For many horses, pasture is one of the most natural and valuable sources of forage. But for horses that are overweight, easy keepers, insulin resistant, have Equine Metabolic Syndrome (EMS), PPID, or a history of laminitis, understanding Horse Pasture Sugar Levels can be especially important.
The old saying, “Your cheapest feed is right under your horse’s hooves,” still rings true. Good pasture provides forage, fiber, water, vitamins, minerals, and an opportunity for natural movement and grazing behavior.
The challenge is that pasture does not have a fixed nutritional profile. Sugar and other nonstructural carbohydrates (NSC) can change with the season, grass species, maturity, weather, temperature, sunlight, and time of day.
Spring and fall can be particularly important seasons for horse owners to pay attention to pasture conditions.
Grass stores carbohydrates produced through photosynthesis. During periods of active growth, plants use those carbohydrates to produce new leaves and stems.
However, when growing conditions change, the plant may accumulate more carbohydrates than it can immediately use for growth.
This is one reason pasture carbohydrate levels can change throughout the day and across the seasons.
For horses that are metabolically sensitive, consuming large amounts of NSC-rich pasture can contribute to elevated insulin responses and increase the risk of pasture-associated laminitis.
Veterinary references identify spring and periods of rapid pasture growth as important times for horses with insulin dysregulation, while fall can also become a concern when pasture growth patterns and temperatures change.
Spring pasture can be especially tempting for horses.
As temperatures rise and grass begins growing rapidly, horses may consume large quantities of fresh forage. A horse that has spent the winter eating hay can suddenly have access to much more highly palatable pasture.
For an easy keeper or metabolically sensitive horse, that sudden change can be a problem.
The risk is not simply that the grass is “green.” The important consideration is the amount and type of carbohydrate the horse is consuming.
Horses with a history of laminitis, insulin dysregulation, or EMS may need significantly restricted pasture access during periods of rapid growth. Some horses may not tolerate unrestricted pasture at all.
That short, rapidly growing grass can be particularly appealing to horses.
A horse may appear to be eating very little because the grass is short, but short pasture does not automatically mean low sugar. In fact, carbohydrate concentrations can vary considerably depending on the plant and growing conditions.
For a metabolically sensitive horse, it is better to manage pasture based on the horse, the pasture, and the conditions rather than relying only on how the grass looks.
Many horse owners become more comfortable with pasture management once the intense spring growth slows down.
But fall deserves attention, too.
Pasture carbohydrate levels can rise again during certain fall conditions, particularly when there is renewed growth following rainfall or when temperatures become cold enough to slow plant growth.
A pasture can look mature, dry, or less lush while still containing significant carbohydrates.
This is especially important following a frost.
Frost-damaged pasture can contain higher concentrations of nonstructural carbohydrates, and horses with obesity, insulin dysregulation, EMS, or previous laminitis may be particularly vulnerable. University of Minnesota Extension recommends additional caution following a killing frost.
One of the most important things to understand about pasture sugar is that it is not constant throughout the day.
Plants produce carbohydrates through photosynthesis when exposed to sunlight. Pasture NSC levels generally tend to increase during daylight hours and can be higher later in the day than early in the morning.
Overnight, plants continue using stored carbohydrates for their own metabolism and growth.
However, cold nights can change this pattern.
When temperatures are low, especially when plant growth slows or the grass experiences frost, the plant may not use carbohydrates as quickly. This can leave more carbohydrate stored in the plant.
That means the old rule of simply turning a metabolically sensitive horse out at night is not appropriate for every situation.
The weather matters.
Veterinary guidance notes that early-morning grazing may be preferable during periods when pasture NSC is elevated, but cold-weather and frost conditions require additional caution.
A pasture does not have to look lush and green to contain significant sugar.
Drought, heat, cold temperatures, and limited growth can all affect how much carbohydrate the plant is able to use.
This is why you cannot reliably determine the NSC content of grass simply by looking at it.
The same is true of hay.
Are you managing a horse that is particularly sensitive to sugar and starch? Having hay tested can provide much more useful information than judging the hay by appearance.
Our recent article, Understanding NSC in Horse Supplements: Sugar, Starch & Metabolic Health, explains why the entire diet—not just one feed or supplement—should be considered when managing NSC.
Every horse is an individual, but extra caution may be appropriate for horses that are:
A horse with a previous episode of laminitis should not simply be turned out on lush pasture because it appears to be “doing better.”
Pasture access should be discussed with your veterinarian when metabolic disease or previous laminitis is involved.
There is no single pasture-management strategy that works for every horse. The goal is to control the amount of pasture carbohydrate your horse consumes while still providing appropriate forage and nutrition.
Do not suddenly turn a horse from a winter hay diet onto unlimited spring pasture.
Gradually increasing turnout gives you an opportunity to monitor how your horse responds to the change.
For a horse with a history of laminitis or metabolic disease, work with your veterinarian or equine nutrition professional to establish an appropriate turnout plan.
Providing hay before turnout can help prevent a horse from rushing out onto pasture and consuming large amounts of grass immediately.
