Flatulence in dogs: causes, diet and investigations

Overview

Not all intestinal gas needs eliminating: gas production and passage are normal parts of digestion. Occasional burping and stomach rumbling can also be normal. Gas quantities vary considerably between dogs. However, excessive or clearly changed signs can relate to a feeding problem or gastrointestinal disease.

Gas has 3 main sources: swallowed air, production in the intestine and movement from blood into the intestine. Most gas passed through the anus is odourless. Sulphur-containing gases, such as hydrogen sulphide, are particularly responsible for unpleasant smells. Smell and total gas quantity are therefore different issues.

Causes

Swallowed air and bacterial fermentation produce gas

Eating quickly can increase air swallowing. Swallowed air can pass as a fart within just 2 hours. Colonic bacteria produce gas when fermenting carbohydrates and fibre. Poorly digested food leaves more material available for bacterial fermentation in the colon.

Fibre's effect depends on its type, rather than quantity alone. Rapidly fermentable fibre can increase gas and short-chain fatty acid production. More slowly fermentable fibres can increase stool bulk by holding water. Pea- and soya-based ingredients may increase flatulence in some dogs, depending on their quantity.

Normally, digestion breaks proteins, carbohydrates and fats into smaller components that can be absorbed through the intestinal wall. The pancreas secretes a large proportion of digestive enzymes. Dogs are also adapted to use carbohydrate-containing food.

Intestinal microbes also help produce vitamins and other nutrients. They support intestinal epithelial function. The microbiota also helps defend against intestinal pathogens. A change in bacterial composition is called dysbiosis. This can disrupt the balance of intestinal metabolism and immune defence.

Persistent signs may relate to digestive disease

Food hypersensitivity or chronic intestinal inflammation can cause digestive signs and increased gas. Intestinal parasites and eating unsuitable material are also common causes of digestive upset. A lack of pancreatic digestive enzymes can impair food breakdown and nutrient absorption.

Peristalsis means muscular movements that carry intestinal contents forwards. Other contractions mix food within the intestine. Reduced intestinal movement can allow gas and fluid to accumulate. Similar swelling can occur with a foreign body or intussusception. Abdominal size alone therefore cannot establish whether this is ordinary flatulence.

Risk factors

Gulping food and competition at mealtimes can maintain air swallowing. A diet rich in readily fermentable ingredients can increase gas. Beans and cabbages, for example, contain readily fermentable carbohydrates. Fruit pectin can also increase bacterial gas production.

A prebiotic supplement can increase flatulence as intestinal bacterial activity changes. Some dogs receiving probiotics also initially produce more gas. Underlying malabsorption becomes a particular consideration if your dog loses weight despite a good or increased appetite.

Intestinal lining damage can also cause secondary intolerance of lactose, or milk sugar. Dairy products may therefore worsen digestive signs in an animal with diarrhoea.

Typical symptoms

With ordinary flatulence, your dog may otherwise behave, eat and pass stools normally. Loud intestinal noises are called borborygmi.

• Your dog farts more often or smells worse.
• Burping increases.
• There are obvious rumbling or gurgling abdominal noises.
• The abdomen looks swollen or your dog seems uncomfortable around it.
• Stools become loose or your dog develops diarrhoea.
• Weight may fall during prolonged intestinal signs.

Nausea may cause lip licking, drooling and loss of appetite. A dog in pain may whine or stretch the forelegs down while keeping the hindquarters raised. These additional signs help distinguish simple gas from abdominal disease requiring investigation.

Complications and consequences

Diet-related gas can often be controlled with dietary changes if no underlying disease is present. With ongoing weight loss or diarrhoea, the outlook depends on the underlying disease. Nutrient malabsorption can lead to weight loss and deficiencies.

Severe distension can stretch the intestinal wall and cause pain. With obstruction or loss of intestinal movement, fluids and electrolytes can accumulate inside the intestine. Severe circulatory failure and shock concern these ill, distended patients rather than ordinary occasional farting.

