Iron Overload in Horses
I recently wrote an article for The Horse about a study which evaluated the potential link between insulin resistance (IR) and iron overload in horses. Interestingly enough, the study’s purpose was actually to investigate this link in browsing rhinoceroses, but since it’s difficult to get a large group of rhinos together, horses were used as a model. (The two species share a similar digestive tract.)
I have to say I was very excited to come across this study because: A.) I’ve been searching for new studies related to iron overload in horses for a while now, and B.) I have two IR horses, so this particular topic is of special interest to me.
In the study, the researchers mention that the relationship between iron (ferritin) and insulin resistance had not been previously explored in horses. Brian Nielsen, the lead researcher, even said that he’s been surprised by the amount of interest this study has generated (on the horse side of things), and that he and his colleagues may be looking into the issue further. I certainly hope so!
So here’s what I know about iron in the horses’ diet: It’s a trace mineral that is needed by the horse, but it is likely the most oversupplemented mineral in the horse’s diet. I think because iron-related anemia is more common in people, we tend to think it’s a problem for horses as well. But Iron is in nearly everything the horse consumes– grass, hay, dirt, water, most commercial feeds, and the majority of vitamin/ mineral supplements.
Horses only need about 40 ppm of iron to meet their daily requirements, but most equine diets far exceed that amount. For example, my hay analysis for last year showed 162 ppm of iron. (And to think, I once gave my barrel horse Red Cell, a popular iron supplement, at the start of the barrel racing season because he seemed a bit ‘lethargic’ to me. . .) Another point to remember about iron is this: horses have no way to excrete it–it’s stored in their liver and spleen.
Iron deficiency and nutrition-induced anemia are extremely rare in horses and may often be misdiagnosed (as discussed in the article, Horses–Natural Blood Dopers). Horses are much more likely to have problems with too much iron in their diet.
One problem with excess iron is the negative effect it has on the uptake of copper and zinc–two minerals that are often already deficient in horses’ diets–as well as manganese. Dr. Eleanor Kellon recommends an iron: copper: zinc: manganese ratio somewhere between 10:1:3: 3 to 4:1:3:3, with the latter ratio being recommended for IR horses.
The only way to correct this ratio is to add copper and zinc (and maybe manganese, although I’ve never had to do this). Personally, when I began balancing my horses’ trace minerals, I saw a big improvement in their hooves and coats, as evidenced in these before and after photos of my gelding, Bob.
Another downside to excess iron in the diet is that it has been linked with predisposition to infection, arthritis, risk of tendon/ ligament problems, as well as altered glucose metabolism (as shown in the study I discussed at the beginning of this post.)
The following are a few easy-to-spot signs of a mineral imbalance in horses (which likely result from too much iron):
- bleached or dull coat, mane, and/or tail;
- ongoing thrush
- brittle or cracking hooves (despite routine hoof care)
- poor hoof quality in general
So you may be wondering, what is the answer to dealing with excess iron in the horse’s diet? First of all, try to avoid commercial feeds and supplements with added iron (read the labels before you buy!) Many mineral blocks contain iron as well–I prefer to feed loose plain, white salt.
To correct trace mineral imbalances, either have your pasture and hay tested and work with an equine nutritionist to add deficient minerals individually (or take Dr. Kellon’s NRC Plus course, like I did!), or you can feed a mineral supplement like California Trace that has no added iron.
Another recent blog post on the EasyCare Inc. website discusses iron overload in horses as well–it’s worth the read.