Do High-Starch Feeds Cause Inflammation in Horses?

Do High-Starch Feeds Cause Inflammation in Horses?

By Dr Duncan Houston

High-starch feeds are not automatically “bad” for every horse.

That matters, because some horses genuinely need extra calories for growth, pregnancy, lactation, heavy training, or competition. The problem is when starch is fed to the wrong horse, in the wrong amount, in meals that are too large, or in horses already at risk of obesity, insulin dysregulation, PPID, colic, ulcers, or laminitis.

In those horses, high-starch feeding can become more than a calorie issue. It can affect insulin, gut health, inflammatory markers, and hoof risk.

Quick Answer

High-starch meals can increase inflammatory markers in horses, especially older and overweight horses. A study from Sam Houston State University found that older and heavier-conditioned horses developed a quicker post-meal rise in interleukin-1β, also called IL-1β, after high-NSC feeding compared with younger, leaner horses. (MDPI)

That does not mean one grain meal will ruin every horse. It means high-starch feeds should be used carefully, especially in horses that are overweight, senior, laminitis-prone, insulin-dysregulated, or not in heavy work.

What Are High-Starch Feeds?

Starch is a type of non-structural carbohydrate, or NSC. In simple terms, NSCs are the more rapidly available carbohydrate fractions in the diet, including starches and sugars.

Common high-starch or high-NSC feeds include:

• Corn

• Oats

• Barley

• Sweet feeds

• Molasses-heavy feeds

• Many traditional grain concentrates

• Some high-energy performance feeds

• Some senior feeds, depending on the formula

This is why the label matters. “Senior,” “maintenance,” “complete,” or “conditioning” does not automatically mean low-starch.

In practice, I care less about the marketing name on the bag and more about the actual starch, sugar, NSC, calories, fibre, fat, feeding rate, and the horse standing in front of me.

What Did the High-Starch Inflammation Study Find?

A 2021 study looked at how age and body condition affected the IL-1β response after horses consumed high-NSC meals. The diet used steam-rolled barley to provide 1.2 g of NSC per kg of body weight. (MDPI)

The key findings were:

• Overweight horses had a post-meal IL-1β rise early.

• Leaner horses did not show the same immediate response, but IL-1β increased after 14 days of daily high-NSC feeding.

• Older horses had a stronger post-meal IL-1β response compared with middle-aged horses after the high-NSC feeding period.

• The authors concluded that older and heavier-conditioned horses appear to have a more immediate inflammatory response to NSC consumption. (MDPI)

That is useful, but it needs careful interpretation.

This study does not prove that high-starch feeds directly cause every inflammatory disease in horses. It does not prove that starch causes arthritis, Cushing’s disease, colic, or laminitis by itself.

What it does show is more practical:

Older and overweight horses appear less tolerant of high-NSC meals from an inflammatory-marker standpoint. That is exactly the type of horse where I would be more cautious with grain, sweet feed, barley, corn, and high-starch concentrates.

What Is IL-1β and Why Does It Matter?

IL-1β is a pro-inflammatory cytokine. In plain English, it is one of the chemical messengers involved in inflammation.

A rise in IL-1β does not mean a horse is definitely sick. It does mean the body has produced a measurable inflammatory signal after feeding.

That distinction matters.

The problem with over-simplified nutrition advice is that it jumps from “this marker increased” to “this feed causes disease.” Real medicine is messier than that. The better conclusion is that high-starch feeding may be more inflammatory in certain horses, especially older or overweight horses, and that should influence how we feed them.

Why Older and Overweight Horses Are Higher Risk

Older horses and overweight horses often have less metabolic spare room.

Some are insulin dysregulated. Some have equine metabolic syndrome. Some have PPID, also called Cushing’s disease. Some are simply over-conditioned and carrying more inflammatory fat tissue than they should.

UC Davis describes equine metabolic syndrome as a disorder associated with insulin dysregulation, regional fat deposition, difficulty losing weight, and a high risk of laminitis. Management is mainly based around diet, exercise, NSC restriction, calorie control, and reduction or elimination of pasture access when needed. (Center for Equine Health)

That is why high-starch feeding is not just a “grain versus no grain” debate.

The real question is:

Can this individual horse safely handle this amount of starch, in this meal size, with this workload, this body condition, and this laminitis risk?

