Grass looks like the most natural food in the world for a horse — and it is.
But there is a problem that many horse owners don't realise:
Grass can contain a surprising amount of sugar.
For some horses, particularly easy keepers, overweight horses and those prone to laminitis or metabolic problems, eating large amounts of high-sugar grass can cause significant problems.
The issue isn't simply that grass contains sugar. All grass contains sugar and horses need carbohydrates for energy.
The problem is when a horse is consuming more readily available carbohydrate than their body can comfortably handle.
This is particularly important during periods of rapid grass growth, when pasture can contain high levels of non-structural carbohydrates (NSC). NSC includes sugars, starches and fructans. The amount in pasture can vary considerably depending on the grass, season, weather, time of day and growing conditions.
Why Is Spring Grass Such a Problem?
Spring is often the time when horse owners notice problems appearing.
The grass suddenly starts growing rapidly, and it looks lush, green and nutritious.
But rapidly growing grass can contain significant amounts of readily available carbohydrate.
The same thing can happen in autumn when warm days are combined with cool nights. Grass can continue photosynthesising during the day while cooler conditions slow its growth, allowing sugars and other NSC to accumulate in the plant.
Drought-stressed or cold-stressed pasture can also contain elevated NSC levels. In some circumstances, pasture can contain considerably more NSC than grass growing rapidly under favourable conditions.
This is why a horse that has been perfectly fine on the same paddock for months can suddenly develop problems when the weather changes.
What Does Sugar Do to the Horse?
When a horse eats carbohydrate, the body breaks it down and uses it for energy.
In a healthy horse, blood glucose and insulin rise after eating and then return towards normal.
However, some horses don't regulate insulin normally. These horses may be insulin dysregulated and can be particularly sensitive to diets containing large amounts of sugar and starch.
Repeated exposure to high-NSC pasture can contribute to excessive insulin responses in susceptible horses. High insulin levels are strongly associated with pasture-associated laminitis in insulin-dysregulated horses.
This is why a horse doesn't necessarily have to be eating grain to have a high-sugar diet.
A horse can consume a lot of sugar simply by eating large amounts of lush pasture.
Which Horses Are Most at Risk?
Some horses seem to cope with almost anything they eat, while others become overweight or foot-sore very easily.
Pay particular attention to horses that:
- Gain weight very easily
- Are described as "good doers"
- Have a cresty neck
- Develop fat deposits around the shoulders or tailhead
- Have previously had laminitis
- Have insulin dysregulation or EMS
- Become footy or sensitive after eating grass
- Have a strong appetite and seem constantly hungry
- Struggle to maintain a healthy weight despite restricted feed
- Become lethargic or change behaviour when pasture changes
A horse doesn't have to be extremely overweight to have a problem with carbohydrate metabolism.
Why Short Grass Can Be Particularly Problematic
Many people assume that short grass is safer because there isn't much to eat.
Unfortunately, this isn't necessarily the case.
When grass is repeatedly grazed or mown, the plant needs to use its stored carbohydrate reserves to produce new growth. A significant amount of NSC is stored in the lower parts of the plant, particularly around the stem base.
This means that short, actively growing pasture isn't necessarily low in sugar.
And because horses are selective grazers, they can consume a considerable amount of the most palatable parts of the pasture.
It's Not Just About the Grass
Grass isn't the only source of sugar and starch in a horse's diet.
Concentrated feeds can add significantly to the overall carbohydrate load.
This includes:
- Oats
- Barley
- Corn
- Wheat
- Molasses
- Sweet feeds
- Some commercial feeds
- High-sugar treats
A horse eating high-sugar grass and then receiving grain or sweet feed on top of it may be consuming considerably more carbohydrate than they actually require.
For many horses, particularly those in light work, good-quality forage and a balanced vitamin and mineral supplement may provide everything they need without the need for large amounts of hard feed.
How Can You Reduce Sugar Intake?
The good news is that there are many practical ways to reduce the amount of sugar your horse consumes.
You don't necessarily have to remove every blade of grass.
The best approach depends on the individual horse and how sensitive they are.
1. Provide Plenty of Suitable Hay
Forage should remain the foundation of the diet.
For horses that are sensitive to sugar, choose a mature, fibrous hay that is relatively low in NSC where possible.
If you have access to hay testing, this is the most reliable way to find out what you are actually feeding.
You cannot reliably determine sugar levels simply by looking at a bale of hay. Two hays that look almost identical can have very different carbohydrate levels.
2. Soak Hay When Necessary
If suitable low-NSC hay isn't available, soaking can be used to reduce the water-soluble carbohydrate content.
Soaking hay in water allows some of the soluble sugars to leach into the water.
