup of powdered red clay into the night feed may be worth trying, as is a dose of sulphur powder (2 teaspoons daily) or meat meal.
A full examination by your veterinarian should be carried out on horses, as mouth lesions and gastric ulceration may cause them to habitually seek out and eat clay or soil. Mixing 1 1/2oz or three tablespoonfuls of bicarbonate of soda into the evening meal is widely regarded by horse owners as a useful therapy to reduce an uncomfortable stomach burning sensation in horses on high grain diets.