Are We Accidentally Poisoning Our Horses?

We’re told never to let horses near “toxic” plants such as deadly nightshade, ragwort, and foxglove. We feel like bad owners if we don’t pull every last bit of ragwort, and we judge others whose fields are full of it. But we rarely have the other half of the conversation: any plant can become toxic if consumed in excess, and many of us are unintentionally over-exposing our horses to daily, low-level toxicity simply by giving them no alternative forage.

“The Dose Makes the Poison”

Alle Dinge sind Gift, und nichts ist ohne Gift; allein die Dosis macht, dass ein Ding kein Gift ist.  All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison.

 — Paracelsus, 1538 (Father of Toxicology)

This principle,  “the dose makes the poison”,  reminds us that it’s not what something is, but how much of it is consumed that determines harm.

Horses evolved to thrive on a diverse range of vegetation: grasses, herbs, wildflowers, legumes, hedges, tree leaves, seaweed, berries... This natural variety allowed them to balance their intake instinctively. They ate a little of one thing, a little of another, never too much of anything.

Native ponies grazing on diverse common land. Sedges, Rushes and Reeds can all form part of a balanced diet for horses

The modern horse’s diet looks very different (Learn more from our previous blog here). Most have access only to grass, whether fresh, dried as hay, or made into haylage. And not just any grass, often the same few species, grown intensively for yield, not nutrition.

We continue to overseed with grasses and offer them freely, even though this “monoculture” of grass-based feeding has been linked to obesity, Equine Metabolic Syndrome (EMS), laminitis, acidosis, and gastric ulcers, all stemming from the same root cause: too much sugar, too much starch, not enough vitamins and minerals.

Ironically, it’s only when horses develop acute laminitis that we finally restrict their grass intake, by which point, it’s already too late. In the meantime, horse owners are told to avoid ryegrass because of its sugar levels, but not other grasses, which can be just as high in sugar, and still appear in “laminitis-safe” seed mixes. We’re told to avoid short, stressed grass because it’s sugary, and to wait until grass grows long, but once the long grass seeds, the sugar concentrates in the seed head.🤦

All of this well-meant advice misses the real issue:

We feed horses too much grass, too much of the time.

We don’t give them the diversity they evolved to need.

Most pastures and hay fields contain only a handful of grass types; ryegrass, timothy, fescue, meadow grass, cocksfoot, and bent grass. Some seed mixes include herbs, but they make up less than 5% of the total. In contrast, unmanaged meadows naturally contain 20–40% wildflowers and herbs.

Wildflowers are typically lower in sugars and starches, and richer in the vitamins, minerals, and phytonutrients that horses rely on for their health and wellbeing.

A Step Toward Balance

This is why we created the British Rewilding Mix, a blend of 15 wildflowers, herbs, and legumes designed to be sown into existing pasture or enrichment areas on tracks and equicentral systems. It’s not about banning grass, it’s about bringing balance back. While this seed mix wasn’t designed for haymaking, there’s no reason hay couldn’t be made from fields containing these species.

As with all plants, moderation matters.  If a horse only had access to one species, even a “beneficial” one, problems could arise. But in a diverse, living pasture, horses can once again self-regulate naturally. The risk of overconsumption is much lower, when horses have the opportunity to eat alternative types of fibre when hungry.

Sycamore seeds can contain Hypoglycin-A (HGA) which is linked to atypical myopathy.

Of course, not every plant belongs in a horse’s field. Some species, such as sycamore, pose a high risk even in small amounts and are best removed to be on the safe side. It’s also worth keeping an eye on plants that horses rarely graze, as they can become dominant and crowd out other species. Rewilding to support horses' health and wellbeing isn’t about letting nature run wild, it’s about working with nature as mindful stewards, creating pastures that are both safe and sustaining.

A Call to Courage

Change can be uncomfortable. It’s easier to keep doing what we’ve always done. To reseed with the same grasses, to feed from the same bags, to follow tradition because “it’s what everyone does, we’ve always done it that way.” But, the science is catching up with what horses have always known: health comes from diversity, not uniformity.

So this is an invitation to be brave. Question the norm, Experiment, bring back the trees, hedges, herbs, and wildflowers that belong under your horses’ feet.

Your horse doesn’t need perfection. They need choice.

Nature knows how to provide it. Just give it a hand to come back, then let it.