It would be an understatement to say we are slightly obsessed by levels of iron in the horse’s diet. We believe you should choose equine mineral products to ensure they contain the lowest iron content you can possibly achieve.
If you are intrigued or confused by the topic of iron in the horse’s diet then read on below.
Our own horses have benefitted enormously over the last 4 years by having minerals balanced to the forage they eat. This forage initially had high levels of iron which was impacting greatly on their health in many common, but significant ways. But why all the obsession?
"Iron is an important mineral, essential for life and abundant in the horse's diet. In addition it is probably the most over supplemented mineral. Iron is in virtually everything the horse eats; hay, grass, haylage, water, soil, commercial feeds, separates like oats and beet pulp and is added to the majority of the vitamin/mineral supplements on the market, however, it is not just the listed iron we needed to worry about, we need to worry about the 'hidden' iron in the feeds we feed."
The importance of iron in the horse’s diet
Iron is an important mineral, essential for life and abundant in the horse’s diet. In addition, it is probably the most over supplemented mineral. Iron is in virtually everything the horse eats; hay, grass, haylage, water, soil, commercial feeds, separates like oats and beet pulp and is added to the majority of the vitamin/mineral supplements on the market.
However it is not just the listed iron we needed to worry about, we need to worry about the ‘hidden’ iron in the feeds we feed.
Excess iron can literally be a ticking time bomb, building in the body, storing in the liver and spleen and has been reported in many other species, from several types of bird, black rhinoceros, tapir, lemur and dolphin.
Iron can be a dangerous mineral in excess because its high affinity for oxygen and high reactivity makes it easily absorbed. It is absorbed by binding to specific metal transporters in the small intestine and also passively via junctions between the cells.
Research in other species shows that volatile fatty acids (VFAs) which are produced from hindgut fibre fermentation enhance iron absorption in the colon. As the horse is a hindgut fermenter, this leads to the possibility of a significant source of iron.
High amounts of iron stored in the liver turn the insides of this organ black and worryingly, veterinary pathologists actually consider this to be a ‘normal finding in horses. The colour is from iron deposits called hemosiderin.
A recent study evaluated the potential link between insulin resistance (IR) and iron overload and linked iron status to IR 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.)
A potential link between insulin resistance and iron overload disorder in browsing rhinoceroses investigated through the use of an equine model. Nielsen BD, Vick MM, Dennis PM. Source Department of Animal Science, Michigan State University, East Lansing, Michigan 48824, USA. email@example.com Iron overload disorder afflicts captive rhinoceros but has not been documented in the wild. The specific cause for the disorder has not been identified but is likely associated with diet and management. Compared with wild counterparts, captive rhinoceros eat diets containing more iron, have greater fat stores, and exercise less. It has been suggested that the problem may be linked to development of insulin resistance in the captive population. Given that controlled experiments with sufficient numbers of rhinoceros are logistically not possible, an equine model was used to look for a relationship between iron status and insulin resistance; the nutritional requirements of horses are used as a guide for rhinoceros, because they have similar gastrointestinal tracts. Sixteen horses were tested to determine blood insulin responses to an oral drench of dextrose (0.25 g/kg bodyweight) and a meal of pelleted corn (1.5 g/kg bodyweight). Fasting blood samples were taken 30 and 0 min before administration. Further blood samples were taken every 30 min for 4 hr after administration to determine peak insulin and total area under the insulin curve (AUC). Fasting samples were tested for serum ferritin concentrations. Correlations were determined between ferritin and peak insulin concentrations and insulin AUC after administration of oral dextrose and pelleted corn. The strongest correlation was between ferritin and insulin AUC after dextrose administration (r = 0.61; P = 0.01) followed by AUC after feeding a meal of pelleted corn (r = 0.60; P = 0.01), with the correlation for peak insulin being 0.53 (P = 0.03) after dextrose administration and 0.56 (P = 0.02) after pelleted corn. When evaluating responses by gender, a significant correlation existed only for females, influenced by one insulin resistant individual. These data suggest a potential link between insulin resistance and body stores of iron and also suggest that approaches to reduce the susceptibility to insulin resistance should be incorporated into management of captive browsing rhinoceros.
In the future perhaps there will be studies exploring possible connections with iron status and arthritis and also with Cushing’s disease. Interestingly the changes that are seen in the brains of horses correlate with those seen in human brains when iron overload has been identified.
One problem with excess iron is the negative effect it has on the uptake of copper and zinc – two minerals that are usually already very deficient in horses’ diets. 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, (these ratios are in line with those published in the National Research Council’s Nutrient Requirements for Horses).
The only way to correct this ratio is to increase supplemental levels of copper and zinc.
Full mineral analysis of forage from hundreds of samples throughout the UK and Europe have identified clearly, time and time again, that iron is invariably in excess in forage. One sample in particular from Israel showed an astonishing iron level of over 1400 mg per kg! This means that the horses eating this forage were exposed to over two times the daily requirement in just one kilogram of forage-fed.
The high iron content of forage seems to have been totally overlooked by the feed industry and their nutritionists. In the rare case that there is a very small shortage it can always be supplied by feeding a small amount of alfalfa or beet pulp, feeds which both contain very high levels of iron. It is very very rare that iron supplementation is recommended in a horse’s diet because it is so over supplemented in forage.
