Iron (Fe) is found in haemoglobin, myoglobin, cytochromes, and many enzyme systems. Iron plays a critical role in oxygen transport and cellular respiration.
In the body of the horse we find about 70 mg iron per kg body weight. This means that a horse (500 kg) contains about 33 grams of iron. 66% is found in haemoglobin, 20% in myoglobin, 20% in transferrin (transport form), ferritin and hemosiderin (storage form). 0.2% is found in enzymes.
Forage and by-product ingredients commonly contain 100-250 mg Fe/kg dry matter. Grains usually contain less than 100 mg/kg dry matter. Dietary iron absorption in the horse is likely to be 15 per cent or less. Iron utilization increases in iron-deficient rations and diminishes with higher than normal intakes of cadmium, cobalt, copper, manganese and zinc.
The daily requirement for iron is about 40-50 mg/kg dry matter in ration. The requirement for iron should be met under normal feeding conditions.