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Does Ryegrass Cause Laminitis? What Every Horse Owner Needs to Know

  • Sep 23, 2025
  • 9 min read

Updated: Jun 30

The short answer is no. Ryegrass isn't poisonous and it doesn't directly cause laminitis. However, modern ryegrass dominated pastures can create grazing conditions that increase laminitis risk in susceptible horses.


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 ryegrass or sugar themselves. In most pasture associated cases, elevated insulin concentrations are the biological mechanism that damages the lamellae.


High intakes of non-structural carbohydrates (NSCs), including those from ryegrass-dominated pasture, can increase laminitis risk because they may drive excessive insulin responses, particularly in susceptible horses.


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

Type 1: Sepsis/SIRS-related laminitis

Linked to systemic inflammation, often caused by bacteria.

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

Pasture associated laminitis refers to cases where grazing contributes to excessive insulin responses. High non-structural carbohydrate (NSC) intake from the diet triggers underlying endocrine dysfunction or insulin dysregulation.

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 may or may not already have an impaired metabolic system, but high-sugar and starch intake pushes insulin levels up so that insulin becomes dysregulated (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) can also increase risks of colic, hindgut acidosis, and gastric ulcers (Colombino et al., 2022; Smarsh & Orr, 2024). Horses evolved to consume a wide variety of predominantly fibrous plants over many hours each day. Modern improved pasture, particularly when dominated by productive grass species, can provide a very different nutritional environment.


Ryegrass: Why the Concern?

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

It was bred for dairy farming, where high energy = 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 insulin dysregulation in our horses.

Means fewer alternative plants for horses to select from that are typically lower in sugar and starch.

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 Evolved to Eat in Natural Grazing

When we picture horse pastures, we tend to think only of lush green grass, but this 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 20-60% of the natural forage available; providing protein, vitamins, and minerals which can act as beneficial secondary compounds (Defra Grass & Forage Science study; Jefferson, 2005; Reinsch et al., 2020).


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

Typical domestic management alters this natural diet diversity.


Weaning and Early care may also play a role.


Recent studies (Proudman et al., 2024) show that early weaning influences the development of the gut microbiome.


Although more research is needed to understand the long-term implications for foraging behaviour and metabolic health, early weaning may influence future forage preferences. Foals weaned before 12 months may consume more sugary grass than nutrient-rich milk and may have fewer opportunities to learn browsing and plant selection behaviours from older horses, which could have long-term implications for health (Tavenner, 2020).


Keeping foals with their dams longer and giving domestic horses more access to fresh, diverse forage may help horses to better learn to self-select what they eat and even learn to chose from a wider range of plants (Neto, 2012). It is also possible that young horses learn aspects of plant selection from older herd members. Some researchers have suggested this may contribute to behaviours studied under the field of zoopharmacognosy, where animals appear to select plants that influence their health.

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 and starch intake, and is necessary at times, 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.

One of the biggest misconceptions in equine pasture management is that preventing laminitis simply means restricting grass. In reality, it's about understanding the grazing ecosystem as a whole. Grass species, plant diversity, soil health, grazing management, horse metabolism and individual susceptibility all interact. The healthiest grazing systems don't rely on one "safe" plant species. They rely on appropriate grass species, diverse forage, healthy soils and management that matches the needs of the individual horse.


Key Takeaways

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

  • Laminitis usually involves dysregulated insulin levels. High sugar and starch in the diet can trigger this, even more so when there is an underlying endocrine condition (i.e. EMS, PPID).

  • 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 — Restriction may sometimes be necessary, particularly during acute risk periods, but long term management should also consider pasture composition, grazing management, horse metabolism and opportunities for safe dietary diversity.


Frequently Asked Questions


Does ryegrass cause laminitis?


Ryegrass does not directly cause laminitis, and it is not poisonous to horses. However, modern perennial ryegrass varieties have been bred for agricultural productivity and can contain higher levels of non-structural carbohydrates (NSCs) than many traditional meadow grasses. In horses that are insulin dysregulated or have conditions such as Equine Metabolic Syndrome (EMS) or PPID, grazing high-NSC pasture can increase the risk of endocrinopathic laminitis.


The risk depends on the whole grazing system, including the horse's metabolic health, the amount and type of grass available, pasture management, weather conditions and the overall diversity of the sward.


Is long grass safer than short grass?


Not necessarily. Grass height alone doesn't determine how much sugar it contains. Young, rapidly growing grass can contain high levels of non-structural carbohydrates, but stressed short grass can also accumulate sugars under certain environmental conditions.


Rather than focusing solely on grass height, it's more helpful to consider the condition of the pasture, how stressed individual plants are, the grass species present, weather patterns, grazing pressure and your horse's individual risk factors. A well-managed, species-diverse pasture is often a more useful goal than simply aiming for long or short grass.


What grass is safest for laminitis-prone horses?


There isn't one single "safe" grass species. Traditional meadow grasses such as red fescue, crested dog's-tail, common bent and sweet vernal grass are generally lower in non-structural carbohydrates than highly productive ryegrass varieties, but sugar content varies with weather, season, plant growth stage and management.


The overall composition of the pasture is often more important than any individual grass species. A diverse grazing sward containing a range of appropriate grasses, herbs and wildflowers can help reduce reliance on a single high-sugar forage source while supporting more natural grazing behaviour.


Can wildflowers help horses prone to laminitis?


Wildflowers are not a treatment for laminitis, and simply adding wildflowers will not make a high-risk pasture safe. However, carefully selected horse-safe wildflowers and herbs can increase plant diversity, provide opportunities for more varied foraging behaviour and gradually help create a more balanced grazing ecosystem.


For horses with laminitis or insulin dysregulation, pasture management should always be tailored to the individual horse, taking veterinary and nutritional advice into account where appropriate.


Should horses with laminitis avoid grass completely?


Not always. During an acute laminitis episode or periods of very high pasture risk, temporary removal from grazing may be necessary to protect the horse. However, long-term management depends on the individual horse, the severity of insulin dysregulation, pasture conditions and the wider management system.


The goal isn't simply to avoid grass forever. It's to create a grazing system that supports metabolic health through appropriate pasture composition, careful grazing management, regular monitoring and, where necessary, targeted dietary management.


References


 
 
 

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