Why Is My Horse Farting So Much?

Name: Why Is My Horse Farting So Much?
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Horses fart because their hindgut ferments fiber, and fermentation makes gas. Most of the time, a horse that passes gas often is simply a healthy horse with a working digestive tract. Why does my horse fart so much is a common question, and the honest answer is that some horses are just gassier than others. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Frequent farting in horses is usually normal. The large colon and cecum are fermentation vats, and gas is the natural byproduct.
Sudden increases often follow a feed change, rich pasture, alfalfa, or stress such as hauling or showing [1].
A gassy horse that is eating, drinking, pooping, and acting normal rarely needs urgent care.
Gas plus pawing, rolling, looking at the flank, or no manure for hours is a colic emergency. Call your veterinarian now.
Sand in the gut is a real concern in sandy regions. Even small amounts raise the odds of sand colic [2].

What Normal Horse Gas Looks Like

Flatulence in horses is audible and frequent. You may hear long, loud passages of gas, especially after a meal or during exercise. Some horses pass gas with every bowel movement. Others barely make a sound.

The key is the whole picture, not the gas alone. A normal gassy horse:

Eats and drinks as usual
Passes normal manure at a normal rate
Has normal temperature, pulse, and breathing
Shows no signs of pain
Behaves the same as always

Gas by itself is not a disease. It is a sign that microbes in the hindgut are breaking down fiber, which is exactly what they are supposed to do.

Why Horses Make So Much Gas

Horses are hindgut fermenters. The cecum and large colon hold trillions of bacteria, protozoa, and fungi that digest plant fiber. That process produces volatile fatty acids the horse uses for energy, plus methane and other gases. A horse on a high-fiber diet, such as good grass hay, will ferment a lot and may pass a lot of gas.

This is different from people. Your horse is not "gassy" in the same way a person with a sensitive stomach is. For a horse, gas is a normal output of a normal process.

Why Is My Horse Farting So Much? The Main Causes

Several things can push gas production up. Most are mild. A few are serious.

Diet and Feed Changes

The most common reason for a sudden increase in gas is a change in what the horse eats. Horses develop semiformed feces when first introduced to lush pastures, alfalfa hay, or a stressful situation such as a trailer ride, racing, showing, or a visit to a veterinary hospital [1]. That change in manure consistency often comes with more gas. It usually settles as the horse adapts to the new diet or the stress passes [1].

Rapid changes are the problem. The hindgut microbes need time to adjust to new feed. Switch hay, grain, or pasture gradually over one to two weeks when you can.

Rich Pasture and Spring Grass

Lush spring grass is high in sugar and starch that reaches the hindgut. The microbes ferment it fast, and gas production rises. Some horses also get loose manure during this transition [1]. If your horse is otherwise healthy, this is usually not medically important [1].

Stress

Hauling, showing, a new barn, or a new herdmate can change gut motility and manure consistency [1]. Stress alone can make a horse gassier for a day or two.

Sand Accumulation

Horses grazing on sandy ground can swallow sand, which settles in the colon. In a study of desert horses, the median sand depth was much greater in horses diagnosed with sand colic (112.16 mm) than in horses with non-sand colic (12.0 mm) or control horses (10.5 mm) [2]. For every millimeter of sand present, horses had a 2% increase in the odds of being diagnosed with sand colic [2]. Younger horses were more likely to be diagnosed with sand colic, but older horses were more likely to need surgery [2].

Gas can be an early hint of sand irritation. Watch for poor coat, weight loss, loose manure, or recurring mild colic in sandy areas.

Grain Overload and Other Serious Causes

Grain overload is a genuine emergency. Eating too much grain causes rapid fermentation, gas, and often severe diarrhea [1]. Other serious causes of diarrhea and gas include toxic plants and chemicals, antimicrobial treatment, and organ failure [1]. These are not "just gas" situations.

