Animals need iron. It is an essential mineral that plays an important role in maintaining a horse's health. It is involved in several key bodily functions, including the production of hemoglobin, which carries oxygen to cells, and the maintenance of healthy muscles, bones, and organs. However, too much iron can be harmful, causing damage to DNA, cell membranes, and has been associated with insulin resistance and laminitis. In this article, we'll explore the role of iron in the equine diet, how much horses need, and the best ways to provide it.
Why is iron essential for horses?
Iron is a mineral that is vital to maintain a healthy body. As you probably learned in elementary science class, iron is vital to the transport of oxygen throughout the body (it makes blood and muscles red). It is also needed for thyroid hormone production and helps inside mitochondria (the cell’s powerhouse). Iron is incredibly helpful, it is also incredibly reactive. When there is an excess of iron, it can create ferocious free radicals called hydroxy radicals. These then generate more radicals, creating a chain reaction of destruction to cell structures and membranes.
People often go with “if a little is good, then more is better”. This is NOT how you want to approach nutrition. According to Dr. Kellon, VMD, there has NEVER been a documented case of iron deficient anemia in an adult horse “ever”. However our concentrated feeds, supplements, and mineral blocks are often loaded (even overloaded) with iron. So it is important to understand how much your horse actually needs so they don’t go into iron overload.
How much iron do horses need?
Horses require varying amounts of iron depending on their age, weight, and activity level. Adult horses generally need around 40-80mg of iron per day, while pregnant mares and growing foals may need up to 100mg per day. Working horses and performance horses may also require higher amounts of iron to maintain their energy levels and endurance.
The bioavailability of iron in a horse's diet can be influenced by several factors, including the form of iron consumed, the presence of other nutrients such as vitamin C and copper, and the pH of the horse's gut. Certain substances, such as tannins found in some plants, can also inhibit iron absorption.
Hay and grass are the primary sources of iron in most horses' diets. The iron content of these plants can vary widely depending on the type of grass or hay, the soil quality, and the stage of growth at which they were harvested. In general, legumes such as alfalfa tend to be higher in iron than grasses. Most grains used in horse feed, such as oats and corn, are relatively low in iron however, fortified feeds and supplements often contain added iron and added together can be more than is necessary or healthy.
*Note: Legumes also contain tannins. Natural water sources can also be filled with tannins leeched in from rotting wood.
Natural supplementation to help other conditions can also have excess iron. Dried seaweeds such as kelp and chlorella are high in iron, as is alfalfa. Just because it’s natural, does not mean it’s safe. Many treatments for metabolic conditions in horses recommend kelp. These horses can be particularly sensitive to iron overload, so be careful with the quantities you feed.
What are the symptoms and treatments for iron overload?
While there are surely side effects to iron deficiency, since there are no documented cases of it in adult horses, we’ll skip to the thing you should be concerned with - OVERLOAD. Iron overload in horses can cause a range of symptoms, including changes in coat color, hoof issues such as laminitis and abscesses, and even metabolic syndrome and insulin resistance.
Being a mineral, iron can accumulate. It tends to take up residence in the liver. This is a common condition in horses, where iron deposits called hemosiderin accumulate in the liver. Many equine necropsy’s (autopsy for animals) show iron loaded black livers. So common in fact it is considered ‘normal. Liver damage or failure does occur in horses, but it is late stage. Earlier symptoms include fatigue, joint pain/arthritis and often metabolic syndrome/insulin resistance.
Diagnosis of iron overload can be done through specific blood tests that measure serum iron, transferrin, and ferritin. Serum iron alone only tells you the iron in the diet and not the amount stored in the body. Calculations need to be made between these three measurements to give you a more accurate picture of the amount of iron in the horse's body. Keep in mind, high ferritin readings can point to iron overload or chronic disease involving inflammation or infection. This is a complicated process and requires the help of qualified staff to correctly draw and analyze the blood. *The comparative hematology laboratory at Kansas State Veterinary Diagnostic Laboratory is currently the ONLY lab to measure equine ferritin.
Equally complicated is the reduction of iron in the body. The ways to revert iron overload are not for the faint of heart. Even if you skip the ‘bloodletting’ you are left with a very strict diet which can take a year or longer to bring iron levels back to normal. It is far easier to not overfeed this mineral in the first place than to have to figure out ways and means of removing it.
TLDR:
Iron is an important mineral for maintaining a horse's health and wellbeing. It plays a vital role in carrying oxygen to cells, thyroid hormone production, and maintaining healthy muscles, bones, and organs.
Iron overload generates free radicals that damage DNA, cell membranes, and has been associated with insulin resistance and laminitis in horses.
Signs of iron overload included; changes in coat color, hoof issues such as laminitis and abscesses, and even metabolic syndrome and insulin resistance. Iron overload is only diagnosed via comprehensive blood tests and analysis.
Hay, grass, supplements, and mineral blocks are the primary sources of iron in most horses' diets and can often exceed the ideal daily intake (40-80mg). It is important to evaluate the amount of iron your horse is receiving prior to additional supplementation.
Work with your local county extension office or university to run soil samples. Collaborate with your veterinarian to run the necessary bloodwork. And get help from your local equine nutritionist, or online resources such as MadBarn or Balanced Equine, to help you determine your equine nutrition needs. Iron (and other minerals) can be complicated to determine within the diet, an expert can help you demystify the process.
Resources and Further Reading
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/hydroxyl-radical
https://forageplustalk.co.uk/iron-overload-in-horses-by-dr-kellon/
https://madbarn.com/high-iron-horses/
https://www.americanfarriers.com/articles/8630-too-much-iron-can-be-detrimental-insulin-resistant-horses (lots of good links in the comments)
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