Does Short Grass Increase Laminitis Risk in Horses?

By Dr Duncan Houston

Short grass may look less dangerous than a lush green paddock, but grass height alone does not tell you whether a pasture is safe.

Recently mown grass, chronically overgrazed grass, frost-stressed grass and tall rapidly growing grass can all have very different carbohydrate concentrations. The amount the horse can eat, the part of the plant being consumed and the horse’s insulin response may matter more than the height you see from the gate.

For a horse with insulin dysregulation, equine metabolic syndrome or previous laminitis, judging pasture by height is a risky shortcut.

Quick Answer

Short grass is not automatically safer or more dangerous than tall grass.

In one small study, tall fescue mown to approximately 15 centimetres had lower soluble carbohydrate concentrations and produced a lower insulin response than grass measuring 30 to 40 centimetres. However, the study involved only six healthy geldings, the short pasture was still around six inches high, and the researchers did not investigate insulin-dysregulated horses or laminitis. (ovid.com)

Very short, overgrazed or environmentally stressed grass may expose horses to carbohydrate-rich stem bases. Tall lush grass may allow much larger bites and a greater total carbohydrate intake. For a high-risk horse, pasture height should never be used as the sole safety test.

If Your Horse Is Footsore Right Now

Remove the horse from pasture and call your veterinarian immediately if you notice:

• Short, stiff or pottery steps

• Reluctance to turn

• Strong or bounding digital pulses

• Repeated weight shifting

• Increased lying down

• Reluctance to walk on firm ground

• A rocked-back stance

• Sudden soreness affecting more than one foot

Do not force a potentially laminitic horse to walk. Place them on deep, supportive bedding, remove grain and treats, and follow your veterinarian’s instructions regarding forage, medication and hoof support.

Laminitis can begin subtly. Waiting for the dramatic rocked-back stance may mean waiting until considerable damage has already occurred.

What Are Nonstructural Carbohydrates?

Nonstructural carbohydrates, commonly shortened to NSC, are the non-fibrous carbohydrate reserves within the plant.

They include:

• Simple sugars such as glucose, fructose and sucrose

• Fructans

• Starch

Structural carbohydrates such as cellulose and hemicellulose form the plant’s fibrous framework and are important for healthy hindgut fermentation. NSC provides rapidly available or stored energy for the plant. (OSU Extension Service)

Laboratory reports may use several related measurements:

Laboratory term	What it generally includes
ESC	Simple sugars and some short-chain fructans
WSC	Simple sugars plus fructans
Starch	Plant storage carbohydrate
NSC	Usually WSC plus starch

The exact analytical method matters, so results from different laboratories should not be compared casually.

Why Does Pasture Carbohydrate Matter?

In insulin-dysregulated horses, eating carbohydrate-rich pasture can provoke an exaggerated insulin response.

Persistently or severely increased insulin can damage the laminae that suspend the coffin bone inside the hoof. This is called hyperinsulinaemia-associated laminitis and is now recognised as the most common form of laminitis in the general horse and pony population. (idppid.com)

The horse’s response matters as much as the grass.

Two horses can graze the same paddock:

• One remains clinically normal.

• One develops marked hyperinsulinaemia.

• One becomes footsore or laminitic.

This is why grass testing alone cannot determine whether a particular horse can safely graze.

Are Fructans the Main Cause of Pasture Laminitis?

Fructans are part of the pasture-carbohydrate picture, but they are not the whole explanation.

Simple sugars and starch are digested and absorbed primarily in the small intestine, increasing blood glucose and insulin. Fructans are largely fermented within the hindgut, where excessive experimental doses can disturb the microbial population and cause carbohydrate-overload laminitis.

In naturally occurring pasture-associated laminitis, the horse’s insulin response is usually the major clinical concern. Focusing only on fructan can distract from the more important questions:

• Does the horse have insulin dysregulation?

• How much pasture are they consuming?

• How high does insulin rise after grazing?

• Is the horse gaining weight?

