Transcript:

[0:00]

Hi everyone, welcome back to Mad Barn Academy, and if you’re new here, welcome. If you like this presentation and the other videos on our channel, don’t forget to like and subscribe — we really appreciate the ongoing support. Today, we’re going to cover a topic that’s been quite popular on our social media recently: iron overload. Horses need iron in their diets — it is an essential trace mineral — but is it necessary to supplement extra iron? When does extra iron become too much iron? And what is iron overload actually? Let’s talk through some of these questions and an action plan if you’re concerned about high iron levels in your horse’s diet.

[0:48]

Iron is an essential trace mineral in the equine diet. Its most important role has to do with its high affinity to bind oxygen. Metalloproteins using iron are part of hemoglobin and myoglobin. Most of us recognize hemoglobin from high school science class — it’s required for oxygen transportation in red blood cells. Myoglobin is very similar to hemoglobin, just smaller, and it stores oxygen in muscle cells for cellular respiration. Iron is also essential to various biochemical processes in the body, such as DNA synthesis and ATP production during aerobic metabolism.

[1:38]

Iron deficiency in horses is extremely rare because horses are very well-adapted to absorbing iron from their gut. Horses are hindgut fermenters, meaning they break down fiber in their large intestine. The breakdown products of fiber fermentation, called volatile fatty acids, can actually enhance iron absorption from the colon as well.

[2:09]

The established requirement for iron in the equine diet is between 40 and 50 mg per kg of the diet, depending on the animal’s physiological status. It is accepted that horses will meet their iron requirements from forage and/or water intake alone, since most forages typically contain anywhere between 100 to 250 mg/kg (ppm) of iron. The maximum tolerable level of iron intake is thought to be around 500 ppm of the diet.

[2:53]

Visualizing these numbers in the diet can be hard, so here’s an example calculation. Take an average-sized horse at 500 kg (1,100 lb). Generally, horses consume about 2% of their body weight in dry matter daily, which equates to 10 kg of dry matter (simplified to 10 kg of hay). Plugging that into the iron requirement calculation: 10 kg × 40 mg/kg = 400 mg of iron daily for this horse.

[3:40]

Now, let’s see how much iron an average hay provides. Using 10 kg dry matter × 150 ppm iron = 1,500 mg of iron. That’s well above requirements but still within expected intake for average-quality hay. Compared to the maximum tolerable level (10 kg × 500 ppm = 5,000 mg), we’re still far below that threshold. Iron overload risk is from excessive intake day after day, long term — not from occasional higher amounts.

[5:08]

Many horses aren’t just on hay or pasture — they receive concentrates, ration balancers, or vitamin/mineral premixes. These products contain some iron naturally from plant-based ingredients and mineral salts. Some add extra iron, though not all list it on the label. To check, scan the ingredients for “iron” or “ferric/ferrous.” Also note that mono- or dicalcium phosphate often contains significant iron contamination.

[6:27]

What happens when a horse becomes iron overloaded? This is still under active research, with some extrapolation from human studies. Primary effects are direct effects of excessive iron; secondary effects are induced mineral deficiencies caused by excessive iron.

[7:05]

Primary effects include liver damage (since the liver is the main storage site for iron), oxidative damage (iron can form hydroxyl free radicals that damage cells), immune suppression (via impaired immune cell function), and possible exacerbation of insulin resistance (though it’s unclear if iron overload causes or results from it). Clinical signs are often non-specific and develop insidiously.

[8:54]

Secondary effects are due to induced deficiencies of zinc, copper, and manganese — all of which compete with iron for the same gut transport enzymes. More dietary iron means less absorption of these minerals. Clinical signs include poor hoof quality, brittle hooves, dull or bleached coat, and reddish ends on dark manes and tails.

[9:44]

Diagnosis is best made by measuring serum ferritin — the gold standard — available through Kansas State Veterinary Diagnostic Lab. Serum iron from routine bloodwork is unreliable due to fluctuations from recent meals. Additional diagnostics may include liver enzyme testing, ultrasound, liver biopsy, and insulin testing if metabolic disease is suspected.

[11:01]

Treatment involves dietary modification — reducing excessive iron intake and balancing minerals (often by adding zinc and copper). Milk thistle is also often recommended, as it’s both an antioxidant that supports liver function and an iron chelator, helping remove iron from the body.

[11:53]

Key takeaways: Horses generally meet iron requirements from forage and/or water alone, so high-iron supplements are unnecessary. If you’re concerned about iron overload, serum ferritin is the best diagnostic. To reduce iron intake, start with forage and water testing (water above 0.3 ppm may also taste metallic or stain buckets). Avoid high-iron supplements, and milk thistle can be used prophylactically. If unsure about diet balance, consult a nutritionist — we offer a free diet evaluation service.

[13:45]

Thanks for listening. I hope you found this helpful. If you’re concerned about high iron in your horse’s diet, these tools can help you determine if the concern is warranted and guide dietary planning. Don’t forget to like and subscribe, and check out the additional links in the description below. Until next time.