Be Cautious With Iron

Iron is essential for all forms of life; a mineral element that has no substitute and powers key life-sustaining reactions in your horse’s body.  Iron also has an insidious dark side.

From pregnancy to performance, nothing happens without iron

The most well know role of iron is in red blood cells, where iron forms the active center of hemoglobin, the pigment which carries oxygen in the red cells. It performs a similar function in the muscle pigment myoglobin, which gives muscle its red color. Iron is needed for thyroid hormone production. Iron containing enzymes are also used inside the cell’s nuclear powerhouses, the mitochondria.

Iron has many functions because chemically it is extremely reactive – almost too reactive. Unfettered iron is like molecules in a nuclear reactor. It can do a tremendous amount of damage to the tissues. In a normal horse, there is virtually no free iron. It is all securely bound to carrier and storage proteins until well controlled and sequestered reactions free it up for use.

Because of the important jobs iron performs, and the fact deficiency is common in humans, iron finds its way into  equine vitamin and mineral supplements and fortified feeds. Iron is a common ingredient in “blood builders” and widely recommended for any horse that is anemic.

However, more is not better for iron and the truth is that equine diets contain more than enough (sometimes much more) iron than the horse needs.  There has never  been a documented case of iron deficiency anemia in an adult horse – ever.  Still, since it’s so important it can’t hurt to supplement anyway, just in case – right? Actually, no.

Because free iron is so dangerous to the body, there is an intricate system to keep it under control. Iron can be absorbed through the gaps between intestinal cells, a process that is increased in the presence of products of fermentation of hay/forage. Otherwise, iron is absorbed into intestinal lining cells in the small intestine. From there, its release into the body is controlled by hormones/regulators that can block movement out of the cell and control the electrical charge of the iron, which in turn determines if it can be picked up by its carrier protein, transferrin.

Once iron is in the body, it is basically there to stay. Unlike other minerals, the body has no avenue  for getting rid of iron other than tiny amounts in sweat. This iron accumulates over time. A high enough dose all at once can kill a horse (foals are especially susceptible) but toxicity is more likely to build up over time.

In 2019, Theelen et al published a paper documenting iron overload and liver damage in horses consuming natural water sources with iron contents of 0.72 to 75.2 ppm at the time of testing. . Kellon and Gustafson 2020 described abnormal iron indices in two populations of horses with high insulin levels –  an association that is well established in people, multiple other species of animals and even birds.  Less dire consequences may include anemia, muscle pain, copper and zinc deficiency, poor performance and poor coats from the oxidative stress.

Even unsupplemented diets often contain considerably more iron than the horse needs and levels in the body will rise over time. It makes no sense to add to the burden with the horse’s supplements. Look for the words iron and ferrous in both the analysis and the ingredients list.

Eleanor Kellon, VMD



About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions,, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition .
This entry was posted in Equine Nutrition and tagged , , , , , , , , . Bookmark the permalink.

6 Responses to Be Cautious With Iron

  1. Sally says:

    Dear Dr. Kellon, I am wondering if there is a high amount of iron found in hemp products for horses. I would appreciate your superb knowledge input on this question. Thank you so much.


    • Dr. Kellon says:

      Hemp seed oil has no iron. The cannabinoid extracts are not fed in large enough amounts to worry about the iron. Hemp seeds have been analyzed to contain 140 ppm iron with less than 10 ppm copper, zinc, manganese . Depending on where and how it was produced, hemp seed meal (a protein source) could be much higher in iron from the processing equipment.


  2. Dr. Kellon says:

    You would have to speak with a water treatment company regarding your options – e.g. there are filters that can be used on hoses.


  3. Jonna Kelner says:

    Hello, found your blog via Pete Rameys site . I recently discovered that some of the issues I am fighting with my horses skin ( scratches that have been very difficult to manage) might have to do with too much Iron throwing off his Copper /Zinc ratio. I have started changing his diet to lessen Iron but we live in an area that has high iron in the water. Filtering water is not a reasonable management option for us. What are other recommendations you can make?


    • Dr. Kellon says:

      The best thing to do is avoid iron fortified feeds or supplements, get your hay and water analyzed then have the diet correctly balanced. In the meantime, use Uckele U Balance Foundation which I formulated specifically for high iron situations


      • Jonna Kelner says:

        Hello Dr Kellon, Thank you for the response. Hoping our hay supplier has the nutrient profile already done so waiting to hear back . Will pursue water testing but I think for the most part we are going to have to work around that as mitigating iron levels of water off of a well head might prove impossible. Do you have any feedback on ways to work around that?


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