• Have they previously had laminitis?

Grazing pasture can increase insulin within hours in susceptible ponies, even when the same exposure produces a much smaller response in metabolically normal animals. (PMC)

What Did the Grass-Height Study Actually Find?

The frequently quoted study on pasture height was published in the Journal of Equine Veterinary Science.

Researchers used:

• Six mature stock-type geldings

• A randomised crossover design

• Non-toxic endophyte tall fescue

• Ten hours of grazing each day

• Seven-day treatment periods

The two pasture treatments were:

• Short pasture: approximately 15 centimetres, or six inches

• Tall pasture: approximately 30 to 40 centimetres, or 12 to 16 inches

The short grazing areas had been mown again shortly before the horses entered them.

The study found:

• Lower NSC in the short pasture

• Lower water-soluble carbohydrates in the short pasture

• Lower ethanol-soluble carbohydrates in the short pasture

• No significant difference in pasture starch

• No significant difference in the horses’ glucose response

• A lower peak insulin concentration and insulin area under the curve while grazing the shorter pasture

Under those particular study conditions, recently mown six-inch tall fescue produced a smaller insulin response than the taller pasture. (ovid.com)

What the Study Did Not Prove

The study did not prove that all short grass is safer.

It did not include:

• Horses with insulin dysregulation

• Ponies with a previous history of laminitis

• Severely overgrazed pasture

• Grass cropped to one or two inches

• Frosted grass

• Drought-stressed grass

• Different grass species

• Naturally heterogeneous paddocks

• Laminitis as an outcome

The horses were healthy geldings with maintenance requirements. The short pasture was approximately six inches high, which is very different from a scalped or chronically overgrazed paddock.

The study therefore supports one narrow conclusion:

Under the tested conditions, recently mown six-inch tall fescue contained less soluble carbohydrate and produced a smaller insulin response than substantially taller tall fescue.

It does not provide a universal mowing prescription for metabolic horses.

Why Six-Inch Grass Is Not the Same as Overgrazed Grass

Grass measuring six inches still has considerable leaf area and available biomass.

Overgrazed pasture may be:

• Cropped almost to soil level

• Growing slowly

• Exposed to cold, drought or nutrient stress

• Producing repeated short regrowth

• Dominated by basal stems rather than leaf blades

• Mixed with weeds and bare soil

• Unable to replenish energy reserves normally

Many pasture grasses store NSC within the lower stem base close to the ground. These reserves allow the plant to regrow after grazing or mowing. Closely grazed pasture can therefore give horses greater access to carbohydrate-rich basal tissue. (OSU Extension Service)

At the same time, there may be less total grass available per mouthful.

That creates an important distinction:

• Carbohydrate concentration means the percentage of the plant made up of NSC.

• Carbohydrate intake means the total quantity the horse actually consumes.

A higher concentration does not always produce a higher total intake if very little grass is available. A lower concentration can still produce a large intake if the horse consumes many kilograms.

Short Grass vs Tall Grass

Pasture condition	Possible concern	Practical interpretation
Recently mown grass with healthy regrowth	Concentration may fall as the plant uses stored carbohydrate for growth	Not automatically safe
Very short overgrazed grass	Horses may access basal stems and stressed regrowth	Do not assume sparse means low sugar
Tall lush vegetative grass	Large bites, rapid intake and high calorie availability	High total carbohydrate intake may occur
Tall mature stemmy grass	May be less digestible and lower in some sugars	Intake and actual analysis still matter
Frosted grass	Photosynthesis may continue while growth slows	Carbohydrates may remain high
Drought-stressed grass	Growth slows while carbohydrate accumulates	Sparse-looking pasture may still be risky

The useful question is not, “Is the grass short?”

It is:

What is the horse actually eating, how much are they eating, and what happens to their insulin afterwards?

Can Tall Grass Also Be Dangerous?

Yes.

Tall lush pasture can allow horses to take large mouthfuls and consume substantial quantities very quickly. Even if the carbohydrate concentration is not unusually high, the total load may still be excessive.

