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Grasses, Ryegrass and Laminitis in Horses: What Every Horse Owner Should Know

  • siancc2021
  • Sep 23
  • 6 min read

Updated: Sep 27

Every spring and autumn, paddocks explode with green growth. For many horse owners, this brings not just joy but fear: Laminitis. Ryegrass in particular has gained a bad reputation, but is it really the culprit?

You may have heard:

  • “Short grass is safer as they can’t eat so much.”

  • “Long, unstressed grass is lower in sugar.”

  • “Soak hay, limit turnout and feed a balancer.”

Conflicting advice leaves horse owners frustrated, and sometimes, horses stressed. To truly understand the risks, we need to step back and ask: what role does grass — and ryegrass specifically — play in Laminitis?


Laminitis and High-Sugar Diets: The Bigger Picture

Laminitis is a serious condition in horses and ponies, but contrary to common belief, it’s rarely caused by sugar intake alone.

There are four main types of laminitis (Marcato, 2020):

Type 1: Sepsis/SIRS-related laminitis

Linked to systemic inflammation, often caused by bacteria.

Type 2: Endocrinopathic laminitis

Associated with underlying endocrine disorders such as Equine Metabolic Syndrome (EMS) and Pituitary Pars Intermedia Dysfunction (PPID, also known as Cushing’s disease).

Type 3: Pasture-associated laminitis

Where high non-structural carbohydrate (NSC) intake from grass triggers underlying endocrinopathic laminitis.

Type 4: Supporting limb laminitis

Caused by a fracture or infected joint forcing one leg to carry more weight, excessive foot trimming, improper shoeing, fast or intense work on hard surfaces, too much length of toe, or excessively high heels.



Most pasture cases fall into types 2 and 3. In these, excess insulin plays a central role: the horse already has an impaired metabolic system, and high-sugar intake pushes it over the edge (de Laat et al., 2019).

Recent advances mean SGLT-2 inhibitors (e.g., velagliflozin) can now be used to manage acute laminitis by lowering excessive insulin levels, helping to protect at-risk horses (Meier et al., 2018).

That doesn’t mean “healthy” horses can graze sugar freely. Diets rich in NSCs (sugar and starch) increase risks of colic, hindgut acidosis, and gastric ulcers (Colombino et al., 2022; Smarsh & Orr, 2024). Horses evolved to eat high-fibre, low-sugar forage, not dairy-cow pastures.


Ryegrass: Why the Concern?

Ryegrass isn’t inherently toxic, but it is high in NSCs compared to many other grasses (Rivero et al., 2019).

It was bred for dairy farming, where high sugar = higher milk yields. Modern tetraploid varieties (four chromosome sets instead of two) grow rapidly, produce dense swards, and outcompete other plants. This may be good for milk production but creates challenges for horses:

Higher pasture sugar content 

Means greater risk for laminitis-prone horses.

Reduced diversity

Means fewer alternative plants for horses to select from.

Faster regrowth

Means repeated flushes of high-sugar grass.

Even diploid ryegrass, sometimes marketed as “horse-safe,” still carries elevated NSC levels compared to traditional meadow species.

Ryegrass in horse pasture with no wildflowers or legumes to offer horses a balanced diet
Ryegrass seeded in an equine paddock with a variety of other grasses, but no wildflowers or legumes featuring in the grassland

What Horses Really Eat in Natural Grazing

When we picture horse pastures, we tend to think only of grass. But grass is not the “main meal” for horses, it’s more like dessert. Horses usually eat it first because it’s sweet and palatable, but in conservation grazing studies, their diet is much broader.

Native ponies in semi-natural habitats graze a wide variety of plants, including:

Grasses:

  • Yorkshire fog

  • Bromes

  • Bent grasses

  • Cocksfoot

  • Crested dog’s-tail

  • Red and Sheep’s fescues

  • Tufted hair grass

  • Sweet vernal grass

  • Wavy hair grass

(Jefferson, 2005).


In natural species-rich grasslands, wildflowers and legumes often contribute around 20-40% of natural forage providing protein, vitamins, and minerals which can act as beneficial secondary compounds (Defra Grass & Forage Science study; Jefferson, 2005; Reinsch et al., 2020).


Woody plants:

Hedgerows, shrubs, and tree bark, which supply fibre and beneficial secondary compounds.

Typical domestic management alters this natural diet diversity. Furthermore, foals are typically weaned at 4–7 months — about a year earlier than in feral herds (Henry, 2020). Early weaning exposes foals to grass sooner, potentially shaping their gut microbiome, influencing future forage preferences and predisposing them to future issues such as laminitis, but also acidosis, ulcers and colic. Foals weaned before 12 months may consume more sugary grass than nutrient-rich milk and may not learn to forage from shrubs and trees, which could affect long-term metabolic health (Tavenner, 2020).


Keeping foals with their dams longer and giving domestic horses more access to fresh, diverse forage also allows horses to self-select what they need and even self-medicate, a behaviour known as zoopharmacognosy (Neto, 2012). Horses are natural foragers, not grass-only grazers. To learn more, check out our previous article, "Is your horses diet like fast food?".

Gorse, this plant, while not grass can be part of a balanced equine diet
Gorse: A shrub found across the UK that would have been a staple in the diet of many native ponies

Rethinking Pasture for Horse Health

Feeding soaked hay and processed balancers may control sugar intake, but it’s like a human living on porridge and multivitamins — technically adequate, but far from ideal.

Horses thrive when they can:

  • Graze a variety of grasses — including traditional, lower-sugar species.

  • Access legumes and wildflowers — essential protein, vitamins, and minerals.

  • Browse shrubs and trees — for roughage and enrichment.


This isn’t just about nutrition. Natural foraging is a fundamental behavioural need, supporting mental wellbeing, reducing stress, and promoting positive welfare outcomes (Cooper & Albentosa, 2005; Henry, 2020). Horses evolved to spend 16–18 hours per day grazing and browsing (not just eating!). When we allow access to diverse plants, we don’t just support physical health, we provide positive enrichment.

By moving away from “grasses only” pastures and restoring diversity, we support metabolic health, gut function, and overall wellbeing, while also encouraging healthier, more sustainable ecosystems (Defra; Reinsch et al., 2020).

The british rewilding seed mix for UK native pony pasture, designed to increase variety of forage in a safe way for equine grazing
Wildflowers and Legumes still growing and thriving in the UK in late September.

Key Takeaways

  • Ryegrass is not poisonous, but its high NSC content makes it risky for laminitis-prone horses.

  • Laminitis usually involves an underlying condition (EMS, PPID), but sugar spikes can trigger it.

  • New medical advances (SGLT-2 inhibitors) show promise in treating acute laminitis by reducing dangerous insulin spikes.

  • Foal weaning before 12 months may predispose horses to metabolic and digestive issues. Delaying weaning and encouraging natural foraging behaviours could reduce risk.

  • Horses are not grass-only grazers — they thrive on a mix of grasses, wildflowers, legumes, and woody plants.

  • Foraging diversity = enrichment: variety in pasture improves both physical health and mental wellbeing.

  • Restriction alone isn’t enough — variety and balance are essential for horse welfare.


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