For many overweight, cresty-necked, senior, insulin-dysregulated, or laminitis-prone horses, the answer is often no.

Why Too Much Starch Can Affect the Gut

Horses are designed to eat fibre for many hours a day. Their digestive system is not built around large, fast meals of cereal grain.

When starch intake is too high, especially in large meals, the small intestine may not digest all of it before it reaches the hindgut. Once excess starch reaches the hindgut, it can disrupt fermentation, alter bacteria, increase acid production, and increase the risk of digestive upset.

Merck Veterinary Manual notes that feeding more than 50% of the ration dry matter as high-starch or high-sugar concentrates increases the risk of laminitis, colic, and equine gastric ulcer syndrome. It also advises that horses should not receive more than 0.5% of body weight in grain-based concentrates in one meal, because larger meals increase the risk of laminitis and digestive upset. (Merck Veterinary Manual)

This is where many feeding problems start.

Not with one single ingredient being evil.

With meal size, horse risk, workload, body condition, and a ration that has drifted too far away from fibre.

Does High Starch Cause Laminitis?

High starch can contribute to laminitis risk, but the pathway depends on the horse and situation.

In grain overload, excessive concentrate consumption can allow undigested starch to pass into the hindgut. Merck explains that this can lead to rapid fermentation, lactic acid production, bacterial disruption, toxin absorption, endotoxaemia, and systemic inflammation. (Merck Veterinary Manual)

In metabolic horses, the issue is often insulin dysregulation. Horses with obesity, EMS, PPID, or insulin resistance can be predisposed to laminitis, especially when exposed to high-carbohydrate feeds or pasture. (Center for Equine Health)

So yes, high-starch feeding can be part of the laminitis picture.

But the risk is not equal in every horse. A fit racehorse in heavy work is not the same as a cresty-necked pony on lush pasture. Same species. Very different metabolic chaos potential.

Risk Framework: How Worried Should You Be?

Low Risk

This is usually lower risk if your horse:

• Is lean and fit

• Has no history of laminitis

• Has no cresty neck or abnormal fat pads

• Has no known insulin dysregulation

• Is in genuine moderate to heavy work

• Eats mostly forage

• Receives small, weighed concentrate meals

• Has normal manure, appetite, hoof comfort, and performance

These horses may tolerate some starch well, especially if the diet is balanced and matched to workload.

Moderate Risk

This is more concerning if your horse:

• Is gaining weight

• Is older

• Is lightly worked

• Has a mild cresty neck

• Gets sweet feed or grain daily despite low workload

• Has intermittent loose manure or mild colic episodes

• Gets large concentrate meals once or twice daily

• Has not had hay, pasture, or feed NSC checked

This is the stage where the diet should be reviewed before a bigger problem appears.

High Risk

This is high risk if your horse:

• Is overweight or obese

• Has a strong cresty neck

• Has regional fat pads

• Has equine metabolic syndrome

• Has insulin dysregulation

• Has PPID and insulin resistance

• Has had laminitis before

• Becomes footsore after pasture or feed changes

• Is eating high-starch feed despite low exercise

These horses usually need a low-NSC, forage-first plan and veterinary input.

Critical

This is urgent if your horse:

• Breaks into the feed room and eats a large amount of grain

• Develops colic signs after a feed change or grain overload

• Develops diarrhoea after grain access

• Becomes suddenly lame or pottery

• Has heat in the feet

• Has strong digital pulses

• Rocks back onto the hindlimbs

• Refuses to walk normally

• Is depressed, sweaty, painful, or off feed

This is not a “switch to low-starch feed next week” problem. This is a call-the-vet-now problem.

When Is This an Emergency?

High-starch feeding becomes an emergency when it causes or may cause grain overload, colic, diarrhoea, endotoxaemia, or laminitis.

Call a vet urgently if your horse has:

• Accessed a large amount of grain or concentrate

• Pawing, rolling, flank-watching, sweating, or repeated lying down

• Diarrhoea after a feed accident

• Depression or refusal to eat

• Elevated heart rate

• Fever

• Stiffness or reluctance to move

• Heat in the hooves

• Strong digital pulses

• A rocked-back laminitis stance

• Sudden lameness after pasture or feed changes

Merck describes laminitis as one of the most important and catastrophic diseases in horses, with causes including carbohydrate overload, endotoxaemia, and endocrine disease. The hallmark clinical sign includes severe lameness with bounding digital pulses. (Merck Veterinary Manual)

Do not wait for the horse to look “really bad.” Grain overload and laminitis risk can develop before the horse looks dramatic.