Grazing behaviour changes with pasture height. Horses may favour taller areas because they can obtain more dry matter with each bite. Pasture height, density, maturity and palatability all affect intake rate. (ResearchGate)

Tall pasture also does not necessarily mean mature, stemmy or low-sugar pasture.

Grass can be both:

• Tall and rapidly growing

• Tall and leafy

• Tall and highly digestible

• Tall and rich in soluble carbohydrate

The paddock’s appearance cannot replace analysis or metabolic monitoring.

Can Short Grass Also Be Dangerous?

Yes.

Short grass becomes more concerning when it is:

• Chronically overgrazed

• Regrowing after repeated close grazing

• Drought-stressed

• Frosted

• Growing during cool sunny weather

• Nutrient deficient

• Mixed with large amounts of clover

• The only available food for a hungry horse

A very short paddock may also encourage horses to graze closer to the soil, potentially increasing the ingestion of dirt, roots, parasites and basal plant tissue.

Recent research further challenges the idea that one grass height is consistently safe. In a longitudinal study of seven native-breed ponies, both low pasture scores representing short, stressed grass and high scores representing lush pasture were associated with reduced tissue insulin sensitivity. The ponies also gained considerable weight, and the study had no ideal-weight control group, so it does not establish that either pasture condition directly caused the metabolic changes. It does show that both extremes deserve caution. (PubMed)

What Other Factors Change Grass Carbohydrate Levels?

Grass height is only one variable.

Time of Day

Grass usually produces sugars through photosynthesis during daylight.

Under warm, actively growing conditions:

• NSC is often lowest near sunrise.

• It increases through the day.

• It commonly peaks during the late afternoon or evening.

Studies commonly measure an evening increase of a few percentage points, although much larger variations can occur. (OSU Extension Service)

Cold Nights and Frost

The normal early-morning low point depends on the plant using stored energy overnight.

When temperatures are very low:

• Photosynthesis may have produced carbohydrate during the previous day.

• Cold conditions slow plant growth and carbohydrate use.

• Sugar may remain high through the night and into the following morning.

This means early-morning grazing is not automatically safe after a frost or very cold night. (OSU Extension Service)

Bright Sunlight

Bright, sunny conditions support photosynthesis and carbohydrate production.

A cool, sunny day can therefore produce substantial NSC accumulation, particularly when plant growth is limited by low temperature.

Drought

Moderate drought stress can slow growth while carbohydrate production or storage continues.

Grass may look sparse, dry or unimpressive while still containing a considerable concentration of NSC. (OSU Extension Service)

Soil Fertility

Nutrient deficiency can limit plant growth and allow carbohydrates to accumulate.

Correct fertilisation may sometimes lower carbohydrate concentration by encouraging the plant to convert stored energy into new tissue. This does not mean recently fertilised pasture is automatically safe, and fertilisation can also markedly increase the amount of grass available.

Grass Species

Cool-season grasses such as:

• Ryegrass

• Tall fescue

• Orchardgrass

• Timothy

• Bluegrass

• Brome

generally have greater potential for soluble carbohydrate accumulation than warm-season grasses such as:

• Bermudagrass

• Teff

• Crabgrass

• Millet

However, species alone cannot guarantee safety. Warm-season grasses can still exceed the appropriate carbohydrate level for a severely insulin-dysregulated horse. (OSU Extension Service)

Stage of Growth

Maturity changes the balance between leaves, stems, fibre and stored energy.

More mature grass often contains:

• More structural fibre

• Lower digestibility

• Lower protein

• A lower proportion of soluble carbohydrate

This pattern is not consistent enough to judge safety by seed heads or maturity alone.

Which Horses Are at Greatest Risk?

