Are High-Starch Feeds Bad for Horses?

By Dr Duncan Houston

Grain and high-starch feeds have helped fuel performance horses for generations, but they are not the right answer for every horse.

For some horses, especially older horses, overweight horses, easy keepers, horses with equine metabolic syndrome, PPID, insulin dysregulation, previous laminitis, ulcers, or recurrent colic, a high-starch diet can create more risk than benefit.

The concern is not that starch is “toxic” in every situation. The concern is matching the feed to the horse. A fit racehorse in hard work and an overweight, cresty-necked pony in light work do not need the same nutrition plan. Feed them the same way and the pony usually pays the price.

Quick Answer

High-starch feeds are not automatically bad, but they can increase digestive, metabolic, and inflammatory risk in the wrong horse. Research in horses has shown that high non-structural carbohydrate meals can raise interleukin-1β, a pro-inflammatory marker, especially quickly in older and overweight horses. For horses at risk of laminitis, EMS, ulcers, or colic, the safer approach is usually forage-first feeding, controlled calories, low-NSC forage, and carefully chosen low-starch calorie sources. (MDPI)

What Counts as a High-Starch Feed?

Starch is a type of non-structural carbohydrate, often grouped with sugars and fructans under the term NSC.

Common high-starch or high-NSC feeds include:

• Oats

• Corn

• Barley

• Sweet feed

• Cereal grain mixes

• Some high-energy concentrates

• Some pelleted feeds, depending on formulation

• Molasses-heavy feeds

• Large meals of grain-based concentrate

Not every bagged feed is high-starch, and not every low-starch feed is automatically low-calorie. The label matters. So does the amount fed.

MSD Veterinary Manual notes that most healthy horses should have free access to forage, salt, and fresh water, and many horses on good-quality forage need little or no concentrate supplementation. It also warns that feeding more than 50 percent of the ration dry matter as high-starch or high-sugar concentrate increases the risk of laminitis, colic, and equine gastric ulcer syndrome. (MSD Veterinary Manual)

What Is IL-1β and Why Does It Matter?

Interleukin-1β, or IL-1β, is a 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 about to develop laminitis, arthritis, colic, ulcers, or cognitive decline. That would be overstating the research.

What it does mean is that the body is showing an inflammatory response. In nutrition, that matters because repeated inflammatory signals can be part of a bigger risk picture, especially in older, overweight, metabolically vulnerable, or insulin-dysregulated horses.

A 2021 study from Sam Houston State University investigated how age and body condition affected IL-1β responses after high-NSC meals. The researchers found that younger, leaner horses needed repeated exposure to high-starch meals before showing a post-meal IL-1β rise, while older and heavier-conditioned horses showed elevated post-meal IL-1β from the first day of feeding and afterward. (MDPI)

What Did the High-Starch Study Actually Show?

The study used steam-rolled barley to provide 1.2 g of non-structural carbohydrate per kilogram of body weight.

In the body condition trial, middle-aged horses were grouped as lean or overweight. The overweight horses showed a post-meal IL-1β increase earlier, while lean horses showed increased mean IL-1β after 14 days of daily high-NSC feeding. In the age trial, older horses had an enhanced IL-1β plasma response compared with middle-aged horses after the high-NSC feeding period. (MDPI)

The practical takeaway is not “never feed grain.”

The practical takeaway is:

Older and overweight horses appear less tolerant of repeated high-starch meals from an inflammatory standpoint, so their diets should be managed more cautiously.

Why High-Starch Meals Can Be a Problem

Horses evolved to eat forage over many hours. Their digestive system is built around trickle feeding, fibre fermentation, and steady movement of feed through the gut.

Large starch meals can create problems in several ways.

