Best Time of Day To Graze Horses at Risk of Laminitis

By Dr Duncan Houston

Turnout is good for horses, but for some horses, pasture is not harmless.

A healthy, lean, active horse may tolerate grass well. An overweight pony, donkey, easy keeper, horse with equine metabolic syndrome, insulin dysregulation, PPID, or a previous laminitis episode may not. For these horses, the timing, amount, weather, grass type, and grazing method can be the difference between safe turnout and a painful laminitis flare.

The key is not simply “grass is bad” or “morning is safe.” The real issue is non-structural carbohydrate intake, which includes sugars, starches and fructans. These levels change through the day and rise under certain weather and pasture conditions.

Quick Answer

For horses at risk of laminitis, the safest grazing window is usually early morning, roughly 3 a.m. to 10 a.m., because pasture sugar levels are generally lower after the plant has used energy overnight. Avoid grazing from late morning through evening, especially on sunny days, and avoid stressed pasture after frost, drought, hard freezes or overgrazing. For very sensitive horses, there may be no completely safe grazing time, so dry lot turnout, low-NSC hay and veterinary management may be needed. (University of Minnesota Extension)

What Are Fructans and NSC?

Pasture grass contains non-structural carbohydrates, often shortened to NSC.

NSC includes:

• Simple sugars

• Starch

• Fructans

These are not the same as fibre. Fibre is the structural part of forage and is essential for normal equine gut function. NSC is the more rapidly available carbohydrate fraction that can be a problem for horses with insulin dysregulation, equine metabolic syndrome, previous laminitis or pasture-associated laminitis risk. Oregon State University Extension notes that for horses requiring a low-sugar diet, forage with less than 10 percent NSC is often used as a target, although individual recommendations should come from the veterinarian or nutritionist managing the horse.

The word “fructan” gets most of the attention, but in practice it is safer to think about total NSC intake. Rutgers explains that higher NSC intake from pasture can raise glucose and insulin responses, and in insulin-resistant horses this can worsen hyperinsulinemia enough to increase laminitis risk. (NJAES)

Why Time of Day Matters

Grass uses sunlight to make sugars during the day. Some of that energy is used for growth, and some is stored.

At night, when there is no photosynthesis, the plant uses stored carbohydrate for growth and repair. By early morning, NSC levels are usually lower. As the day progresses, sunlight drives photosynthesis again, and NSC levels rise, often peaking in the late afternoon or evening. Oregon State University Extension describes NSC as generally lowest in the morning and highest late afternoon or evening, with some studies measuring a 2 to 3 percent increase from morning to evening and others measuring larger increases.

That is why the usual advice for laminitis-prone horses is early morning grazing, not afternoon grazing.

In practice, the safest window is often:

Best option: very early morning to mid-morning
Higher risk: late morning through evening
Highest risk: sunny afternoon, early evening after a bright day, cool sunny spring or autumn days, and stressed grass

The Best Grazing Window

For many at-risk horses, the best grazing period is:

3 a.m. to 10 a.m.

University of Minnesota Extension recommends that susceptible horses graze between 3 a.m. and 10 a.m., when plant sugars are lower. Oregon State University Extension gives the same window and also advises confining horses from 10 a.m. to 10 p.m. when forage sugar content is highest. (University of Minnesota Extension)

For real yards and real humans who do not want to become nocturnal grass wardens, a practical version is:

• Turn out as early as possible

• Remove by mid-morning

• Avoid afternoon turnout for high-risk horses

• Use a muzzle if turnout is needed

• Use a dry lot or track system when pasture risk is high

The sharper clinical point is this: early morning is lower risk, not zero risk.

A horse with active laminitis, severe insulin dysregulation or repeated pasture-triggered episodes may need no grass at all until the condition is controlled.

When Pasture Is Highest Risk

Grass does not follow the clock blindly. Weather and plant stress change the risk.

Pasture is often higher risk during:

University of Minnesota Extension warns against grazing susceptible horses during drought or when temperatures fall below 40°F because plants collect sugar under stress. Oregon State University Extension also notes that cold or freezing temperatures can increase NSC, so the usual “morning is safer” pattern may not hold on chilly or frosty mornings. (University of Minnesota Extension)

This is one of the common traps: owners wait for frost to melt, then turn the horse out once the grass looks normal. The problem is not the visible frost. The problem is the plant’s stored carbohydrate after cold stress.

Which Horses Are Most at Risk?

Pasture timing matters most for horses and equids prone to laminitis or abnormal insulin responses.

Higher-risk animals include:

• Overweight horses

• Easy keepers

• Ponies

• Donkeys

• Miniature horses

• Horses with a cresty neck

• Horses with equine metabolic syndrome

• Horses with insulin dysregulation

• Horses with PPID

• Horses that have had laminitis before

• Horses gaining weight easily on grass

• Horses with limited exercise or high body condition score

University of Minnesota Extension lists overweight easy keepers, ponies, horses with metabolic syndrome and horses that have foundered before as susceptible groups. UC Davis describes equine metabolic syndrome as a disorder involving insulin dysregulation and notes that affected horses are at high risk for laminitis. (University of Minnesota Extension)

The horse that worries me most is the one that looks “fine” but is cresty, overweight, footsore after grass, and has never had insulin testing. That horse is not waiting for a dramatic warning sign. It may already be living near the edge.