Pasture requires particular caution in horses and ponies with:

• Previous laminitis

• Confirmed insulin dysregulation

• Equine metabolic syndrome

• PPID accompanied by insulin dysregulation

• Obesity

• A large or firm neck crest

• Regional fat pads

• A history of unexplained foot soreness

• Rapid weight gain on pasture

• A breed or type known to be an easy keeper

Ponies, miniature horses and donkeys are often highly efficient at extracting energy from forage, but any breed can develop insulin dysregulation.

A horse does not need to be visibly obese. Lean or moderately conditioned horses can still produce an abnormal insulin response and remain at risk of laminitis. (PMC)

How Do You Know Whether a Horse Has Insulin Dysregulation?

Physical appearance can raise suspicion, but diagnosis requires veterinary testing.

Testing may include:

• Basal insulin concentration

• Oral sugar test

• Oral glucose test

• Post-feeding insulin measurement

• Testing for PPID where indicated

• Hoof radiographs when previous laminitis is suspected

A normal resting insulin result does not always exclude insulin dysregulation. Some horses appear normal until challenged with oral carbohydrate. Dynamic testing is therefore often more informative. (Merck Veterinary Manual)

Testing should be performed under controlled conditions using the veterinarian and laboratory’s current protocol. Feeding, stress, pain, recent exercise and analytical method can all affect interpretation.

Can You Test a Pasture for Sugar?

Fresh grass can be analysed, but the result is only a snapshot.

Pasture carbohydrate changes with:

• Time of day

• Weather

• Temperature

• Plant stress

• Growth stage

• Recent mowing

• Fertilisation

• The portion of plant sampled

• The height at which the sample was cut

A sample collected on one morning may not describe the pasture two afternoons later.

Pasture testing can still provide useful information, particularly when comparing fields or species, but it cannot guarantee that grazing will be safe for an insulin-dysregulated horse. Hay testing is more reliable because conserved forage changes much less from hour to hour. (OSU Extension Service)

For high-risk horses, monitoring the horse’s post-grazing insulin response may be more clinically useful than relying entirely on a pasture analysis.

How Worried Should You Be?

Low Risk

The horse:

• Has no laminitis history

• Maintains a healthy body condition

• Has no suspicious fat pads

• Has normal metabolic testing where performed

• Is grazing a well-managed pasture

• Is not rapidly gaining weight

What to do: introduce new pasture gradually, monitor condition and avoid allowing pasture to become severely overgrazed.

Moderate Risk

The horse:

• Is an easy keeper

• Is becoming cresty

• Gains weight readily

• Has unknown insulin status

• Has become mildly footsore in the past

• Is entering lush spring or autumn pasture

What to do: arrange metabolic testing, restrict pasture intake, measure weight and neck crest regularly and inspect digital pulses.

High Risk

The horse:

• Has confirmed insulin dysregulation

• Has EMS

• Has PPID with abnormal insulin

• Has previous endocrinopathic laminitis

• Has recurrent unexplained foot soreness

• Develops high post-grazing insulin concentrations

What to do: remove unrestricted pasture access. Use analysed low-NSC hay and a dry-lot or controlled-grazing plan developed with your veterinarian.

Critical

The horse:

• Is currently footsore

• Has bounding digital pulses

• Is reluctant to turn or walk

• Is repeatedly shifting weight

• Is lying down more

• Is adopting a rocked-back stance

What to do: remove the horse from pasture, minimise movement and seek emergency veterinary care.

When Is This an Emergency?

Laminitis should be treated as an emergency because the attachment between the hoof wall and coffin bone can weaken rapidly.

Call your veterinarian immediately if your horse develops:

• Sudden bilateral front-foot soreness

• Short, stilted steps

• Reluctance to walk or turn

• Strong digital pulses

• Increased hoof heat combined with lameness

• Repeated weight shifting

• A rocked-back stance

• Unusual recumbency

• Rapid deterioration after pasture access

While waiting:

1. Remove the horse from grass.

2. Place them on deep, soft bedding.

3. Do not force them to walk.

4. Remove grain, sweet feed and sugary treats.

5. Provide water.

6. Follow veterinary instructions regarding forage and medication.

7. Prepare for hoof radiographs and farriery support if recommended.

Do not repeatedly trot the horse to decide whether they are sound. That is a rather brutal diagnostic test for a structure that may already be failing.

