Iron deficiency is not the reason your horse is eating dirt.
Question: I live in Arizona and our soil is quite alkaline. The equi based grass formula used to have iron in it, and now it does not, I feed this to both my horses in addition to timothy and Bermuda hay grown in Arizona. One horse is a 15 year old gelding and one 8 year old mare. She eats a lot of dirt, the gelding not so much. If I add iron to their feed they stop eating dirt. What is the best source of iron for them? I have added Red Cell currently with added but it also has other minerals they are already getting in the Equi base grass formula.
Dr. Kellon: Despite your alkaline soils, which do limit iron uptake by the plants compared to acidic soils, there are no cases of diet related iron DEFICIENCY in horses on any soil or hay type. You can check your horses' iron status by sending blood to Kansas State's Comparative Hematology Laboratory, the only lab in the world that can do this testing.