What Else Can Look Like Feed-Related Inflammation?

Not every stiff, sore, overweight, or dull horse has a starch problem.

Important rule-outs include:

• Equine metabolic syndrome

• PPID

• Insulin dysregulation

• Laminitis

• Gastric ulcers

• Hindgut disturbance

• Dental disease

• Poor-quality hay

• Excess calories from pasture

• Low protein intake

• Vitamin or mineral imbalance

• Joint disease

• Chronic pain

• Poor fitness

• Liver or kidney disease

• Parasite burden

• Chronic infection

• Inadequate exercise

• Overfeeding oil or calorie-dense feeds

This is why a proper diet review is more than saying “remove grain.”

A thin senior horse struggling to maintain weight needs a different plan from an obese pony with laminitis. Both may need low-starch feeding, but the calorie strategy will be different.

What Should You Do Next?

1. Do Not Suddenly Remove Everything

Sudden feed changes can upset the gut.

Unless there is an emergency, change the diet gradually over 7 to 14 days. If the horse has laminitis, colic, diarrhoea, or suspected grain overload, speak to a vet immediately rather than trying to redesign the diet yourself.

2. Weigh the Feed

Scoops lie. Scales do not.

Weigh the concentrate, hay, balancers, beet pulp, rice bran, chaff, and supplements. Many feeding problems happen because owners feed by habit, not by actual weight.

3. Check the Label

Look for:

• Starch

• Sugar

• NSC

• Digestible energy

• Fibre

• Fat

• Feeding rate

• Whether it is a complete feed or concentrate

• Whether it is suitable for metabolic horses

If the label does not show starch or NSC, contact the manufacturer or choose a feed that gives you clearer information.

4. Test the Hay if the Horse Is Metabolic

For horses with EMS, insulin dysregulation, laminitis risk, or obesity, forage testing is extremely useful. UC Davis notes that feed analysis can determine NSC content and that hay for EMS horses should ideally be under 10% NSC on a dry matter basis. (Center for Equine Health)

Guessing hay sugar is a dangerous little farm hobby.

5. Reduce Starch Before You Add Supplements

The first solution is usually not turmeric, magnesium, cinnamon, or a miracle inflammation powder.

The first solution is often:

• Less starch

• Less sugar

• Better forage control

• Correct calories

• Proper minerals

• More movement if sound

• Veterinary testing when needed

Supplements cannot outsmart a diet that is wrong for the horse.

6. Replace Calories Sensibly

For older horses or poor doers, removing starch does not mean starving them.

Safer calorie options may include:

• Molasses-free beet pulp

• Low-starch complete feeds

• Low-NSC senior feeds

• Forage cubes or pellets

• Higher-fat feeds where appropriate

• Vegetable oil or stabilised fat sources, introduced slowly

• Balanced ration balancers

• Higher-quality forage if suitable

Merck notes that beet pulp is low in starch and sugar, while oils and fats can increase energy density if introduced gradually. (Merck Veterinary Manual)

7. Feed Smaller Meals

If concentrates are needed, split them into smaller meals.

Large grain meals are where risk increases. Merck advises avoiding more than 0.5% of body weight in grain-based concentrates in a single feeding and recommends dividing larger daily concentrate amounts into smaller meals at least four hours apart. (Merck Veterinary Manual)

For a 500 kg horse, 0.5% body weight is 2.5 kg of grain-based concentrate in one meal. Many horses should receive far less than this, especially if they are not in hard work or have metabolic risk.

8. Match Feed to Workload

A horse in light work does not need to be fed like a racehorse.

If the horse is not losing weight, not in hard work, and not pregnant, lactating, growing, or struggling to maintain condition, high-starch concentrate may not be needed at all.

For many horses, good forage plus a ration balancer is enough.

Common Mistakes Owners Make

Assuming “Senior Feed” Means Low Starch

Some senior feeds are low-starch. Some are not. Read the label.

Feeding Grain Because the Horse “Needs Something”

Many horses need vitamins, minerals, salt, and forage. They do not necessarily need a grain meal.