First, if too much starch reaches the hindgut, it can alter fermentation patterns and disrupt the microbial environment. Second, high-concentrate diets can increase digestive risk. Third, for insulin-dysregulated horses, high sugar and starch intake can worsen insulin responses and raise laminitis risk. MSD specifically recommends limiting grain-based concentrate meal size and splitting larger concentrate amounts into multiple smaller meals. (MSD Veterinary Manual)

High-starch feeding can also matter for gastric ulcers. MSD describes high-concentrate grain diets, low roughage intake, intermittent feeding, stress, travel, and performance work as risk factors for equine gastric ulcer syndrome. (MSD Veterinary Manual)

In practice, the real problem is usually not one small feed of oats. It is the repeated mismatch between horse, workload, body condition, medical risk, and ration design.

Which Horses Are Most at Risk?

High-starch feeds deserve extra caution in:

• Overweight horses

• Easy keepers

• Ponies

• Donkeys

• Miniatures

• Horses with a cresty neck

• Horses with equine metabolic syndrome

• Horses with insulin dysregulation

• Horses with PPID

• Horses with previous laminitis

• Horses with recurrent foot soreness after grass or grain

• Senior horses, especially those over 20

• Horses with recurrent colic

• Horses with gastric ulcers

• Horses on stall rest or light work

• Horses with poor gut tolerance to grain

UC Davis describes EMS treatment as involving NSC restriction, calorie control, reduced or eliminated pasture access when needed, and exercise when the horse is sound enough. It also notes that hay analysis is important, with NSC ideally below 10 percent of dry matter for many horses with EMS. (Center for Equine Health)

The horse I worry about most is the one described as “a good doer” but still given a traditional grain feed because that is what every horse in the barn gets. That horse often does not need more energy. They need fewer calories, lower NSC, better minerals, and more movement.

Are High-Starch Feeds Ever Appropriate?

Yes.

Some horses genuinely need more energy than forage alone provides. High-performance horses, lactating mares, growing horses, and hard keepers may need concentrates as part of a balanced ration.

The issue is not whether starch can ever be fed. The issue is how much, how often, to which horse, and why.

A sensible high-starch feed plan is more likely to be appropriate when:

• The horse is lean or in ideal condition

• The workload is high enough to justify the calories

• The horse has no history of laminitis

• There is no known insulin dysregulation

• Concentrate meals are small and split

• The diet is still forage-based

• The horse has normal manure, appetite, feet, and behaviour

• The ration is balanced for vitamins and minerals

University of Minnesota Extension notes that forages can often meet a horse’s energy needs, that cereal grain meals should not exceed 0.5 percent of body weight at one time, and that fat can be used to increase energy density while avoiding overfeeding cereal grains. (University of Minnesota Extension)

Severity Guide: How Risky Is Your Horse’s Current Feed?

The most important distinction is this: a controlled concentrate ration is one thing; a high-risk horse on unnecessary starch is another.

When Is This an Emergency?

High-starch feeding becomes urgent when it is linked to grain overload, colic, laminitis, choke, or sudden illness.

Call your vet immediately if your horse has:

• Broken into the feed room

• Eaten an unknown amount of grain or sweet feed

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

• Little or no manure

• Reduced appetite after a grain meal

• Tacky gums or abnormal gum colour

• Severe diarrhea

• Reluctance to walk

• Heat in the feet

• Strong digital pulses

• A pottery or “walking on eggshells” gait

• A rocked-back stance

• Collapse, weakness, or marked depression

AAEP lists acute laminitis signs including lameness, heat in the feet, increased digital pulse, toe pain, a hesitant gait, and a sawhorse stance, and advises horse owners to seek veterinary help immediately when laminitis is suspected. It also specifically warns that if a horse breaks into the feed room and overeats grain, owners should call a veterinarian immediately rather than waiting for symptoms to develop. (AAEP)

Colic signs such as flank watching, rolling, reduced manure, dry or mucus-covered manure, poor appetite, abnormal drinking, tacky gums, and elevated heart rate also need prompt veterinary attention. (University of Minnesota Extension)

What Else Can Look Like a “Reaction to Grain”?

Owners sometimes blame high-starch feed for every behaviour or health change after feeding. Sometimes they are right. Sometimes something else is going on.

