Iron in the Equine Diet

Once the iron absorbed from the small intestine is actually in the bloodstream, it is transported by a protein called transferrin to the liver and spleen for production of hemoglobin, myoglobin, or a storage form of iron called ferritin. Ferritin, stored in the liver and spleen, keeps extra iron not immediately needed by the horse in a safe non-reactive form, so it is available for use by the horse when needed.  Excessive free iron Fe2+ in the circulatory system of the horse will cause oxidative stress and tissue damage consistent with what is called iron overload, but fortunately, the equine metabolism is well-equipped to ensure that this rarely ever happens.

Facts About Iron and Horses

There is plenty of misinformation on the internet about the effects of excessive iron in equine diets. Always look for peer reviewed research if you are in any doubt about anything you read online. The reality is that horses do need iron in their diets. According to the National Research Council (NRC) 2007 Nutrient Requirements of Horses, mature horses require a daily intake of 40 mg of available iron per kg of dry matter intake. That means a mature 500 kg horse eating 2 percent of his body weight in dry matter will eat 10 kg of dry matter per day, thus 40 mg/kg x 10 kg = 400 mg of available iron is necessary daily for normal metabolism in our horse. As the workload of a horse goes up, the dry matter intake also increases, as does the requirement for available iron. NRC has established that growing foals and pregnant or lactating mares need 50 mg/kg of dry matter intake. Your horse’s diet probably provides iron in excess of that, but it has been well-established in research that not all of that iron is available to horses, and in addition to this, horses have an excellent ability to regulate the uptake of iron in the gut. The more iron in the diet, the less they actually absorb. Research in horses has established that on average only 20 percent of the iron they consume is actually available. A great deal of the iron they consume is not digestible and will be excreted in the manure

Main Sources of Iron in the Horse’s Diet

The typical equine diet will provide at least 100 mg of iron per kg of dry matter daily. That means that our 500 kg horse eating 2 percent of its body weight in dry food per day (10 kg) will consume at least 100 mg x 10 kg = 1,000 mg of iron per day. In many