Cause Table

Cause	Typical clues	How urgent
Normal hindgut fermentation	Gassy but bright, eating, normal manure	Not urgent
Diet change or rich pasture	Recent feed switch, loose manure, gas for a few days [1]	Monitor closely
Stress (hauling, showing)	Gas and soft manure around travel or events [1]	Monitor closely
Sand accumulation	Sandy soil, poor coat, weight loss, mild colic [2]	Call your vet soon
Grain overload	Found in the feed, severe gas, diarrhea [1]	Emergency now
Toxic exposure or organ disease	Diarrhea, depression, other signs [1]	Emergency now

Red Flags That Mean Emergency

Gas is not the problem. Gas plus pain is. Call your veterinarian right away if you see:

Pawing, rolling, or repeatedly looking at the flank
No manure for several hours, or very little
A bloated, tight abdomen
Sweating, trembling, or a rapid pulse
Lying down more than usual and not wanting to get up
Diarrhea that is watery or lasts more than a day
Refusing to eat or drink
A horse that seems depressed or distant

Colic is a major cause of illness and death in horses, and it can move fast [3]. Do not wait to see if it passes on its own. If your horse is in pain, that is a same-day or emergency call.

If you are also managing other pets, some of the same "watch the whole picture" logic applies. A dog that pants heavily or a dog that coughs and gags needs the same kind of attention to red flags. You can read more about those signs in Why Is My Dog Panting So Much? and Why Does My Dog Cough And Gag So Much.

What You Can Safely Do at Home

If your horse is gassy but acting normal, you can take a few sensible steps while you watch for changes.

Keep the Routine Steady

Feed the same hay at the same times. Sudden changes in amount or type are the most common trigger for extra gas [1]. If you must switch feed, do it slowly over one to two weeks.

Limit Rich Pasture

If spring grass is the likely cause, use a grazing muzzle or limit turnout hours. Introduce lush pasture gradually. The manure and gas usually settle once the horse adapts [1].

Offer Fresh Water

Water keeps ingesta moving through the gut. A horse that drinks well is less likely to have a gut slowdown.

Provide Movement

Turnout and light exercise help gut motility. A stalled horse with no movement can get gassier and more uncomfortable.

Do Not Give Human Gas Medication

Do not reach for simethicone or any human product. There is no dose for horses that applies to every pet, and the wrong product can do harm. Your veterinarian calculates any medication dose from your horse's weight and health.

Watch Manure and Behavior

Count bowel movements. Note the consistency. Check for sand in the manure by putting a few fresh balls in a bucket of water and looking for grit at the bottom. This is a simple screening trick, not a diagnosis.

Check the Environment

Look for toxic plants, spilled grain, or new supplements. Grain overload and toxic exposures cause diarrhea and gas and need immediate care [1]. If you suspect a poison, call your veterinarian and a poison control hotline right away.

What Your Veterinarian Will Check

When you call about excessive gas, your veterinarian will start with a full physical exam. That includes temperature, pulse, respiration, gut sounds, and a pain assessment.

History Questions

Expect questions about diet, recent changes, pasture, turnout, travel, deworming, and how long the gas has been going on. Bring notes if you can.

Hands-On Exam

Your vet will palpate the abdomen and listen for gut sounds. They may check for sand sounds in the ventral abdomen.

Rectal Examination

A rectal exam is common in horses with colic. It helps locate gas, impactions, or displacement. One study found that rectal exam findings matched surgical findings in 57.2% of cases when only the primary diagnosis was considered, rising to 71.6% when primary and additional findings were combined [4]. That means the rectal exam is useful but not perfect, and it is one piece of the puzzle.

Blood Work and Imaging

Blood tests can check hydration, electrolytes, and organ function. In horses with colic, blood and peritoneal markers of oxidative stress and antioxidant defense differ from healthy horses, and these patterns relate to the type of colic and the outcome [3]. Your vet may also measure peritoneal fluid lipase, which has been associated with strangulating lesions, pancreatic fibrosis, and negative outcomes in horses with colic [5]. Abdominal radiographs or ultrasound can show sand depth, which matters because deeper sand raises the odds of sand colic [2].