Important rule-outs include:

Equine gastric ulcer syndrome
A horse with poor appetite, girthiness, poor performance, mild colic, attitude changes, or weight loss may have ulcers. High-concentrate diets and low roughage intake can contribute, but diagnosis and treatment need veterinary guidance. (MSD Veterinary Manual)

EMS or insulin dysregulation
Weight gain, a cresty neck, fat pads, laminitis history, or foot soreness after grass or grain should trigger metabolic testing.

PPID
Older horses with coat changes, muscle loss, recurrent infections, laminitis, or abnormal fat distribution may need PPID testing.

Dental disease
A senior horse losing weight may not need more grain. They may need dental care and a forage replacement strategy.

Pain or poor workload fit
Irritability, poor performance, or reluctance to work can come from pain, saddle fit, lameness, ulcers, or behaviour issues, not just feed.

Too many calories overall
Some horses are not reacting to starch specifically. They are simply overfed for their workload.

Poor forage quality
A horse on poor hay may be given more grain to compensate, when the better answer is often better forage.

What Should You Do Right Now?

1. Read the feed label

Look for starch, sugar, NSC, feeding rate, fat, fibre, and calories.

Do not rely on the marketing name. “Senior,” “performance,” “cool,” “complete,” or “safe” does not automatically mean low-starch or suitable for a metabolic horse.

2. Weigh the feed

Scoops lie. Scales tell the truth.

Weigh:

• Hay

• Chaff

• Pellets

• Sweet feed

• Balancer

• Beet pulp

• Rice bran

• Oil or fat supplement

Many horses are overfed because nobody knows what the scoop actually weighs.

3. Make forage the foundation

Most horses should be managed around good-quality forage first, with concentrates added only when the horse genuinely needs them. MSD notes that many horses on good-quality forage require little to no concentrate supplementation. (MSD Veterinary Manual)

A good base plan usually includes:

• Appropriate hay or pasture

• Clean water

• Salt

• A ration balancer or vitamin and mineral support when needed

• Concentrates only to fill a real calorie or performance gap

4. Test hay for high-risk horses

For EMS, laminitis-prone, insulin-dysregulated, or obese horses, hay testing is not fancy. It is practical.

UC Davis recommends feed analysis to determine forage NSC content and notes that hays vary widely. University of Minnesota Extension also notes that forages high in carbohydrates can be problematic for horses prone to laminitis and metabolic disease, with 10 to 12 percent or less carbohydrate often used as a target for sensitive horses. (Center for Equine Health)

5. Reduce starch gradually

Do not suddenly overhaul the entire diet unless your vet is managing an emergency.

For stable horses, change gradually over 7 to 14 days, longer if the horse has a sensitive gut.

A safer transition may include:

• Reducing grain meal size

• Splitting meals

• Increasing appropriate forage

• Replacing calories with beet pulp, fat, or low-starch feeds where suitable

• Using a ration balancer instead of a calorie-heavy concentrate

• Removing molasses-heavy feeds when not needed

6. Use safer calorie sources when needed

For horses that need calories but should avoid high starch, options may include:

• Beet pulp

• Soy hulls

• Vegetable oil

• Flaxseed

• Low-starch, high-fat commercial feeds

• Low-NSC senior or complete feeds where appropriate

• Carefully selected forage replacements

Rice bran can be useful for some horses, but it is not automatically low-starch or low-sugar. MSD cautions that rice bran should be avoided or used with extreme caution in insulin-dysregulated horses unless guided by a qualified equine nutritionist. (MSD Veterinary Manual)

7. Monitor the feet, not just the feed tub

For at-risk horses, track:

• Digital pulses

• Hoof heat

• Turning comfort

• Stride length

• Willingness to move

• Body condition score

• Cresty neck changes

• Manure quality

• Appetite and behaviour

Early laminitis can be subtle. Waiting until the horse is obviously crippled is too late.

Common Mistakes Owners Make

Assuming every horse needs grain

Many horses do not. Light-work horses and easy keepers often need forage, minerals, salt, and controlled calories, not cereal grain.

