Digestion

Gas & Bloating in Horses: Causes & What to Check

Horses naturally produce gas as microbes ferment feed in the hindgut, but owners often notice periods when a horse seems unusually gassy, looks bloated or becomes uncomfortable. Diet and pasture can influence fermentation, while sudden painful distention can indicate something more serious. Here is how to tell the difference and what to check first.

Written by Ben Nedas Reviewed by Dr Rosemary Waring

Quick answer

What horse owners need to know

Some intestinal gas is completely normal in horses because hindgut microbes produce gas while fermenting the diet.

A horse may become noticeably gassier when pasture, forage or concentrate intake changes, particularly when more rapidly fermentable carbohydrate reaches the hindgut.

However, visible abdominal distention can also occur when gas is not moving normally through the digestive tract and may be associated with colic or obstruction.

Start by checking recent diet and pasture changes, concentrate meal size, forage intake, manure output and whether the horse is otherwise comfortable.

If bloating is sudden or accompanied by pain, reduced appetite, reduced manure production, rolling, sweating or other colic signs, contact your veterinarian promptly.

Start with the horse

Understanding what you're seeing

What you may notice

Some horses are naturally more obviously gassy than others, but a change from your horse's normal pattern is worth noticing.

You may observe:

• More frequent passing of gas
• Louder intestinal sounds
• A visibly fuller or more distended abdomen
• Increased gas around manure passage
• Changes in manure consistency
• Loose manure or excess fecal water
• Restlessness after feeding
• Looking at the flank
• Stretching
• Reduced appetite
• Mild recurrent abdominal discomfort
• A pattern linked to pasture, feed or management changes

Passing gas by itself is not necessarily a problem.

The important questions are whether it represents a new change, whether the horse appears comfortable, and whether other digestive signs are occurring at the same time.

Sudden distention, pain or significant behavioral change should be treated differently from an otherwise comfortable horse that simply passes gas frequently.

Common causes

Gas is produced naturally during hindgut fermentation, so an increase in gassiness does not always indicate disease.

Factors that may contribute to increased fermentation or gas include:

• Sudden changes in pasture
• Lush or highly fermentable grass
• Large grain or concentrate meals
• Excess starch reaching the hindgut
• Abrupt changes in hay or forage
• Rapid dietary change
• Changes in microbial fermentation
• Reduced forage intake
• Stress and changes in routine
• Individual responses to particular feeds or forage

Gas can also accumulate when it is not moved normally through the gastrointestinal tract.

Inflammation, altered intestinal motility, obstruction or displacement can therefore cause intestinal distention even when excessive fermentation was not the original problem.

This is why sudden bloating accompanied by abdominal pain should not be approached as a simple feed intolerance.

What should you check first?

Start by distinguishing normal fermentation from a genuine change.

1. Is the horse actually bloated?

A naturally rounded abdomen is different from sudden or obvious abdominal distention. Compare the horse with its normal appearance.

2. Is there any pain?

Pawing, flank-watching, stretching, repeatedly lying down or rolling changes the situation from a feeding observation to a potential colic concern.

3. Has the pasture changed?

Recent turnout onto lush grass, rapidly growing pasture or a significant increase in grazing time can alter hindgut fermentation.

4. Has the feed changed?

Look for a new concentrate, new forage source, larger meal size or increased grain intake.

5. How much starch is being fed at one time?

Large starch loads increase the chance that some starch will escape digestion before reaching the hindgut.

6. Has forage intake changed?

Reduced forage, long periods without hay or a sudden change in forage type can alter the normal fermentation pattern.

7. What does the manure look like?

Loose manure, excess fecal water or marked changes in fecal consistency may provide additional evidence that digestion has changed.

8. Is the horse passing manure normally?

Reduced fecal output alongside abdominal discomfort requires veterinary attention.

9. Is there a recurring pattern?

Record pasture conditions, feed, travel, competition, turnout and other management factors when episodes occur.

Patterns are often more informative than a single isolated observation.

Feeding & management steps

Management should focus on promoting consistent digestion rather than trying to eliminate normal gas production.

