If you have spent any time reading about equine nutrition, you have probably noticed that selenium and vitamin E are almost never discussed in isolation. They appear together in research, in product formulations, and in veterinary recommendations with a consistency that is not coincidental. These two nutrients operate as a functional unit at the cellular level, and the way they interact explains why buying them formulated together is often the more logical choice than sourcing them separately. This post breaks down the mechanism, explains why the pairing matters, and walks through who Mad Barn’s Natural E/Organic Se is the right product for — and who should be looking at a different product in the lineup instead.
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Why These Two Nutrients Work as a Pair
The biochemical relationship between vitamin E and selenium is one of the more well-established nutrient interactions in equine nutrition, and understanding it makes the product logic much clearer.
Vitamin E is a fat-soluble antioxidant. Its primary role in the body is to protect cell membranes — particularly the phospholipid bilayer that surrounds every cell — from oxidative damage. During exercise, metabolism, and normal cellular function, reactive oxygen species are generated as a byproduct. Left unaddressed, these free radicals damage cell membranes, a process called lipid peroxidation. Vitamin E interrupts that process. It donates an electron to neutralize the free radical, but in doing so it becomes oxidized itself — a spent form of the vitamin that is no longer active as an antioxidant.
This is where selenium enters the picture. Selenium is a trace mineral that functions as a core component of glutathione peroxidase, an enzyme that plays a central role in the body’s antioxidant recycling system. Glutathione peroxidase helps neutralize the peroxides that form during lipid peroxidation — and it also helps regenerate the spent vitamin E back into its active form. In other words, without adequate selenium, the antioxidant work of vitamin E is less efficient. The two nutrients do not simply complement each other; selenium is part of the system that keeps vitamin E functional.
This is the mechanism behind the paired formulation. It is not a marketing convenience — it reflects how the nutrients actually interact at the cellular level.
The Supply Problem: Why So Many Horses Fall Short of Both
Vitamin E has one reliable natural source: fresh green grass. The tocopherol content of forage degrades rapidly once the plant is cut and dried — hay delivers a fraction of what fresh pasture provides, and the degradation continues in storage. A horse on a hay-only diet, kept in a dry lot, or managed with limited turnout on dormant or overgrazed pasture is almost certainly getting substantially less vitamin E from forage than a horse with access to lush green grass. This is not a fringe concern; it describes a significant portion of horses in managed care, particularly through fall, winter, and dry summer conditions.
Selenium geography adds another layer. Much of the American Northeast, Pacific Northwest, and upper Midwest has selenium-deficient soils, which means the forage grown there is also low in selenium. Horses eating hay from deficient regions may not be meeting their selenium requirements through diet alone. Unlike vitamin E, selenium deficiency has a genuinely narrow margin — because selenium also has a narrow safe range on the upper end, more is not better, and supplementing without knowing baseline status carries real risk.
The only way to know where your horse actually stands on either nutrient is testing. Bloodwork for vitamin E and selenium status, combined with a hay analysis, gives you the actual picture. A veterinarian or equine nutritionist can interpret those results and guide supplementation decisions appropriately. This is not a post that will tell you your horse is deficient — that determination belongs to someone who has seen the numbers.
What I can tell you is that the combination of hay-based diets, limited pasture access, and regional selenium variability makes these two nutrients among the most commonly identified gaps in forage-based feeding programs. Mad Barn publishes a genuinely detailed research library covering vitamin E and selenium in horses — worth reading before you make a purchasing decision, and linkable through Mad Barn’s site.
Mad Barn Natural E/Organic Se: What the Formulation Delivers
Mad Barn’s Natural E/Organic Se is the straightforward answer for horses whose owners want to address both nutrients in a single, clean product. A few things worth understanding about the formulation specifically.
Natural vitamin E, not synthetic. There is a meaningful difference here. Natural vitamin E (d-alpha-tocopherol) is more bioavailable than synthetic vitamin E (dl-alpha-tocopherol). The natural form is preferentially retained by the body — research consistently shows higher plasma tocopherol levels from natural-source supplementation compared to equivalent doses of the synthetic form. Mad Barn uses natural-source vitamin E in this product. If you have been buying a generic vitamin E supplement without checking the label for the “d-” versus “dl-” distinction, it is worth revisiting.
Organic selenium. Selenium in supplements comes in two forms: inorganic (sodium selenite or sodium selenate) and organic (selenium yeast, selenomethionine). Organic selenium is generally better absorbed and retained, which matters when you are working with a nutrient that has a narrow safe window. The organic form allows more predictable, efficient delivery at appropriate levels — which is exactly what you want with a mineral where the margin between adequate and excessive is small.
