Spring Grass and Horses: Risks Beyond Laminitis

Every spring, it’s the same conversation.

The grass comes through, the fields look great again, and suddenly everyone is on laminitis watch. It’s a real risk, and it deserves the attention it gets.

But if you spend any time working hands-on with horses, you start to notice something else. A lot of horses don’t look quite right at this time of year… even when laminitis isn’t part of the picture.

They’re a bit sharper. A bit tighter. Maybe not lame, but not moving freely either. Owners often describe them as “just fresh”.

Sometimes that’s true.

But not always.

Spring Grass Isn’t Just “Better Grass”

It’s easy to think of spring turnout as a simple upgrade from winter forage. More grass, more movement, happier horses. The reality is a bit more complicated.

Spring grass is chemically different. During rapid growth—especially those bright, cold days we tend to get early in the season—grasses can accumulate higher levels of sugars, particularly fructans (Longland & Byrd, 2006).

Those sugars don’t always get fully processed in the small intestine. Instead, they pass further down into the hindgut, where things can start to shift.

And that’s where a lot of these subtle issues begin.

The Gut Is Often the Starting Point

When large amounts of fermentable carbohydrate hit the hindgut, microbes get to work quickly. The by-product of that fermentation is acid, and if enough of it builds up, the environment becomes less stable.

Hindgut Acidosis is the term you’ll see in the literature, but in practice, it doesn’t always show up as something dramatic. More often, it’s low-grade.

A horse that’s not quite settled. One that suddenly reacts to things that never bothered them before. One that feels tight through the back for no obvious mechanical reason.

Research has shown that these shifts in hindgut environment can influence inflammation and gut permeability, even when clinical signs are mild.

So while laminitis sits at one end of the spectrum, there’s a whole range of less obvious responses happening alongside it.

“He’s Just Fresh”… or Is He?

Because a lot of what we see in spring can be brushed off as normal seasonal behaviour. More energy, more time out, a bit of attitude. But when you look a bit closer, the picture isn’t always that simple.

A horse that suddenly becomes reactive, inconsistent in the contact, or reluctant to move forward isn’t always being difficult. Sometimes they’re uncomfortable.

There’s increasing recognition that internal discomfort—particularly from the gut—can influence behaviour and posture. Not in an obvious, dramatic way. Just enough to change how the horse moves and responds.

And because it’s subtle, it’s easy to miss.

Colic Risk Quietly Creeps Up

Spring is also a time when we tend to see more cases of Equine Colic, especially the milder forms that don’t always make it as far as a vet call. Gas colic, spasmodic episodes, that sort of thing.

Often, it comes down to how quickly the diet changes. Moving from predominantly hay to rich pasture isn’t a small adjustment for the gut, even if it feels like a natural one.

Studies have consistently shown that sudden dietary change is one of the biggest risk factors for colic (Cohen et al., 1999). Spring turnout fits that pattern perfectly.

Not every horse will show obvious signs. Some just become unsettled, or a bit off in themselves for a few days at a time.

The Metabolic Horses Don’t Always Shout

For horses with underlying metabolic issues, spring can be even more of a balancing act.

Equine Metabolic Syndrome and Insulin Dysregulation are usually discussed in the context of laminitis, but the effects don’t start and end there.

Some of these horses won’t go lame. Instead, you might see weight creeping on quickly, changes in energy levels, or a general sense that they’re not coping as well as they should.

What’s happening underneath is a heightened insulin response to sugar intake. And while laminitis is the headline concern, that metabolic stress has wider effects on the body. Again, subtle. But not insignificant.

When It Shows Up as a “Body Problem”

One of the more interesting patterns in spring is how often these internal changes present as something that looks musculoskeletal. A horse comes in tight through the back. Maybe a bit uneven behind. Not lame, just not right. You treat, they improve… and then a week later, you’re looking at the same thing again.

In some cases, what you’re seeing isn’t a primary mechanical issue at all. It’s a response to something deeper—often low-grade discomfort that’s altering how the horse is using its body.

Over time, those patterns can become ingrained. That’s where it’s easy to fall into the trap of treating the symptom repeatedly, without addressing what’s driving it.

The Muscle Horses Struggle Too

Then there are the horses that just don’t feel like they have a handbrake off. Stiff, reluctant, not wanting to go forward. Sometimes labelled as lazy, sometimes as unfit.

For horses with Polysaccharide Storage Myopathy, spring grass can be part of the problem. These horses don’t handle high levels of dietary sugars well, and it can show up as muscle discomfort or poor performance.

Dietary management is a key part of managing PSSM, which makes sudden access to rich pasture a bit of a challenge.

Stepping Back a Little

None of this is about overcomplicating things. And it’s not about turning every spring issue into a clinical problem. But it is about noticing patterns.

If a horse changes—behaviourally, physically, or in performance—and that change lines up with turnout, it’s worth considering the role of grass. Not just from a laminitis perspective, but more broadly. Sometimes the right answer isn’t more treatment. It’s a different conversation entirely.

Final Thought

Laminitis deserves the attention it gets. That’s not up for debate. But it’s only one piece of what spring grass can do. Plenty of horses won’t show you a problem in their feet. They’ll show it in how they move, how they behave, or how they feel to ride.

And if you’re not looking for that, it’s easy to miss.

Learn more in our Equine Nutrition Advisor Certificate Program

References

Longland, A. C., & Byrd, B. M. (2006). Pasture nonstructural carbohydrates and equine laminitis. Journal of Nutrition.

Cohen, N. D. et al. (1999). Risk factors for colic in horses. JAVMA.