These supplements are listed as "no iron added." This means that the iron element is not added. This does NOT mean that these supplements are completely iron-free. Iron is contained in many ingredients used to make these supplements. For example, magnesium oxide, a commonly used form to supplement magnesium, contains a small amount of iron from the oxide part. All of these supplements contain a few milligrams of iron.
Listed supplements are designed for mature, non-breeding horses.