The same also applies to manganese which is very rarely seen at deficient levels in forage and is usually grossly in excess. Manganese in excess works to make the over absorption of iron even worse due to this minerals affinity for attaching to ferritin. Ferritin is one of the body’s ways of regulating the uptake of iron but if excess manganese attaches to the available ferritin then this fail-safe ceases to operate.
Balancing our horses trace minerals
When we began balancing our horses’ trace minerals, we saw a big improvement in their hooves, coats and skin. There were high levels of iron and even higher levels of manganese contained within the forage they were eating. Copper and zinc were at very poor levels.
Once the ratios between these minerals were corrected through increased supplementation of copper and zinc, repeat abscessing and white line disease reduced then dwindled away to virtually nothing.
Skin infections that our vet had been unable to shift for years with topical applications disappeared within weeks and coats became darker with a wonderful lustre and sheen that no shampoo had ever been able to produce.
Our thoughts were that if this was what could be seen on the outside then there must be more changes on the inside! In many other horses, arthritic problems have improved and IR problems have slowly become less.
Excess iron in the diet has been linked with predisposition to infection, arthritis, risk of tendon/ ligament problems, as well as altered glucose metabolism. There is also a suggestion in human research that the low availability of copper predisposes the lining of the digestive system to increased inflammation.
Six months on mineral balancing where iron absorption was reduced by correcting ratios of copper and zinc and this pony showed much-improved coat colour and his lung allergy was significantly improved.
His immune system improved to beat a lung infection that had not responded to antibiotic treatment. He had also shown anaemia, even though treated with an iron tonic. Anaemia in horses is usually to do with a deficiency of copper, not iron and iron tonics often make matters much, much worse. Note the frizzy, ginger look to his mane in the first picture.
The same iPhone camera was used to take both shots.
You should try to find a balancer that does not include added iron or manganese because the common profile of forage, both here in the UK and Europe, shows that supplementing more of these minerals is just not going to help achieve optimum health in any horse.
We don’t believe a broad/multi-spectrum approach is suitable for achieving optimum health in horses, we recommend a forage focussed supplement, targeted specifically to match only those minerals which are commonly deficient in that which is the greatest proportion of the horse’s diet, forage.
Try to find a supplement where the magnesium oxide used contains less than 50ppm of trace iron. Using an ultra-low iron, forage focussed balancer will help limit the amount of iron your horse is exposed to. Do not accept substandard mineral sources.
However, you will find iron as a trace element impurity, a hidden source of iron in many minerals commonly used in equine feeds and supplements particularly in magnesium oxide.
Those supplements which use standard animal feed grade magnesium oxide for formulating their feeds and supplements will typically be high in hidden iron. Close inspection of the iron levels in this source of magnesium oxide will reveal high amounts of trace contamination.
The commonly used animal feed grade contains as much as twenty thousand parts per million (20,000ppm) of trace elemental iron. By comparison good quality, human pharmaceutical grade magnesium oxide contains typically between 20ppm and 50ppm of iron which is up to one thousand times less elemental iron than in regular feed grade magnesium, however, the only way to tell is to ask for the technical specification of the mineral.
By feeding balancer supplements that are specifically formulated to be ‘ultra low’ in iron and focussed on the common deficiencies in forage you can help your horse reduce dangerous excess iron exposure. There are many common problems seen in horses that can be eliminated by lowering the absorption of iron. We have listed some of these below.
- Does your horse have thrush and/or white line issues that won’t go away, even with great hoof care and topical thrush treatments?
- Does your horse suffer from bouts of mud fever even when the ground is not muddy?
- Is your horse hard to get fit and seem to tire easily?
- Does your horse suffer from sensitive hooves, even though they look great from the outside and have good trims on them?
- Does your horse have issues tolerating sugars (but does not test for insulin resistance) or is even insulin resistant?
- Does your horse have scruffing/flakey skin and is itchy all the time, even when not sweating and with feeding flax and good grooming?
- Does your horse eat a lot of soil, eat tree bark, branches, bushes, other ‘odd’ plants, even though it has tons of food and isn’t bored?
- Does your dark colored horse bleach out every summer, does you chestnut horse look pale and pasty, does your horse have a ‘dull’ colored coat or have have frizzy ended hair.
- Does your horse suffer from allergies (skin or lung) or other immune issues?
- Does your horse suffer from unexplained laminitis (or has sugar sensitivity related laminitis), blow abscesses for no reason, has thin soles, etc?
- Does your horse have cracks in the outer hoof wall, cracks in the inner wall between the white line and sole, bad hoof quality in general?
If you answered yes to any one of those questions then maybe you need to look into the trace elements which are ‘hidden’ in your horse’s diet. Don’t just look at that listed on the side of your bag of commercial feed or supplement tub, look into that contained in your forage and look into that contained within the very minerals used to supplement your horse.
If you are confused by this and would like to know how to understand the numbers surrounding the trace metal content of a mineral then read here. Understand that the listed iron is not the whole story.
Understand that you need to look into the hidden and impurity levels in all areas and be committed to sourcing the very best ingredients for your horse that are as free from impurities as you can make them. Iron is everywhere but you can minimise it so that it is in your horse’s diet at safe and healthy levels.
Learn more about Horse Health here.
Last Updated on December 23, 2021 by Forageplus Team