Useful principles include:

• Make forage the foundation of the ration
• Avoid abrupt changes in hay, pasture or concentrate feed
• Introduce new pasture gradually where possible
• Avoid unnecessarily large grain or concentrate meals
• Split required concentrate intake across smaller meals
• Review the starch content of the total ration
• Match concentrate feeding to the horse's actual workload
• Avoid long periods without forage where possible
• Maintain regular access to clean, fresh water
• Review pasture management during periods of rapid grass growth
• Keep dental care up to date
• Maintain an appropriate parasite-control program with veterinary guidance
• Encourage normal movement and turnout where appropriate
• Keep a record of feed, pasture and management changes when recurrent gassiness occurs

If a horse repeatedly becomes gassy following a particular feed, forage source or management change, that pattern can be useful when reviewing the ration.

Make changes gradually and one at a time where practical. Changing several feeds and supplements simultaneously makes it difficult to identify what was actually responsible.

When to contact your veterinarian

Sudden abdominal distention or apparent gas accompanied by pain should be treated seriously.

Contact your veterinarian promptly if your horse is pawing, repeatedly looking at the flank, lying down, rolling, sweating, stretching, refusing food, becoming depressed, passing less manure than normal or showing persistent or increasing abdominal discomfort.

Visible abdominal enlargement that develops suddenly also warrants veterinary advice, particularly when accompanied by behavioral changes or pain.

Gas can cause intestinal distention and colic, but similar signs can also occur with obstruction, displacement and other gastrointestinal conditions.

Do not assume that recurrent abdominal pain is harmless simply because previous episodes have been described as “gas colic.”

A veterinarian can determine whether the horse requires examination and treatment.

The digestive connection

Where digestion fits

Gas production is a normal part of the horse's digestive system.

The cecum and large colon act as enormous fermentation chambers. Microorganisms living there break down material that the horse cannot digest enzymatically earlier in the gastrointestinal tract, particularly fiber.

This microbial fermentation provides an important source of energy for the horse, but it also naturally produces gas.

What reaches the hindgut influences how fermentation proceeds.

Fiber is the substrate the equine hindgut is designed to ferment. When larger quantities of rapidly fermentable carbohydrate such as undigested starch or pasture fructans arrive, the rate and pattern of fermentation can change.

This can alter microbial populations, acid production and gas production.

Excessive intestinal gas can also result from difficulty moving gas normally through the gastrointestinal tract, meaning that not every gas problem is simply a consequence of excessive fermentation.

That distinction matters: dietary management can support a stable fermentation environment, but painful gas accumulation or intestinal distention requires veterinary assessment.

EquiNectar research

What the research tells us about diet and the hindgut environment

EquiNectar research has shown that both pasture and digestive supplementation can produce measurable changes in the equine hindgut environment.

In a controlled study involving 45 horses, researchers examined what happened to fecal metabolites during a six-week transition onto spring pasture.

The pasture transition altered metabolite profiles, demonstrating that a change in grass intake can measurably affect the digestive microbial environment.

Horses receiving EquiNectar showed a different metabolite response from the control group, with their profiles remaining more consistent with baseline during the pasture transition.

A separate study of Thoroughbred racehorses also measured a change in fecal pH during EquiNectar supplementation, providing further evidence that digestive supplementation can influence measurable conditions downstream in the gastrointestinal tract.

These studies are relevant to gas because microbial fermentation is responsible for gas production in the hindgut and is strongly influenced by the dietary material available to the microbial population.

However, neither study measured gas production or abdominal bloating as a primary outcome, so the results should not be interpreted as evidence that EquiNectar treats excessive gas.

45 horses Horses in a controlled study of spring pasture and digestive supplementation

6 weeks Duration of the controlled spring-pasture study

72 horses Horses included in a separate racehorse fecal-pH analysis

What this research does — and doesn't — tell us

EquiNectar studies have demonstrated measurable changes in the equine digestive environment, including fecal microbial communities, metabolite profiles and fecal pH.

However, the existing studies were not designed specifically to investigate excessive gas, abdominal bloating or gas colic.

Changes in fecal metabolites, microbiota or pH should therefore not be interpreted as proof that EquiNectar reduces intestinal gas or prevents gas colic.

Gas production is influenced by diet, microbial fermentation and gastrointestinal motility, while abdominal distention can have causes that require veterinary investigation.

The available research supports EquiNectar's role as a digestive supplement. It does not establish EquiNectar as a treatment for abdominal pain, intestinal distention or any underlying disease.