Severity Guide: How Strict Should Grazing Be?

A horse with active laminitis should not be turned out on grass just because it is early morning. At that point, the question is no longer “what time should they graze?” It is “how do we stop further damage?”

When Is This an Emergency?

Laminitis should be treated as urgent.

Call your vet immediately if your horse shows:

• Reluctance to walk

• Short, pottery or hesitant steps

• Worse lameness when turning

• Heat in the feet

• Increased digital pulses

• Shifting weight from foot to foot

• Standing rocked back onto the heels

• Refusing to move

• Lying down more than usual

• Pain after recent grass access

• Sudden foot soreness in a high-risk horse

AAEP guidance states that signs of acute laminitis include lameness, heat in the feet, increased digital pulse, pain in the toe region, a hesitant “walking on eggshells” gait and a sawhorse stance. It also advises that suspected laminitis should be treated as a medical emergency and that veterinary help should be sought immediately. (AAEP)

If you suspect laminitis, remove the horse from pasture, place them on deep bedding, provide water and low-NSC forage, and call your vet. Do not keep them walking to “loosen up.” That can worsen pain and tissue damage.

What Should You Do Right Now?

1. Identify your horse’s risk level

Before changing turnout, ask:

• Has this horse had laminitis before?

• Is the horse overweight?

• Is there a cresty neck?

• Is the horse a pony, donkey, miniature, mustang or easy keeper?

• Does the horse become footsore after grass?

• Has insulin dysregulation, EMS or PPID been tested for?

• Is weight loss needed?

If the horse has a history of laminitis or metabolic disease, grazing decisions should be made with your vet, farrier and nutritionist.

2. Use early morning turnout if grazing is allowed

For many at-risk horses, use early turnout and bring them off pasture by mid-morning.

A typical plan may be:

• Turn out before sunrise or very early morning

• Remove by 9 to 10 a.m.

• Avoid afternoon and evening grazing

• Use a muzzle if intake still needs reducing

• Use a dry lot or track system when conditions are high risk

This is not a guarantee of safety, but it lowers exposure compared with afternoon pasture.

3. Do not turn out hungry

A hungry horse can eat a lot of grass very quickly.

Oregon State University Extension recommends allowing horses to fill up on low-NSC hay before turnout and not turning horses out on an empty stomach. It also advises introducing pasture slowly, starting with 15 minutes and increasing by 15 minutes every three to five days. (OSU Extension Service)

This is especially important in spring, when pasture suddenly looks tempting and horses suddenly behave like small lawnmowers with hooves.

4. Avoid stressed pasture

Do not graze high-risk horses on pasture that has been stressed by:

• Frost

• Hard freeze

• Drought

• Very cold nights

• Overgrazing

• Recent mowing

• Very short regrowth

• Lush spring flush

• Cool sunny autumn growth

Oregon State University Extension specifically warns that cold or drought-stressed grasses can be higher in NSC and that the lower stem bases of grasses store carbohydrates, making closely grazed pasture a risk.

Brown grass is not automatically safe. Short grass is not automatically safe. Frosted grass that has melted is not automatically safe. The plant’s stress history matters.

5. Use a grazing muzzle properly

A grazing muzzle can reduce intake while still allowing turnout and movement.

Useful muzzle rules:

• Introduce it gradually

• Check fit daily

• Watch for rubs

• Make sure the horse can drink

• Do not use it as a substitute for high-risk pasture control

• Monitor body weight and foot comfort

University of Minnesota Extension recommends considering grazing muzzles when grazing is important for exercise, while Oregon State recommends dry lots or muzzles when pasture NSC is high. (University of Minnesota Extension)

A muzzle is a tool, not a force field. If the grass is dangerously high risk, the better answer may be no pasture.

6. Keep pasture height sensible

Do not let at-risk horses scalp the field down to a bowling green.

Most forage species store sugars in the lower part of the plant. University of Minnesota Extension notes that the bottom 3 to 4 inches can contain high sugar, and Oregon State warns against grazing freshly cut stubble and closely grazed pastures because sugars are stored near the grass base. (University of Minnesota Extension)

The old idea that “short grass is safer because there is less of it” is often wrong. Short stressed grass can be a laminitis buffet with terrible branding.

7. Test hay and control the total diet

Pasture is only part of the diet.

For horses needing low-NSC intake, hay testing is more reliable than guessing. Oregon State University Extension states that laboratory testing is the only accurate way to determine hay NSC and that fresh pasture NSC changes quickly from morning to evening and day to day, making pasture testing less straightforward.

If your horse is high risk, the plan should include:

• Tested low-NSC hay

• Controlled hay quantity

• Balancer or mineral support where needed

• No high-sugar feeds

• No unnecessary molasses

• Careful treat control

• Weight monitoring

• Exercise when sound

The pasture schedule cannot compensate for a high-sugar total diet.

