Iron Supplements in horses, dire need or marketing hype?
Iron (Fe) is a trace mineral that makes several biological contributions, including oxygen transport, cellular respiration and healthy immunity (Platnium performance, 2024). Hemoglobin, the component of the red blood cell that allows oxygen to be carried to the tissues, requires iron for its synthesis (Staff, 2018). It is an important element in the horses body, and its uptake is regulated by a hormone called Hepcidin. Hepcidin has a crucial role in the process that allows the horses body to relocate iron, store it and reuse it. The small intestine is the site at which iron is absorbed in the horse.
The horses body has the ability to recycle iron. When red blood cells die, the iron contained in them is reutilized in the production of other red blood cells. It is rare that there is a loss of iron within the horse. Iron deficiency in horses can occur, but from heavy parasitized horses or horses with severe gastric ulcers ( leading to blood loss) (Staff, 2018).
There is an overall idea that feeding iron provides energy for horses, increases hematological parameters (such as packed cell volume etc) and is a “pick me up” for horses. In an online poll I asked why horse owners fed an iron supplement, 43% said it was for overall health, 29% said it was for energy when the horse was in hard work and 29% said a nutritionist advised it. In a study investigating the effect of excessive iron fed to adult ponies (50 mg/kg of body weight), found that Packed cell volume, erythrocyte counts, and hemoglobin concentration did not change in the ponies being fed excess iron. It was also noted a pony had become anemic by week 3 of the 8 week study, and didn’t resolve with the feeding of iron. It was found the pony had numerous strongyles in the gastrointestinal tract that caused the anemia (Pearson & Andreasen, 2001).
How much do horses need?
According to the National Research Council (NRC), the horses diet requires 40 mg/ kg (of feed Dry Matter (DM)) for a mature horse and 50mg/kg DM for growing foals and lactating mares (NRC,2007)
So for a 500kg horse, this is 400mg of Iron per day
(2% BW = 10KG feed, X 40mg = 400mg)
A survey was conducted to determine the amount of iron fed to racehorses in the US. The results found that of the 1,978 racehorses that were represented, were fed an average of 3900 mg of iron per day from hay and grain alone. This exceeds the 400 mg for a 500 kg working horse that the NRC 2007 recommends per day (McLean et al., 2022)
What is the amount in feed and hay?
Looking at the typical 500kg horse, who is stabled and is fed approx. 20% hard feed – example RedmillS cool n cooked and 80% mixed grass hay, how much iron is the horse receiving.
The average amount of iron in mixed grass hay has been reported as 343 mg/kg DM (Equi-Analytical)
In Red Mills Cool n’ Cooked feed it is 120mg/ kg DM
If this horse is getting 2% of its body weight in feed a day (DM), that is 10kg. 80 % hay = 8kg and 20% feed which is 2kg
- 2 kg of cool n cooked = 240mg of iron
- 8 kg of hay = 2,744 mg iron
Total iron per day= 2,984 mg. The recommended amount of iron for this horse is 400mg
As we can see, this example horse is receiving over seven times its daily need of iron.
What does over feeding of iron do?
In a study looking into chronic iron overload in horses and one donkey (Theelen et al., 2018) found that all the animals had haemochromatosis, also known as chronic iron toxicosis. This was a result of excessive iron in their drinking water for 9 years. If horses have access to natural drinking water, it is best to get it tested.
What brands say about their iron supplement
Looking to the current supplement market, here are some of the iron supplements available:
- Iron Boost Plus (Nutriscience)
- Feratone (Foran)
- New Bludd (Horse First)
- Blood Booster (Ardmore)
- Iron Syrup (Plus Vital)
Below is some of the supplements information about their iron supplement:
New Bludd: “ A liquid iron tonic formulated to boost your horse's blood levels, aids the immune system, for overall health and wellbeing”
Iron Syrup: “ Iron boosting formula supporting red blood cell production, Iron boosting formula, supports red blood cell formation”
Below is a table with the daily amounts of Iron per dose from each supplement brand:
After searching the amount of Iron per supplement, I found that Mervue supplements didn’t provide the amount of iron in their supplement. Also, Horse First didn’t provide the volume to which the amount of iron was in (usually its per litre so that is what I used).
Conclusions
Overall, the majority of horses are not in need of an Iron supplement. Iron deficiency in horses is very rare and most horses receive far more iron than what is required from forage alone. Deficiency can occur if horses have blood loss or a high worm infestation. If your horse is in good health and a nutritionist advises an iron supplement, question why, as we can see there is no need in a healthy animal. Only feed an iron supplement to your horse if it has had a blood test, and is recommended to you by your vet.
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References
Iron in horses: Iron Horse Nutrition (no date) Iron in Horses | Iron Horse Nutrition. Available at: https://www.platinumperformance.ca/articles/iron-horse.html (Accessed: 01 March 2024).
Staff, K.E.R. (2018) Iron: An important trace mineral in equine diets, Kentucky Equine Research. Available at: https://ker.com/equinews/iron-important-trace-mineral-equine-diets/ (Accessed: 01 March 2024).
Nutrient requirements of horses (2007). Washington: National Academy.
Pearson, E.G. and Andreasen, C.B. (2001) ‘Effect of oral administration of excessive iron in adult ponies’, Journal of the American Veterinary Medical Association, 218(3), pp. 400–404. doi:10.2460/javma.2001.218.400.
McLean, N.L., McGilchrist, N. and Nielsen, B.D. (2022) ‘Dietary iron unlikely to cause insulin resistance in horses’, Animals, 12(19), p. 2510. doi:10.3390/ani12192510.
Equi-Analytical Laboratories Common Feed Profiles. [(accessed on 01 Mrach 2024)]. Available online: www.equi-analytical.com/common-feed-profiles
Theelen MJP; Beukers M; Grinwis GCM; Sloet van Oldruitenborgh-Oosterbaan MM; (2018) Chronic iron overload causing haemochromatosis and hepatopathy in 21 horses and one donkey, Equine veterinary journal. Available at: https://pubmed.ncbi.nlm.nih.gov/30269378/