Where EquiNectar fits

Supporting digestion as part of good management

EquiNectar is designed to support digestion and the gastrointestinal environment rather than treat gas, bloating or colic.

Its Enzyme Rich Malt Extract provides naturally occurring digestive enzyme activities including amylase, fructanase, cellulase, xylanase, beta-glucanase, protease, lipase and phytase.

These enzymes act on different components of feed and forage during digestion.

This is relevant because the amount and type of dietary material arriving in the hindgut influence microbial fermentation. Supporting digestion earlier in the digestive tract can therefore alter the substrate available to hindgut microorganisms.

EquiNectar should sit alongside good feeding practice: consistent forage, sensible concentrate meal sizes, gradual dietary change, appropriate pasture management, clean water, dental care and veterinary investigation when signs warrant it.

A horse with sudden abdominal distention or signs of pain needs veterinary assessment rather than supplementation alone.

Explore EquiNectar

Common questions

Frequently asked questions

Is it normal for horses to produce gas?

Yes. Gas is a normal by-product of microbial fermentation in the horse's hindgut. The cecum and colon contain a large population of microorganisms that ferment fiber and other dietary material. This process produces useful nutrients for the horse as well as gases. The concern is not the existence of gas itself, but an unusual increase in gas production, visible abdominal distention, recurrent discomfort or an inability to move gas normally through the digestive tract.

Why is my horse suddenly very gassy?

A sudden increase in gas can occur when hindgut fermentation changes. Possible triggers include lush pasture, a change in hay or concentrate feed, large grain meals, increased rapidly fermentable carbohydrate intake or an abrupt change in diet. Gas accumulation can also occur when normal intestinal movement is disrupted, so a horse that is painful, visibly distended or otherwise unwell should not simply be assumed to have a harmless feeding-related problem.

Can grass make a horse gassy or bloated?

Yes. Changes in pasture can alter what reaches the hindgut and therefore change microbial fermentation. Lush grass can supply substantial amounts of rapidly fermentable carbohydrate. Sudden increases in pasture intake may therefore change fermentation, manure consistency and gas production in some horses. Gradual pasture introduction and consistent management are particularly useful when grass conditions are changing quickly.

Can too much grain cause gas in horses?

It can contribute. Starch is primarily intended to be digested before it reaches the hindgut. If a large amount escapes digestion in the small intestine, hindgut bacteria can ferment it rapidly. That can increase acid production, alter the microbial environment and change fermentation patterns. Managing meal size and overall starch intake is therefore an important part of supporting hindgut stability.

Is a bloated belly in a horse always caused by gas?

No. A rounded abdomen can reflect body shape, forage intake, pregnancy, reduced abdominal muscle tone or other factors and is not necessarily evidence of excessive intestinal gas. Sudden abdominal enlargement or obvious distention is different, particularly if it is accompanied by pain, reduced appetite, sweating, pawing, looking at the flank, lying down or rolling. Those signs require prompt veterinary advice.

When is gas in a horse a sign of colic?

Gas can distend sections of the digestive tract and cause abdominal pain. Contact your veterinarian promptly if increased gas or abdominal distention is accompanied by signs such as pawing, repeatedly looking at the flank, lying down, rolling, sweating, reduced appetite, reduced manure production, depression or persistent discomfort. It is not possible to determine the seriousness of abdominal pain simply by assuming it is “only gas.”

Can EquiNectar help support a horse that is often gassy?

EquiNectar is designed to support digestion rather than treat gas colic or abdominal distention. Its Enzyme Rich Malt Extract supplies naturally occurring digestive enzyme activities that help break down components of feed and forage. The rationale is to support digestion before dietary material reaches the hindgut, helping influence the substrate available for microbial fermentation. EquiNectar studies have demonstrated measurable changes in fecal metabolites, microbial communities and fecal pH, but gas or bloating has not been tested as a primary outcome. It should therefore not be presented as a treatment for excessive gas.

What horse owners need to know

Understanding what you're seeing

Where digestion fits

What the research tells us about diet and the hindgut environment

Supporting digestion as part of good management

Frequently asked questions

Related horse health guides

Loose Manure & Excess Fecal Water in Horses: Causes & What to Check

Hindgut Acidosis in Horses: Signs, Causes & Management