What this product is not. It is not a complete vitamin and mineral balancer. It addresses two specific nutrients. If your horse’s diet has broader gaps — trace mineral deficiencies in zinc, copper, or manganese, for example — this product is not designed to fill those. A horse whose program needs comprehensive mineral support would be better served by a product like Omneity, or AminoTrace+ for metabolic and high-demand horses. Natural E/Organic Se is the right product when vitamin E and selenium are the confirmed or clinically suspected gaps, and the rest of the program is already adequately covered.
Who this is specifically suited to:
- Horses with confirmed or suspected low vitamin E and selenium status based on bloodwork or veterinary recommendation
- Horses on hay-only or predominantly hay diets with limited fresh pasture
- Horses managed in dry lots or with seasonal pasture restriction
- Horses in geographic regions with documented selenium-deficient soils, per vet or nutritionist recommendation
- Horses already on a complete vitamin/mineral program whose vet wants to add specific E and selenium support on top
Who should look elsewhere:
- Horses who need only vitamin E without additional selenium — Mad Barn’s standalone Natural Vitamin E covers that case without adding selenium to the mix
- Horses whose selenium status is unknown and who have not been tested — selenium supplementation without established baseline and veterinary guidance is genuinely risky; do the bloodwork first
- Horses who need comprehensive mineral balancing — start with Omneity or AminoTrace+ depending on the horse’s profile, and discuss E and Se levels with a nutritionist before stacking additional selenium
Ready to try Mad Barn Natural E/Organic Se? Use my link for reader benefits at Mad Barn → https://madbarn.com?ref=18219
How Natural E/Organic Se Fits Into a Broader Program
The most common question I hear about this product is how it fits alongside other supplements. The answer depends entirely on what the horse is already getting.
If your horse is on Omneity — Mad Barn’s complete vitamin/mineral premix — that formula already includes vitamin E and selenium at levels appropriate for baseline support. Adding Natural E/Organic Se on top would be stacking additional selenium without necessarily having confirmed a need for it. That is a conversation for your veterinarian or an equine nutritionist, not a default pairing.
If your horse is on AminoTrace+ — Mad Barn’s enhanced mineral formula for metabolic and high-demand horses — the same logic applies. AminoTrace+ includes natural vitamin E and elevated selenium within its formulation. Do not stack without professional guidance.
Natural E/Organic Se is most cleanly used in one of two scenarios: either as the primary supplement for a horse whose diet has been assessed and where E and Se are the identified gaps, or as a targeted addition to a forage-based diet with minimal other supplementation. In either case, the decision should be guided by actual testing, not by assumption.
I have talked about the decision-making process around targeted versus comprehensive supplementation on the podcast — the short version is that targeted products like this one work best when you have real data telling you what to target.
The Selenium Safety Note — Read This Part
I want to be direct about this because it is genuinely important. Selenium has one of the narrowest safe ranges of any mineral in equine nutrition. The margin between a beneficial level and a toxic level is real and documented. Selenium toxicity — selenosis — produces recognizable clinical signs and is not reversible once it progresses. This is not a “more is better” nutrient.
This means: do not add selenium supplementation to your horse’s program without knowing where he currently stands. Bloodwork is the tool for that. If your horse is already receiving a complete vitamin/mineral supplement, check whether it contains selenium before adding a selenium-containing product on top. Consult a veterinarian or equine nutritionist before supplementing. Do not estimate doses based on body weight without professional guidance — follow the product label and the advice of the professionals who know your horse’s individual status.
Mad Barn’s own published materials are honest about this, which is part of why I trust the brand on this product. A company that tells you to test before you supplement rather than just encouraging you to buy more is doing right by the horse.
The Bottom Line
Vitamin E and selenium are formulated together because they work together — that is biochemistry, not marketing. Natural E/Organic Se delivers both in their more bioavailable forms: natural-source vitamin E and organic selenium. For the right horse in the right situation — hay-based diet, limited pasture, confirmed or clinically supported shortfall, veterinary or nutritionist guidance in place — this is a clean, well-formulated product that addresses a real and common gap.
Buy it after testing. Use it as part of a program your vet or equine nutritionist has reviewed. And if the gaps in your horse’s diet are broader than just these two nutrients, start with a comprehensive balancer and work from there.
Ready to try Mad Barn Natural E/Organic Se? Use my link for reader benefits at Mad Barn → https://madbarn.com?ref=18219
