JB said it all :yes: I always learn from their posts! I’ve found the Iron, Zinc and Copper function and relations to be a super interesting topic and hopefully you do too OP. There is so much information out there on it and some good studies to read, if you are interested in that sort of thing.
The 900ppm of iron is 900 mg/kg of Tribute fed, so you would convert the amount of lbs of Tribute you are feeding to kg, then multiply 900 by that number and you get the number of mg of iron per serving. Not sure if you were necessarily asking that or not? As has been already stated, it is not necessarily the Iron itself that is the problem, but actually the amount of iron in relation to copper and zinc (at 4 Fe: 1 Cu: 4 Zn ratio is suggested), which compete for receptors in order to get absorbed. Hence, if you have too much iron, then copper will not be effectively absorbed at an amount that would balance Fe affects. Anemia CAN happen, but nutritional causes are relatively rare because often Iron is sufficient enough in the environment to meet requirements and also as stated, there are so many feeds that have iron in them WITHOUT enough copper/zinc to balance it out. More often, anemia is a caused from bleeding (external, ulcers-internal), pathophysiology that destroys RBCs (parasites and immune compromising disorders such as virus’ and infections) or causes the horse not to produce enough of them (diseases affecting route of production or displace them).
And the problem with blood tests for iron is that they are so variable, as JB has written about. They really should be compared with other results for a better overall picture. Additionally, iron actually depends on a copper-dependent enzyme called hephaestin to be transported from the intestine into the blood via oxidation. It converts the Iron to a state that can be transferred in the blood (Fe^2+ --> Fe^3+). In cases of copper deficiency, iron absorption and thus, blood hemoglobin levels, may be reduced due to reduced activity ofhephaestin. In other words, copper deficiency can actually cause the result of low iron (anemia), when in fact, the cause is low copper too. That is why blood tests need to be taken with a grain of salt and personally, I wouldn’t immediately jump on Iron supplements without further investigation. Unless there is other reasons to believe that that iron is truly lower than copper (see above).
Too much Iron isn’t necessarily harmful to a horse’s well being, but can affect places where copper is well needed such as hooves and possibly soft tissue for example. It is just something to be aware of that most often, a horse is in need of more copper nutritionally (not as prevalent) than iron. Certain horses, such as IR horses are more sensitive to excessive iron in relation to the copper and zinc. Iron overload, meaning excessive iron (10 Fe to 1 Cu) quite past that recommended (4:1) is where you may see more change. I know someone who had a ton of iron on their property (in water, hay, soil etc) and their horses actually did exhibit more extreme signs of iron overload such as bad quality in hooves, ligament/tendon issues, and one even had a heart issue. I would say MOST places are not to that extreme, but when the vet and her fixed the Fe: Cu: and Zinc balance, the accumulative issues went away. They did have to go to extremes in that case though - water filter, blood letting recommended by vet) and high copper and Zn supplementation.
So, Iron IS needed, but at a balance with copper and Zinc because in many ways, they work together. Typically, it is recommended at 4 Fe: 1 Cu: 4 Zn. Those are just ratio guidelines, but obviously cannot be fixed in reality. iron is used to make certain proteins, particularly the component that carries oxygen - hemoglobin and myoglobin (found in muscle). It is also used as a component of enzymes (often protein) in the synthesis of collagen and some neurotransmitters, plus iron assists in immune function.While needed, Iron is also an oxidant like oxygen and can contribute to the production of free radicals or in other words reactive/unstable oxygen species - they need another electron to be ‘balanced’ and thus try to by binding to nearby lipids, proteins and nucleic acids. They are generated in a number of reactions essential to life and why everyone ages!, but can also cause damage to cells.
Antioxidants, such as copper (superoxide dismutases - enzyme complex of copper and zinc) counter the oxidant affect. You want a balance. When either copper or iron deficiency occurs, oxidative stress levels may go up. Dietary copper is recommended to be at least 100mg/ day, but that is relative to iron/zinc levels. Remember that if you have high zinc or iron, you’ll need more copper than 100mg! Copper is involved in a number of metabolic pathways such as those involved in iron metabolism, connective tissue formation, energy production, central nervous system function, and melanin production. You’ve probably heard lots of talk on here about the affect of copper deficiency on hoof quality and I’ve also mentioned the affect on soft tissues here. That is because copper is involved in an enzyme that facilitates cross-linking of collagen and elastin in connective tissues. these tissues are in soft tissues and the white line in the hoof.
Zinc is recommended to be at 400mg min daily relative to iron/copper. Zinc is also an antioxidant (superoxide dismutase) and plays a role in fetal development, growth, tissue repair, reproduction, the immune system and stabilizes protein structures involved in functions. In hooves, zinc facilitates keratin production, adding to the strength of hooves.