For horses requiring carbohydrate restriction, the hay itself should also be selected carefully and, when appropriate, tested for NSC.
For a metabolically sensitive horse, limiting the amount of time spent grazing can be an important management tool.
The safest turnout schedule is not necessarily the same every day.
Consider:
For horses with insulin dysregulation, AAEP guidance specifically discusses restricted turnout, dry lots, and grazing muzzles as tools for limiting pasture carbohydrate intake.
Proper pasture management can help maintain healthy forage and reduce overgrazing.
Avoid allowing horses to continuously graze pasture down to very short stubble. Rotate or rest pastures when possible, and maintain good pasture health through appropriate mowing, manure management, and other local pasture-management practices.
Regular mowing can also help with weed control and pasture utilization.
Regular, appropriate exercise is an important part of maintaining a healthy body condition and supporting metabolic health.
For a horse that is overweight or insulin dysregulated, exercise should be appropriate for the horse’s physical condition and any existing hoof or soundness problems.
If a horse is actively laminitic, exercise decisions should be made with veterinary guidance.
Pasture is only one part of the horse’s nutritional program.
Hay, pasture, concentrates, ration balancers, supplements, treats, and other feeds all contribute to the overall diet.
For horses that are sensitive to dietary sugar and starch, it is important to consider the total NSC intake, rather than focusing on one ingredient or one product.
It is also important not to confuse carbohydrate management with eliminating essential nutrients.
A horse still needs appropriate vitamins, minerals, amino acids, protein, fiber, water, and other nutrients.
Forage analysis can be especially helpful when you are trying to determine whether your horse’s hay or pasture is meeting those nutritional needs.
At Equine Challenge Supplements, we believe nutrition should begin with understanding the forage being fed.
Different types of forage can have different nutritional profiles, which is why we offer forage-specific vitamin and mineral supplementation for horses consuming grass and alfalfa-based diets.
A properly selected ration balancer or vitamin and mineral supplement can help fill nutritional gaps while being fed at a relatively small daily amount.
You can learn more about our Grass Ration Balancers and forage-specific vitamin and mineral supplements here.
Understanding horse pasture sugar levels does not mean that every horse needs to be removed from pasture.
Healthy horses can benefit greatly from access to quality pasture.
The important point is that pasture changes.
Spring growth, fall growth, cold nights, frost, rainfall, drought, sunlight, grass maturity, and the individual horse can all influence how pasture should be managed.
If your horse is overweight, an easy keeper, insulin dysregulated, diagnosed with EMS or PPID, or has a history of laminitis, paying closer attention to pasture conditions can be an important part of protecting your horse’s health. Understanding how grass grows, and how sugars are used and available in grass can help you better manage your overweight, easy keeper and at-risk horses. High sugars in grass and hay can be dangerous for horses prone to certain problems, so keep an eye on the weather, grass growth, and the weight of the horse. If after all these precautions your horse does suffer from laminitis or founder, consider helping the recovery of your horse with Laminae 911 herbal support.
When in doubt, work with your veterinarian or qualified equine nutrition professional and consider having your forage tested.
Know your grass. Know your horse. And remember that what is growing under your horse’s feet is part of the diet, too.
Spring pasture can contain significant amounts of nonstructural carbohydrates, particularly during periods of rapid growth. The actual level varies with grass species, weather, maturity, sunlight, and other growing conditions.
Fall pasture can also become a concern, particularly following rainfall and during periods when temperatures change rapidly. Frost and cold temperatures can also affect pasture carbohydrate levels.
Pasture NSC generally changes throughout the day, often increasing during daylight and reaching higher levels later in the day. Early morning grazing is commonly recommended as a lower-risk period for some metabolically sensitive horses, but cold nights and frost can change the situation.
No. Nighttime turnout is not automatically safer. Cold nights can cause pasture plants to retain more carbohydrates, so temperature and pasture conditions should be considered along with the time of day.
Some horses with a history of laminitis may tolerate carefully restricted pasture, while others may not. Horses with insulin dysregulation or recurrent laminitis can require very strict pasture restriction. Discuss an appropriate grazing plan with your veterinarian.
Not necessarily. Grass carbohydrate levels depend on much more than grass height. Short, stressed, or slow-growing pasture can still contain significant carbohydrates.
No. Appearance alone cannot reliably determine pasture NSC. If your horse requires carbohydrate restriction, forage testing can provide more useful information.
Feeding hay before turnout can help slow the horse’s initial pasture consumption. For horses requiring a low-NSC diet, the hay should also be evaluated for its carbohydrate content.
Pasture can be a significant source of sugars, starches, and fructans. For horses with insulin dysregulation, controlling pasture intake can be an important part of reducing dietary carbohydrate exposure and managing laminitis risk.
Yes. Restricting calories or dietary sugar does not eliminate the horse’s need for essential vitamins and minerals. A forage-specific ration balancer or concentrated vitamin and mineral supplement can provide targeted nutrition without requiring large amounts of feed.
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