Although more commonly seen in foals, adult horses may also intentionally eat soil or dirt. Theories for this behavior include compensation for dietary deficiencies (salt and minerals), ingestion of micro-organisms or clay (digestive aid), or behavioral issues (boredom). It is hard to keep a horse from eating dirt and, generally, it is not necessary.

However, it is important to prevent your horse from ingesting sand in large quantities. Sand can accumulate in the horse's intestines and cause life-threatening intestinal crisis. It is all about the particle size- sand versus dirt.