Iron is a trace mineral that is essential in a horse's diet, but iron supplementation is rarely needed. Iron is usually abundant in a horse's diet, yet many horse owners either intentionally or unintentionally give even more iron to their horse in the form of supplements. It is probably safe to say that iron is one of the most over-supplemented trace minerals fed to horses.
Iron Abundance
Iron is in nearly everything that a horse eats and drinks – hay, grass, water, most commercial feeds, and many supplements. Even dirt is an important source of iron. Only 40 ppm of iron is needed in a horse's overall diet daily, but most horse's diets contain much more iron than that. Iron deficiency is very rare, but if a deficiency is suspected in a horse, a serum iron test should be performed by a vet, and iron binding capacity and ferritin levels should also be checked.
Iron, Copper, and Zinc
Excess iron in a horse's diet can block the absorption of copper and zinc, two other trace minerals that are crucial for tendon, ligament, hoof, and skin health. A horse that has iron overload will often have a dull, dry coat, poor hooves, and possible tendon/ ligament problems. While iron is often over-supplemented, copper and zinc are usually under-supplemented. Most commercially- available horse supplements are plentiful in iron, but don't even come close to the National Research Council (NRC) recommendations for copper and zinc.
Anemia and Iron
Anemia is a condition in which there is a shortage of hemoglobin – a protein that transports oxygen from the lungs to the blood. When many people think of anemia, they think of iron as well, but anemia in horses and people differ quite a bit. Iron deficiency anemia does not occur in horses unless there is an extreme loss of blood. Even then, the horse can usually recover in a matter of weeks because its body is so efficient at storing and reusing iron. Excess iron is stored in the horse's spleen, liver, and bone marrow. Supplemental iron is usually not needed in equine anemia as iron does not increase red blood cell counts or hemoglobin.
Effects of Excess Iron
Too much iron in a horse's diet has many effects including:
- Predisposition to infection
- Secondary zinc and possibly copper deficiency
- Predisposition to arthritis
- Increased tendon/ ligament problems
- Predisposition to insulin resistance
- Liver disease
Iron Overload and Death
Too much iron in a horse's system can lead to liver damage and even death. Foals are especially susceptible to iron poisoning, but it is not unheard of in adult horses either. According to Dr. Kellon VMD, equine nutrition expert, "As little as 350 mg (common level in a dose of blood builder supplement) of supplemental iron can kill a foal."
Iron should never be supplemented unless an iron deficiency has been diagnosed by a veterinarian. Many horse owners unintentionally feed extra iron to their horses in commercial feeds and supplements. Always look at the specific ingredients in any feed or supplement you give your horse, and try to avoid those with high iron amounts if you can.
Sources:
- Kellon, Eleanor V.M.D. "The Trace Minerals." NRC-Plus. 2008.
- "Why Extra Iron is Bad for your Horse." The Horse Journal.
- Kellon, Eleanor V.M.D. Horse Journal: Guide to Equine Supplements and Nutraceuticals. Guilford, CT: The Lyons Press; 2008.
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