Iron In The Horse's Diet: Careful Monitoring Is Needed To Maintain Equine Health And Avoid Common Health Problems

Iron is an essential micromineral in the horse's diet and nature has provided an abundance of it in soils, plants and water.  Deficiencies in this mineral are very rare while excess amounts are all too common and can affect a horse's health in detrimental ways.  If your horse has any immune issues, metabolic conditions, infections, or laminitis pay extra attention to iron levels in the diet.  Here is a breakdown of quick facts you should know about iron (Fe).  [All values are expressed on a Dry Matter Basis (DM);  ppm (mg/kg) refers to concentration in the total diet.]


Iron Importance:  Iron is found in four areas in a horse's body and is an essential component of blood hemoglobin protein (60%) and muscle myoglobin protein (20%);  20% is found in the blood.  Iron is also found in the enzyme systems.


Daily Requirements (NRC):  50 ppm fed for foals (excluding newborns), pregnant and lactating mares, and 40 ppm fed for mature horses. Forages, feeds, grains and supplements will have varying amounts of iron (Fe).  Forages typically have 50-500 ppm  Fe;  Cereal Grains have 20-100 ppm Fe. 


Recommendations:  While most healthy horses have a wide tolerance to iron levels beyond the 40 ppm recommendations (to a maximum of 500 ppm) many horses are sensitive to high levels of iron in their diet.  If the horse is overweight, insulin resistant, has/had laminitis, or PPID (Equine Cushing's Disease), adjust your feeding plan to one that is closer to the NRC daily requirements.  The minimum requirement for a 400 kg horse that is not exercised is just 320 mg iron per day (NRC).


Iron Deficiencies:  Rare in normal, healthy, growing and adult horses; decreased exercise capacity; could lead to anemia.   Deficiencies are most often due to blood loss; likely a secondary problem exists and vet should be consulted.  Foals are born with a high tissue concentration of iron and so do not require supplemental iron/ iron injections especially in the first two weeks of life.


Iron Supplementation:  No known benefits for non-anemic horses.  Iron injections should not be given to horses unless tested and advised by a veterinarian; injections can cause severe reactions or death. Iron, as in all minerals, needs to be balanced in the diet with other minerals such as Copper, Zinc and Manganese to maintain good health. 


Excess Iron:  Maximum tolerable concentration is 500 ppm of feed per day (NRC).  Excess iron is problematic: decreases disease resistance and immunity, decreased athletic performance, iron accumulation in organs leading to liver failure; iron is considered an antagonist - causes interference with the absorption of other minerals ie copper, zinc and manganese, leading to other health issues; depression, dehydration, diarrhea, insulin resistance (and laminitis), and increased risk of bacterial infections.  Supplemental iron can be toxic to foals.


A Typical Feed Program If you have a 500 kg working horse (1270 lbs) it requires a minimum of 500 mg of iron per day (NRC).  A typical diet (hay, commercial feed, oats) may have a total of 3,053 mg of Iron in the diet with an iron concentration of 260 ppm. 


To maintain good health for your horse, always analyze the hay and balance the nutrients in your horse's diet.  Feed My Horse Equine Nutrition Software makes it easy to monitor iron levels in your horse's diet to keep your horse healthy!


[The complete version of this article will be posted in an upcoming blog at].





Jean Klosowicz

Equine Nutrition Consultant and Educator

Superior Equine Health and Nutrition Inc.

f.  @SuperiorEquine



1.  NRC's Nutrient Requirements of Horses, 6th edition

2.  The Horse Nutrition Handbook, Melyni Worth

3.  Nutrition and Feeding Management For Horse Owners, Novak & Shoveller

4.  Feed Your Horse Like A Horse, Juliet M. Getty

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