Common Mistakes Owners Make

Turning out in the evening

Evening feels cooler and kinder, but grass sugars are often higher after a sunny day. For laminitis-prone horses, evening turnout can be riskier than early morning turnout.

Waiting for frost to melt

The visible frost is not the only issue. Cold-stressed grass may retain higher NSC, and the morning low-sugar pattern may not apply after frost or freezing conditions.

Assuming short grass is safer

Short, overgrazed grass may expose the horse to sugar-rich lower stem bases and stressed regrowth.

Turning out on an empty stomach

Hungry horses can gorge quickly. Feed suitable low-NSC hay before turnout.

Relying only on a muzzle

A muzzle reduces intake, but it does not make unsafe pasture safe for every horse.

Ignoring subtle laminitis

A horse that is “a bit pottery” after grass is not being lazy. Foot soreness in an at-risk horse should be taken seriously.

Only worrying in spring

Spring is high risk, but autumn, drought, frost, cool sunny weather and stressed pasture can also be dangerous.

How To Prevent Pasture-Associated Laminitis

Prevention is built on controlling intake, timing, weight and metabolic risk.

Useful steps include:

• Test for insulin dysregulation, EMS or PPID when risk factors are present

• Keep body condition controlled

• Use early morning turnout for at-risk horses when grazing is allowed

• Avoid late afternoon and evening grazing

• Avoid grazing after frost, hard freeze or drought stress

• Use a grazing muzzle where appropriate

• Use dry lots, track systems or restricted turnout for high-risk horses

• Feed tested low-NSC hay

• Do not turn out on an empty stomach

• Avoid overgrazed pasture and very short stubble

• Introduce spring grass gradually

• Exercise regularly when the horse is sound

• Monitor digital pulses, hoof heat, stride and turning comfort

• Work with your vet and farrier after any laminitis episode

Oregon State University Extension recommends gradual pasture introduction, low-NSC hay before turnout, dry lots or muzzles when pasture NSC is high, avoiding pasture for several weeks after the first freeze in fall, and maintaining body condition around 4 to 6 out of 9. (OSU Extension Service)

Will My Horse Be Okay?

Many at-risk horses can live very well with controlled grazing, low-NSC forage, weight management, exercise and regular hoof care.

But some horses cannot safely graze freely. That is not a failure. It is good management.

The outcome depends on:

• Whether the horse has had laminitis before

• Whether insulin dysregulation is present

• Body condition

• Grass intake

• Pasture type and weather

• Hoof status

• How quickly early signs are noticed

• Whether the diet is controlled as a whole

A horse with mild risk may do well with early turnout and a muzzle. A horse with active laminitis, severe insulin dysregulation or repeated pasture-triggered episodes may need dry lot management and carefully measured low-NSC forage.

The goal is not to remove every natural behaviour. The goal is to give turnout, movement and forage in a way that does not damage the feet.

FAQs

What is the safest time of day for laminitic horses to graze?

The safest time is usually early morning, roughly 3 a.m. to 10 a.m., because pasture sugars are generally lower then. This does not apply reliably after frost, freezing temperatures, drought or other plant stress, and very sensitive horses may need no grazing at all. (University of Minnesota Extension)

Is afternoon grazing bad for horses prone to laminitis?

It can be. Grass sugars often rise through the day and peak in late afternoon or evening. For insulin-resistant or laminitis-prone horses, afternoon grazing is usually higher risk than early morning grazing.

Is frosty grass safe once the frost melts?

Not necessarily. Cold or freezing conditions can increase pasture NSC, and the usual lower-sugar morning pattern may not hold after chilly or frosty nights. Avoid grazing susceptible horses during cold-stress periods. (University of Minnesota Extension)

Can a grazing muzzle prevent laminitis?

A grazing muzzle can reduce grass intake, but it cannot guarantee prevention. It should be combined with careful timing, weight control, hoof monitoring, low-NSC forage and veterinary guidance for high-risk horses.

Should a horse with active laminitis graze?

No. A horse with active laminitis or new foot soreness should be removed from pasture and assessed by a vet. Suspected laminitis is an emergency, especially if there is heat in the feet, increased digital pulses, reluctance to move or a rocked-back stance. (AAEP)

Final Thoughts

The safest grazing time for at-risk horses is usually early morning, but timing is only one part of the picture.

Grass sugars rise and fall with sunlight, temperature, growth stage and plant stress. Late afternoon grazing, cool sunny days, frost, drought, overgrazed short grass and lush regrowth can all increase risk. For horses with insulin dysregulation, EMS or previous laminitis, pasture needs to be managed like a powerful feed, not a harmless background detail.

The practical rule is clear: graze early if grazing is allowed, avoid stressed pasture, limit intake, use low-NSC forage, monitor the feet closely and involve your vet before small warning signs become a full laminitis episode.

Pasture can be healthy. For high-risk horses, it just needs rules.

If you are unsure whether your horse is safe to graze, needs a muzzle, should be tested for insulin dysregulation, or is showing early signs of laminitis, ASK A VET™ can help you work through the signs and decide what to do next.