We talk about optimum feeds for the horse all the time, but we frequently do not delve into the details of the minor trace minerals. Zinc and copper are critically important to the horse. They are available as individual products, such as Bioplex® Zinc and Bioplex® Copper, or as Zinc-Copper Combo, which provides these highly absorbable minerals premixed to the optimum 3:1 ratio. This newsletter will shed more light on why they are so vital.
◆︎ The Role of Zinc
➡ Zinc plays a vital role in tissues that undergo rapid growth and cellular turnover, such as the hoof wall and intestinal lining. It is the key element for “zinc finger proteins,” which act as chemical signaling messengers that prompt or inhibit specific gene transcription. Without zinc, the genetic instructions for cellular division—especially in the hooves and gut—cannot be successfully transmitted.
➡ Zinc is also required for the activation of matrix metalloproteinases (MMPs). This is important because these enzymes govern tissue remodeling, which occurs during wound healing, hoof growth, and tissue repair. While many people think of MMPs as destructive enzymes to be avoided (especially during a laminitis episode), they actually play a necessary, critical role in the repair of damaged structures.
➡ Finally, zinc is a frontline antioxidant. While we usually think of vitamin E or selenium as the horse's primary antioxidants, the first line of intracellular defense is the SOD (superoxide dismutase) enzyme pathway. In this specific enzyme, zinc acts as the structural anchor to stabilize the enzyme’s shape, while copper drives the actual neutralization of damaging free radicals.
◆︎ The Role of Copper
☛ Copper is key for several systems within the horse. The most frequently discussed role is the synthesis of connective tissue. Copper is a required cofactor for lysyl oxidase, the enzyme responsible for cross-linking collagen and elastin. This is critical for growing horses, but is equally important for horses recovering from injury. Collagen provides the structural scaffolding for skin, bone, cartilage, and tendons. Any injury to those structures relies on copper-dependent lysyl oxidase to rebuild tissue tensile strength.
☛ Copper is also heavily involved in iron mobilization. When iron is released from tissue storage, it is in a +2 state. However, it must be converted to a +3 state to be safely transported through the blood without causing oxidative damage. This conversion relies on the ceruloplasmin pathway, which is entirely dependent on copper.
☛ At the cellular level, copper is involved in energy metabolism via the electron transport chain; without it, the creation of cellular energy (ATP) would cease.
☛ Outwardly, the role of copper we recognize best is pigmentation. A "bleached out" summer coat, red rusty tips on a dark mane and tail, or frizzy, split ends in the hair may indicate inadequate copper stores.
◆︎ The Absorption Issue
Copper and zinc are naturally present in the forage the horse eats. However, the raw amounts present in the grass or hay do not tell the whole story.
Minerals compete for absorption in the gut. Iron competes with zinc for binding sites, and zinc competes with copper. If a horse grazes on pasture that has iron-rich soil, or consumes hay with a significant amount of dirt on it, the massive iron intake will physically block the absorption of both zinc and copper.
This brings up the concept of an absolute (frank) deficiency versus a relative deficiency. In an absolute deficiency, the diet simply does not contain enough copper or zinc to meet the horse's daily baseline needs. In a relative deficiency, the diet mathematically contains adequate copper or zinc, but there is so much iron competing for the receptor sites that the essential trace minerals are not absorbed and excreted.
◆︎ Supplementation
So, how do you know if you have a balanced mineral profile in your forage? You test your hay or pasture. A hay analysis will tell you exactly how much copper and zinc you have, as well as the amount of iron present to compete with them. To prevent these minerals from blocking each other, the optimum dietary ratio of zinc to copper is 3 to 1, which is the ratio in Zinc-Copper Combo.
If testing your specific hay isn't possible, you can utilize resources like the Dairy One forage database (available here). When reviewing their global feed data, you will see that in many instances, iron levels are drastically higher than zinc or copper. While regional averages are not a perfect substitute for testing your own feed, they provide a baseline indicator that is much better than a pure guess. If you cannot test, rely on visual indicators: a bleached coat, poor immunity, or crumbling, brittle hooves often point to an unbalanced ratio.
◆︎ Veterinary Care
If you have any questions or concerns about your horse’s nutritional health, you should always consult with your veterinarian. They are in a much better place to determine exactly what your horse needs than an impersonal newsletter, Facebook post, or Google search.
We do the best we can for our horses. Understanding our horse's needs is a part of that.
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Disclaimer: Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.
©Joan Kulifay, MSc. 2026