There are many reasons horses will eat dirt. Boredom and lack of forage are two examples, but the main reason horses eat dirt is for the minerals.
Minerals are not manufactured in the body, or in the plants that horses eat. There ARE minerals in bodies and plants, but are not manufactured within the system. Minerals come from the soil.
Plants absorb minerals from the soil, but the problem is that the soil varies in mineral content. Different geographical regions have different minerals in the soil, regions vary from too much or to little.
Our horses depend on us to provide them with essential minerals for optimum health. We do this by supplying and providing a good quality concentrate, offering a free choice mineral supplement, or a daily regulated dosage.