Should You Mow Pasture for an Insulin-Dysregulated Horse?

Mowing can be useful for normal pasture maintenance, weed control and encouraging even regrowth.

It should not be used as the main medical treatment for insulin dysregulation.

The 2017 study suggests that mowing tall fescue to approximately six inches may lower soluble carbohydrate concentration under specific conditions. It does not establish that mowing to any height makes pasture safe. (ovid.com)

Repeated close mowing may:

• Stress the plants

• Reduce leaf area

• Expose lower stem tissue

• Reduce pasture health

• Encourage weeds

• Create bare soil

• Change grazing behaviour

The correct mowing and residual grazing height also differs between grass species and climate.

Use local agronomy recommendations to maintain healthy pasture. Use metabolic management to protect the horse.

The mower manages the field.

It does not diagnose the horse.

Is Early-Morning Grazing Safer?

Sometimes, but not always.

Early morning is generally the lowest-NSC period when:

• The previous night was warm enough for plant growth.

• There has been no frost.

• The grass is actively growing.

• The pasture is not severely drought-stressed.

Morning turnout may remain unsafe when:

• The night was cold.

• Frost occurred.

• The pasture is stressed.

• The horse has severe insulin dysregulation.

• The horse has recurrent laminitis.

• The grass remains rich enough to provoke marked hyperinsulinaemia.

For a genuinely high-risk horse, changing turnout from afternoon to morning may not provide enough protection.

Do Short Turnout Periods Prevent Laminitis?

Not reliably.

Horses can increase their grazing rate when they know pasture time is limited. Research has shown that horses and ponies may consume a surprisingly large proportion of their daily intake within only a few hours. Intake rate can also increase as animals learn the restricted routine. (ResearchGate)

Short turnout can reduce total intake when access is sufficiently limited, but it should not be assumed that one hour equals a tiny grass meal.

A hungry pony with sixty minutes of access can approach the paddock with the strategic focus of someone who has just discovered the buffet closes early.

Do Grazing Muzzles Work?

A well-fitted grazing muzzle can reduce pasture intake while allowing turnout, movement and social contact.

One controlled study involving four ponies found that a particular muzzle reduced dry matter intake by approximately 77% to 83% during three-hour grazing sessions. The reduction varies between studies, muzzle designs, pasture heights and individual animals. (Academia)

A muzzle is not a guarantee against laminitis.

Check that the horse can:

• Drink normally

• Graze through the opening

• Breathe comfortably

• Move the jaw freely

• Interact safely

• Wear the device without facial sores

Inspect the muzzle and horse every day for:

• Rubbing

• Hair loss

• Damaged teeth

• Enlarged openings

• Broken straps

• Weight gain or loss

• Frustration or inability to eat

• Whether the horse has learned to remove it

Long grass may bend beneath some muzzles and become difficult to access, while short upright grass can project through the opening more easily. Muzzle effectiveness therefore also changes with pasture structure. (Academia)

Are Track and Strip-Grazing Systems Better?

Track systems and controlled strip grazing can:

• Increase movement

• Separate the horse from large areas of lush grass

• Make forage intake more measurable

• Preserve social turnout

• Support weight management

Recent controlled work suggests track and strip systems can help manage horses prone to weight gain while maintaining important opportunities for movement and social behaviour. Results still depend on how much grass remains within the system and whether additional hay is correctly measured. (PMC)

Simply placing an obese pony on a grassy track does not convert the grass into salad.

The available calories still count.

What Is the Safest Pasture Plan for a High-Risk Horse?

