Iron in the Equine Diet

Many equine mineral supplements utilize dicalcium phosphate (DCP, often referred to as “Dical”), as both a calcium source and a phosphorous source. Along with calcium and phosphorous, DCP carries about 1000 mg/kg (parts per million or ppm) of iron as an inherent part of the rock it came from. Manufacturers often call this iron “background noise” as it is present but was never part of the formulation of the mineral supplement. Most equine supplement manufacturers include this iron on the product tag as part of total iron. If you are trying to source a low iron mineral, the “background noise,” iron might be a source of alarm; however, there is no research that demonstrates that the iron present as a contaminant in dicalcium phosphate is at all available to horses.

There are mineral products available that have been formulated to be VERY low in total iron. These supplements will be using a phosphorous source other than DCP. Be sure to check the tag of any products claiming to be very low in iron, as they may also be low in calcium depending on the phosphorous source used. A low calcium mineral is not necessarily a bad thing for a horse getting calcium from something like alfalfa hay, but if you have a performance horse or, in particular, a growing horse, you should consult with a qualified equine nutritionist or your veterinarian as to whether the mineral is suitable for your horse.

Iron in Water

Water can actually be a more potent source of free iron in your horse’s diet than any feed because frequently the iron in water is in the soluble ferrous (Fe2+) form, as opposed to the more stable ferric (Fe3+) form. Horses can utilize iron in water in the ferrous form much more easily than iron in the ferric form. Water can be a more insidious source of available iron in the equine diet, and should be tested if you have concerns.