A soaking period of around 15–60 minutes can reduce water-soluble carbohydrates, although the amount removed varies between hays.
After soaking:
Discard the water and feed the hay promptly.
Don't assume that soaking always makes high-sugar hay "safe". If a horse is particularly sensitive, testing the hay before and after soaking is the best way to know what you are actually feeding.
3. Manage Pasture Access
If your horse is prone to laminitis or metabolic problems, unrestricted access to lush pasture may not be appropriate.
Depending on the individual horse, options can include:
- Restricting grazing time
- Using a grazing muzzle
- Providing a dry lot or sacrifice area
- Offering low-NSC hay while limiting pasture
- Increasing access to mature, less actively growing pasture
- Avoiding periods when pasture NSC is likely to be particularly high
Grazing muzzles can significantly reduce the amount of grass a horse consumes while still allowing some access to pasture.
4. Think About When Your Horse Is Grazing
The amount of sugar in grass changes throughout the day.
Grass produces sugars through photosynthesis when exposed to sunlight. Under certain conditions, particularly when growth is slowed by cool temperatures, sugars can accumulate.
For horses that are particularly sensitive, grazing during periods when pasture NSC is likely to be lower may help reduce intake.
However, there is no single "safe time" that applies to every paddock or every day because weather and growing conditions make such predictions unreliable.
If your horse is highly susceptible to laminitis, pasture testing and careful management are safer than relying solely on the time of day.
5. Don't Forget Exercise
Exercise is an important part of keeping a horse metabolically healthy.
Regular movement helps the horse use glucose for energy and can help maintain a healthy body condition.
This is particularly important for horses that are easy keepers.
Of course, exercise isn't appropriate for a horse experiencing active laminitis or significant foot pain. In those situations, appropriate veterinary and hoof-care advice is important.
6. Keep Hard Feed Simple
If your horse is already getting plenty of energy from pasture, they may not need large amounts of grain or concentrate feed.
Instead, keep hard feed as simple as possible and use it primarily as a carrier for the vitamins, minerals or other nutritional support the individual horse requires.
Remember:
Grass + grain + molasses + sugary treats can quickly add up.
What About Minerals?
Sugar isn't the only consideration when feeding pasture.
Fast-growing grasses can also have an unusual mineral profile, and the mineral content of pasture depends heavily on soil, grass species, growing conditions and fertilisation.
This is why a good-quality vitamin and mineral supplement can be particularly useful when the horse's diet consists largely of pasture and hay.
The aim isn't to "counteract" sugar with one particular mineral.
Instead, the goal is to provide a balanced diet that supports normal metabolism, healthy hooves and good digestive function.
How Do You Know If Your Horse Is Getting Too Much Sugar?
Watch your horse closely when pasture changes.
Signs that your horse may not be coping well with the amount of grass they are eating can include:
- Weight gain
- A rapidly developing cresty neck
- Fat deposits around the tailhead or shoulders
- Foot sore or reluctance to walk on hard ground
- Increased sensitivity in the feet
- Recurrent laminitis
- Changes in behaviour
- Excessive appetite
- Difficulty maintaining a healthy body condition
If your horse develops sudden or significant foot pain, heat in the feet, a strong digital pulse or other signs suggestive of laminitis, treat this as an urgent problem and seek veterinary assistance.
The Good News About Grass
The answer isn't necessarily to keep every horse off grass forever.
Many horses can enjoy pasture without problems.
The important thing is understanding that not all grass is the same.
The sugar content of pasture can change dramatically depending on:
- Grass species
- Season
- Weather
- Temperature
- Sunlight
- Rainfall
- Drought
- Stage of growth
- Grazing pressure
- Time of day
For horses that are metabolically sensitive, learning to manage these variables can make a huge difference.
The Greenpet Approach
At Greenpet, we believe the foundation of feeding a horse is fibre first.
Rather than simply adding more and more feeds and supplements, look at the whole diet.
Ask yourself:
How much grass is my horse eating?
How much sugar and starch are they consuming?
Are they getting enough mature, fibrous forage?
Do they actually need the hard feed they're receiving?
Are they getting enough exercise for the amount of energy they're consuming?
Are their vitamins and minerals balanced?
For a horse that is struggling with sugar, the answer is often not another supplement or another feed.
Sometimes the most important change is simply reducing the amount of high-sugar grass going into the horse and replacing it with appropriate, low-sugar fibre.
A horse's digestive system was designed for a diet based predominantly on forage.
Feed the fibre. Manage the sugar. Keep them moving. And don't wait for sore feet before you take action.
For more advice, complete our complimentary Horse Questionnaire.