For a horse with active laminitis, uncontrolled insulin dysregulation or repeated pasture-associated episodes, the safest initial plan is generally:

• No pasture

• A dry lot or grass-free track

• Analysed low-NSC hay

• Measured forage intake

• A suitable low-sugar ration balancer

• No grain or sugary treats

• Veterinary metabolic testing

• Appropriate hoof care

• Exercise only after the horse is sound and veterinary clearance is given

Current veterinary guidance commonly recommends forage containing less than approximately 10% NSC on a dry-matter basis for horses with EMS. Hay intake must still be sufficient to support gastrointestinal and behavioural health, even when weight loss is required. (Merck Veterinary Manual)

Some horses can later return to carefully controlled grazing after weight, hoof health and insulin response improve.

Others with severe insulin dysregulation or recurrent laminitis may never safely tolerate pasture.

How Should Pasture Be Reintroduced?

Pasture should only be reintroduced after:

• Active laminitis has resolved.

• The horse is comfortable.

• Hoof support is established.

• Body condition is improving where needed.

• Insulin dysregulation has been assessed.

• The veterinarian agrees that a trial is reasonable.

A reintroduction plan may use:

• A properly fitted grazing muzzle

• A low-biomass or controlled area

• Brief initial access

• Hay before turnout

• Careful weather selection

• Weight and neck measurements

• Daily hoof checks

• Post-grazing insulin testing

Insulin can increase markedly within several hours of grazing in susceptible ponies. Measuring the horse’s post-pasture insulin response can therefore help determine whether the current plan is genuinely controlling metabolic risk. (PMC)

Do not wait for another laminitis episode to prove that the experiment failed.

What Should You Do Next?

1. Establish the Horse’s Risk

Review:

• Previous laminitis

• Body-condition score

• Neck-crest score

• Regional fat deposits

• Breed and type

• PPID risk

• Current hoof comfort

• Recent weight change

2. Arrange Insulin Testing

Ask your veterinarian whether the horse needs:

• Basal insulin

• An oral sugar test

• An oral glucose test

• Post-feeding or post-grazing insulin

• PPID testing

3. Stop Using Grass Height as the Main Safety Test

Record the height, but also assess:

• Pasture density

• Grass species

• Weather

• Frost

• Drought

• Growth rate

• Time of day

• How much the horse is actually consuming

4. Remove High-Risk Horses From Pasture

Do not continue grazing while waiting for testing if the horse is already footsore or has recently had laminitis.

5. Analyse the Hay

Choose a low-NSC forage and feed it by weight.

6. Select a Restriction Method

Depending on risk and facilities, this may involve:

• Dry-lot turnout

• A grass-free track

• Grazing muzzle

• Strip grazing

• Space-restricted grazing

• Carefully timed access

7. Preserve Foraging Time

A horse removed from pasture still requires adequate fibre and opportunities to eat throughout the day.

Use:

• Slow feeders

• Several feeding stations

• Measured hay meals

• Safe low-energy forage where appropriate

• Social contact and movement

8. Monitor the Horse, Not Just the Paddock

Record:

• Weight

• Body condition

• Neck crest

• Digital pulses

• Hoof comfort

• Grazing time

• Muzzle use

• Pasture access

• Insulin results

Common Mistakes Horse Owners Make

Assuming Short Grass Is Safe

Sparse pasture can still contain stressed regrowth and carbohydrate-rich basal tissue.

Assuming Tall Grass Is Safe Because It Is Mature

Tall pasture may provide large bites and a very high total intake.

Believing Early Morning Is Always Low Sugar

Cold nights and frost can prevent the expected overnight reduction.

Mowing a Field and Turning the Horse Straight Back Out

One study result involving six-inch tall fescue should not be converted into a universal mowing prescription.

Relying Only on Restricted Turnout Time

Horses can increase their eating rate substantially during short grazing periods.

Treating a Grazing Muzzle as a Guarantee

Fit, pasture height, individual behaviour and muzzle condition all affect intake.

Testing the Grass but Not the Horse

A pasture result cannot reveal whether the horse’s insulin response is abnormal.

Removing Pasture but Allowing Long Periods Without Forage

Metabolic management should not create gastric, behavioural or welfare problems through prolonged fasting.