Feeding senior horses more starch by default

Some older horses need calories. Others need dental care, PPID testing, protein, or a forage replacement. Age alone does not mean “add grain.”

Using high-starch feeds for weight gain without diagnosis

A thin horse may have dental disease, ulcers, parasites, chronic pain, PPID, inflammatory bowel disease, or poor forage access. More grain can hide the real problem.

Treating rice bran as automatically metabolic-safe

Rice bran adds fat and calories, but it is not automatically low-NSC. Use caution in insulin-dysregulated horses.

Making sudden diet changes

Rapid changes can disrupt the gut and make it hard to know what helped or harmed.

Ignoring hay NSC

For many laminitis-prone horses, the hay or pasture matters more than the tiny “token feed” in the bucket.

How To Feed With Inflammation and Metabolic Risk in Mind

A practical low-starch strategy looks like this:

• Start with forage analysis when possible

• Choose low-NSC forage for sensitive horses

• Avoid unrestricted lush pasture in high-risk horses

• Use a grazing muzzle or dry lot when needed

• Keep body condition controlled

• Add calories from fibre and fat before cereal starch

• Use a ration balancer for minerals and protein when calories are not needed

• Split concentrate meals

• Avoid large grain meals before transport, hard exercise, or stress

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

• Monitor feet closely after any diet or pasture change

The best nutrition plan is not the one with the trendiest bag. It is the one that matches the horse in front of you.

Will My Horse Be Okay?

Most horses do well when the diet is corrected before problems become advanced.

If your horse is lean, active, metabolically healthy, and fed modest concentrate meals, starch may be a useful energy source.

If your horse is older, overweight, insulin-dysregulated, ulcer-prone, laminitis-prone, or a classic easy keeper, reducing starch and building a forage-first plan can significantly lower risk. The aim is not to starve the horse. The aim is to feed energy safely, control insulin triggers, support gut stability, and prevent the feet from becoming the warning system.

FAQs

Are oats bad for horses?

Oats are not automatically bad. They can be appropriate for some hard-working horses when fed in controlled amounts. They are a problem when fed unnecessarily, in large meals, or to horses with EMS, insulin dysregulation, obesity, laminitis risk, or poor grain tolerance.

Can high-starch feeds cause laminitis?

High-starch and high-sugar feeding can increase laminitis risk, especially when large concentrate meals are fed or when the horse is already insulin-dysregulated or metabolically vulnerable. Active laminitis signs should be treated as an emergency.

What is the safest feed for an EMS horse?

Most EMS horses need controlled calories, low-NSC forage, salt, minerals, and restricted pasture access. Some may need a ration balancer or carefully selected low-starch feed. The exact plan should be based on body condition, insulin testing, forage analysis, and veterinary guidance.

Should I remove all grain from my horse’s diet?

Not always. Some performance horses or hard keepers need concentrates. The goal is not zero grain for every horse. The goal is the right amount for the horse’s workload, body condition, and medical risk.

What can I feed instead of high-starch grain?

Depending on the horse, safer options may include tested forage, beet pulp, soy hulls, vegetable oil, flaxseed, low-starch complete feeds, and ration balancers. For laminitis-prone or insulin-dysregulated horses, choose feeds only after checking NSC and calorie content.

Final Thoughts

High-starch feeds are not evil. They are simply powerful tools that are often used on the wrong horse.

The research on IL-1β adds another layer to what vets and nutritionists already worry about: older and overweight horses appear more sensitive to high-NSC meals, and repeated exposure may create inflammatory responses even in leaner horses over time. That does not mean panic. It means feed with more precision.

Forage first. Weigh the feed. Know the horse’s body condition. Test hay when risk is high. Keep grain meals small. Use fat and fibre when safer calories are needed. Most importantly, do not wait for laminitis, colic, or ulcers to prove that the ration was wrong.

Good feeding is not about tradition. It is about matching the diet to the horse’s biology.

If you are unsure whether your horse’s feed is too high in starch, whether they need EMS testing, or how to build a safer low-NSC diet, ASK A VET™ can help you work through the signs and decide what to do next.