When the Grass Isn't as Safe as It Looks: What Finlay Taught Me About Ragwort

I've spent most of my career studying things that can't be seen — the microscopic processes that decide whether a system stays healthy or starts to fail. I never expected that same lens to end up pointed at a patch of grazing in Northamptonshire, but that's exactly what happened when Finlay arrived.

She came to us in poor condition, underweight and worn down, and it took time — and a fair amount of detective work — to understand why. Ragwort was part of that picture. It's a plant most horse owners have heard of, but I don't think many of us really understand what it does, or why it's so unforgiving. As a microbiologist, I couldn't just accept "ragwort is bad" as the end of the story. I needed to understand the mechanism. So I went back to the science, and I think it's worth sharing what I found — not as a scare story, but as the kind of practical understanding I'd want any owner to have.

It's not the plant itself, it's what your horse's liver does with it

Ragwort contains compounds called pyrrolizidine alkaloids. On their own, they're not the problem. The problem is what happens when a horse's liver tries to process them. The liver is normally very good at breaking down and clearing out things that don't belong in the body — but with these particular compounds, some of what it produces in that process is more dangerous than the original plant. Those reactive by-products bind to liver cells and, over time, cause scarring that the liver simply cannot undo.

That's the part that changed how I think about it. This isn't a poison that passes through and is gone. It's cumulative. A horse can look completely fine while, quietly, month after month, small exposures are adding up.

There's no such thing as a "safe amount"

I'll be honest — when I started reading the research, I was hoping for a number. Some threshold I could point to and say "below this, don't worry." It doesn't exist. How much risk a plant poses depends on the individual plant, the time of year, growing conditions, and the horse itself. And critically, drying doesn't make ragwort safer — if anything, dried plant material is more palatable, which means it can end up somewhere far more dangerous than a field: in hay.

That's not a comfortable thing to write, as someone who wants to give owners reassurance rather than anxiety. But I'd rather be honest about the uncertainty than pretend there's a simple rule that doesn't hold up.

Why the signs are so easy to miss

Because the liver has such a large reserve capacity, a horse can seem outwardly normal for a long time while injury is building underneath. When signs do appear, they can be as easy to dismiss as dullness, reduced appetite, or a horse that's "just not quite right." It's only later, if things progress, that the more unmistakable signs show up — jaundice, sensitivity to sunlight on unpigmented skin, changes in coordination or behaviour. By then, the disease is often well established.

That gap — between quiet internal damage and visible illness — is, I think, the single most important thing for owners to understand. It's also why, once we understood what Finlay had been through, our focus shifted immediately to protecting whatever liver function she had left, rather than looking for something to reverse damage that had already happened.

What I'd ask every owner to do

• Walk your fields properly, not just a

  glance from the gate — ragwort can hide among longer grass.

• Check hay and haylage, not only pasture. This is where dried, more palatable ragwort becomes a real risk.

• Don't wait for multiple symptoms before calling your vet. Early, non-specific signs — dullness, a drop in appetite, subtle weight loss — deserve attention on their own.

• If you find ragwort, treat it as a management issue to solve, not a one-off task to tick off. Ongoing vigilance matters more than a single clearance.

  
  

Why I wanted to write this

Finlay's recovery is one of the things I'm proudest of at Scientia Sport Horses, and it's tempting to tell that story purely as a happy ending. But the science background I bring to this work means I can't leave it there. If sharing what actually happens inside a horse's liver helps even one owner catch something early, or double-check a hay supplier, or simply look a little more carefully at their field — that feels like exactly the kind of prevention this evidence points to as the only real defence.

It's also, in a strange way, a reminder of why I built this programme around evidence rather than instinct alone. Genetics, microbiome, environment, training — and luck. Finlay had good care and, eventually, good luck. Not every horse gets both. Understanding the science is how we tilt the odds a little further in their favour.

— Joanne