Exercising a Footsore Horse for Weight Loss

Active laminitis requires rest and hoof protection. Exercise begins only after comfort and structural stability have been assessed.

How Can Pasture-Associated Laminitis Be Prevented?

Risk reduction includes:

• Testing horses with suspicious body condition or previous laminitis

• Testing older horses for PPID where indicated

• Maintaining a healthy body weight

• Monitoring neck-crest development

• Avoiding sudden pasture access

• Introducing spring grass gradually

• Avoiding grazing after frost

• Restricting grass during high-risk seasons

• Using analysed low-NSC hay

• Maintaining appropriate pasture residual height

• Preventing chronic overgrazing

• Using muzzles or track systems where appropriate

• Keeping regular farrier appointments

• Checking digital pulses routinely

• Acting immediately when foot soreness appears

The pasture-management plan should be established before spring growth begins, not after the horse is reluctant to turn.

Can a Horse With Insulin Dysregulation Ever Graze Again?

Some can.

A carefully selected horse may return to controlled pasture after:

• Weight loss

• Improved insulin regulation

• Resolution of laminitis

• Appropriate hoof rehabilitation

• Successful post-grazing insulin monitoring

Management may still require:

• A muzzle

• Limited pasture area

• Seasonal removal from grass

• Avoidance of frost and drought stress

• Ongoing weight monitoring

• Regular metabolic testing

A horse with recurrent laminitis or severe post-grazing hyperinsulinaemia may require permanent removal from pasture.

The horse’s welfare includes friends, movement and forage, but none of those require unlimited lush grass.

FAQs About Grass Height and Laminitis

Is short grass higher in sugar than long grass?

Sometimes, but not always. Very short stressed grass may contain concentrated carbohydrates within lower stems, while one controlled tall-fescue study found lower soluble carbohydrate in recently mown six-inch grass than in 12 to 16-inch grass. Height alone cannot predict safety.

Should I mow my pasture for an insulin-resistant horse?

Do not rely on mowing as the main control method. Maintain pasture according to local agronomic recommendations, but manage the horse’s intake through dry-lot turnout, measured hay, muzzles or controlled grazing.

Is morning the safest time to graze?

Morning grass is often lower in NSC after a warm night, but not after frost or very cold conditions. Severely insulin-dysregulated horses may remain unsafe on pasture at any time of day.

Can a grazing muzzle prevent laminitis?

A muzzle can substantially reduce intake, but it does not guarantee prevention. The horse’s insulin response, total grazing time, muzzle fit, pasture condition and the amount consumed all matter.

Can pasture testing prove that my field is safe?

No. Fresh pasture changes rapidly with weather and time of day. Testing provides useful information but cannot guarantee safety for an individual insulin-dysregulated horse.

Final Thoughts

Grass height matters, but it does not provide a simple answer.

Short pasture can mean:

• Recently mown regrowth

• Severely stressed plants

• Exposed basal stems

• Reduced available biomass

• A surprisingly concentrated mouthful

Tall pasture can mean:

• Mature stemmy forage

• Lush rapidly growing grass

• Larger bites

• Greater calorie intake

• A major insulin response

The original tall-fescue study showed that recently mown six-inch pasture contained less soluble carbohydrate and produced a lower insulin response than substantially taller grass under those specific conditions.

It did not show that scalped pasture is safe, that mowing prevents laminitis or that grass height can replace metabolic testing.

For the laminitis-prone horse, the most important questions remain:

• Does the horse have insulin dysregulation?

• How much pasture are they consuming?

• How high does insulin rise after grazing?

• Is their weight increasing?

• Are their feet remaining comfortable?

Manage the horse, manage the pasture and monitor both.

The grass does not need to look dangerous to be dangerous, and it does not become safe simply because someone started the mower.

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If you are unsure whether your horse can safely graze, ASK A VET™ can help you organise their laminitis history, body condition, pasture exposure and metabolic results before you build a controlled grazing plan with your local veterinarian.