Treatment

Treatment depends on the cause. Mild diet-related gas may need only a gradual feed transition [1]. Sand may need a specific plan your vet designs. Colic may need pain relief, fluids, or surgery. Foals on certain liquid diets have shown flatulence, mild bloat, and very mild abdominal pain, with complete recovery without therapy within 6 hours [6]. That is a reminder that even young horses can show gas as a sign of diet intolerance.

Prevention and Monitoring

You cannot stop a horse from fermenting fiber, and you should not try. You can keep the hindgut stable.

Make feed changes slowly over one to two weeks.
Introduce lush pasture gradually, and use a muzzle if needed.
Feed good-quality fiber and keep meal sizes reasonable.
Provide constant access to clean water.
Maximize turnout and movement.
Manage sand exposure. Do not feed on sandy ground, and use mats or feeders.
Watch manure daily for consistency and sand.
Keep a simple log of gas, manure, and behavior so you notice trends.

If your horse is gassy but healthy, that is often just normal horse digestion doing its job. If the gas comes with pain, diarrhea, or a change in attitude, treat it as a medical concern.

Limitations and When to Contact a Veterinarian

This article cannot tell you what is happening inside your specific horse. Only a veterinarian who examines your horse can do that. Individual cases need a veterinarian, and timing matters.

Call now, as an emergency, if your horse is rolling, sweating, pawing, bloated, or in obvious pain. Call the same day if your horse has watery diarrhea, has not passed manure in several hours, is off feed, or seems depressed. Call for a routine visit if the gas is new, has lasted more than a few days, or comes with weight loss, poor coat, or loose manure.

Do not wait for a "maybe." Colic can worsen quickly, and early treatment is better than late treatment [3]. If you are unsure, call and describe what you see. Your veterinarian would rather answer a question than treat a crisis.

Frequently Asked Questions

Is it normal for a horse to fart a lot?

Yes, frequent farting is normal for many horses. The hindgut ferments fiber, and gas is the natural result. A gassy horse that eats, drinks, and acts normal is usually fine.

Can diet cause excessive gas in horses?

Yes, diet is the most common trigger. New hay, grain, lush pasture, or alfalfa can increase gas and soften manure while the gut adapts [1]. Slow feed changes prevent most of this.

Does sand in the gut cause gas?

Sand can irritate the colon and lead to gas, loose manure, and colic. Deeper sand accumulation is linked to higher odds of sand colic [2]. If you live on sandy ground, ask your vet about screening.

When should I worry about horse flatulence?

Worry when gas comes with pain, bloating, no manure, diarrhea, or a dull attitude. Those signs point to colic or another serious problem and need a veterinarian right away [3].

Can I give my horse gas medicine?

No, do not give human gas medicine or any over-the-counter product without veterinary guidance. There is no safe horse dose that applies to every pet, and your veterinarian will calculate any treatment based on your horse's weight and health.

If you notice other pets with changes in appetite, thirst, or breathing, those signs deserve the same attention. You can read about increased drinking and urination in Why Is My Dog Peeing So Much? and about itchy skin in Why Is My Dog So Itchy?.

References

Miscellaneous Causes of Diarrhea in Horses - Digestive System. Merck Veterinary Manual.
Depth and distribution of colonic sand accumulation in a desert population of horses and its association with diagnosis of sand colic. Journal of the American Veterinary Medical Association, 2026.
Evaluation of oxidative stress and antioxidant defense biomarkers in healthy and colic horses: correlation with type of colic and outcome. Journal of veterinary internal medicine, 2026.
Comparison of Rectal and Intraoperative Findings in Horses with Colic. Animals : an open access journal from MDPI, 2026.
Activity of 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester lipase in peritoneal fluid may be associated with strangulating lesions, pancreatic fibrosis, and negative outcome in horses with colic. Journal of the American Veterinary Medical Association, 2026.
A preliminary study of the tolerance of healthy foals to a low residue enteral feeding solution. Equine veterinary journal, 1991.