Removing Grain but Ignoring Pasture

Pasture can be a huge NSC source, especially in spring, autumn, stressed grass, sunny cool weather, and lush improved paddocks.

Using Rice Bran Without Checking Suitability

Rice bran can be useful for calories, but it is not automatically low-starch or suitable for every insulin-dysregulated horse. Merck specifically advises caution with rice bran in insulin-dysregulated horses. (Merck Veterinary Manual)

Over-Restricting an Overweight Horse Too Fast

Obese horses need calorie control, but sudden severe restriction can create other metabolic problems. UC Davis recommends weight-loss plans with veterinary guidance and gradual adjustment. (Center for Equine Health)

Treating Laminitis Risk Like a Feed Preference

A cresty-necked, footsore horse does not need a cute new feed scoop. It needs a proper metabolic and laminitis plan.

How To Prevent High-Starch Feeding Problems

Prevention starts with knowing which horse you are feeding.

Focus on:

• Body condition scoring every 2 to 4 weeks

• Neck crest monitoring

• Weight tape or scale tracking

• Hay and pasture analysis where needed

• Low-NSC forage for metabolic horses

• Measured feed, not scoop guessing

• Small concentrate meals if concentrates are needed

• Ration balancer instead of unnecessary grain

• Regular exercise if the horse is sound

• Grazing muzzle or dry lot use for high-risk horses

• Regular farrier care

• Blood testing for insulin dysregulation, EMS, or PPID when indicated

• Immediate veterinary care for laminitis signs

For metabolic horses, the target is not just “less grain.” It is controlled calories, controlled NSC, balanced minerals, safe exercise, and hoof protection.

Will My Horse Be Okay?

Most horses do well when the diet matches their body condition, age, workload, and metabolic status.

A lean, fit horse in proper work may tolerate starch as part of a balanced performance diet.

An overweight senior horse with a cresty neck, mild foot soreness, and a sweet feed habit is a completely different animal. That horse is waving several red flags while standing next to a feed bin.

The earlier you act, the better. Dietary changes before laminitis are far easier than trying to manage damaged feet after the fact.

FAQs

Are oats bad for horses?

Oats are not automatically bad. They are a grain and contain starch, so they need to be fed according to the horse’s workload, body condition, and metabolic risk. Oats may be inappropriate for overweight, insulin-dysregulated, or laminitis-prone horses.

What is considered a low-starch horse feed?

There is no single universal definition, but for metabolic horses the total NSC of the full diet matters most. UC Davis notes that forage for EMS horses should ideally be below 10% NSC on a dry matter basis. (Center for Equine Health)

Can high-starch feed cause colic?

High-starch feeding, especially large concentrate meals or sudden grain overload, can increase digestive upset and colic risk. Merck links high-starch and high-sugar concentrate-heavy rations with increased risk of colic, laminitis, and gastric ulcer syndrome. (Merck Veterinary Manual)

Should older horses avoid grain?

Not all older horses need to avoid grain, but senior horses should be fed more carefully. Older horses may have dental disease, PPID, insulin dysregulation, weight loss, or inflammatory changes that alter what is safest. Many do better on high-fibre, lower-starch diets with calories supplied through safer fibre and fat sources.

What should I feed an overweight horse instead of grain?

Start with controlled forage, a ration balancer, salt, and a veterinary weight-loss plan. For horses with EMS or laminitis risk, forage testing, pasture restriction, a grazing muzzle, and low-NSC feeding are often needed. Do not simply starve the horse.

Final Thoughts

High-starch feeds are not evil. But they are powerful, and powerful feeds need to be used with thought.

The research on IL-1β gives us a useful warning: older and overweight horses appear to respond more strongly to high-NSC meals from an inflammatory-marker standpoint. That does not mean every horse must be grain-free. It means the easy keeper, senior horse, cresty pony, PPID horse, EMS horse, and laminitis-prone horse deserve a much more careful feeding plan.

The safest diet is not always the trendiest one. It is the one matched to the horse’s age, body condition, workload, gut health, hoof risk, and metabolic status.

When in doubt, feed the horse in front of you. Not the bag. Not the label. Not the stable gossip committee, as passionate as they may be.

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If you are unsure whether your horse’s feed is too high in starch, or whether weight gain, a cresty neck, foot soreness, colic signs, or poor performance could be linked to the diet, ASK A VET™ can help you work through the risk and decide what needs to change.