Diagnosis at the vet

Diet and other signs guide investigation

Your vet reviews food, treats and the timing of signs in relation to meals. The dietary history may suggest poor tolerance of an ingredient or eating unsuitable material. Examination includes looking at and feeling the abdomen for distension, tenderness or a mass. Stool amount, colour, consistency and any blood or mucus help locate intestinal problems.

With weight loss and diarrhoea, possible systemic diseases are investigated alongside malabsorption. Pancreatic enzyme function can be assessed with blood TLI measurement. Cobalamin, or vitamin B12, and folate levels can provide information about small intestinal function. Folate is absorbed particularly in the middle small intestine and cobalamin in the final part. A confirmed deficiency may need vitamin supplementation alongside treatment of the underlying disease.

Basic investigations for prolonged diarrhoea and weight loss may include a blood count, biochemistry, urinalysis and a faecal sample. Biochemistry and urinalysis help exclude systemic diseases causing chronic diarrhoea.

Imaging and biopsies follow the findings

X-rays can investigate suspected obstruction. Ultrasound examines intestinal wall thickness, tumours, foreign bodies and lymph nodes. Persistent intestinal disease may require endoscopy and lining biopsies. These investigate conditions such as inflammation or an intestinal tumour.

If your dog is eating and stable, a planned dietary trial may precede intestinal biopsies. If signs resolve with a treatment trial, intestinal biopsies are generally not justified. Dietary changes for gas alone are selected on different grounds from investigations for a dog losing weight or having diarrhoea.

Treatment

Good digestibility leaves less material for bacteria

Highly digestible, low-residue food can reduce the material left for colonic fermentation. Protein digestibility in low-residue food may exceed 87%. The target digestibility for fat and carbohydrate in such diets is over 90%. They generally contain less than 3–5% fibre on a dry matter basis.

When planning a dietary trial to reduce odour, a protein content no higher than 30% of dry matter may be considered. Changing the protein source can also help. A rice-based carbohydrate source may produce less gas than a wheat- or maize-based alternative. Reducing fat content from the previous diet may benefit some dogs.

The diet must still meet your dog's nutritional needs for their life stage. Home-made chicken and rice is not a balanced long-term diet. Long-term home feeding needs a plan from a vet with nutritional expertise.

Food-related signs can be investigated with a novel-protein or hydrolysed diet trial. In hydrolysed food, protein is broken into smaller peptides, reducing its ability to trigger an immune reaction.

Fibre fermentation also produces short-chain fatty acids called butyrate, propionate and acetate. They may support the intestinal barrier and reduce inflammatory signalling. Psyllium holds water and may improve stool consistency. Fibre is therefore assessed on more than gas production alone.

The crude fibre percentage on packaging does not include soluble fibre and may underestimate total fibre. Excessive soluble or insoluble fibre can cause loose stools, constipation or gas.

Slower eating reduces swallowed air

Dividing the daily ration into smaller meals may improve digestibility and reduce gas. A slow-feeder bowl or food activity toy can slow gulping. In homes with several dogs, separate feeding places may reduce perceived competition. Gentle outdoor exercise within 30 minutes of eating may encourage bowel movements and gas passage.

Supplements do not replace investigating the cause

Probiotics contain live microbes whose health benefit must be demonstrated for that particular strain. Prebiotics are indigestible nutrients that modify the activity of bacteria already in the intestine. A synbiotic combines a probiotic and a prebiotic.

Supplement effects depend on the product and microbial strains it contains. Some products have been found to contain fewer live microbes than stated. Increased flatulence or looser stools can be adverse effects.

Confirmed exocrine pancreatic insufficiency is treated with digestive enzyme replacement. Chronic intestinal disease may require other veterinary-selected treatments as well as diet. Any medication is prescribed by your vet based on investigation results.

Prevention

Suitable feeding depends on nutritional needs for your dog's life stage and individual tolerance of the food. The ingredient list does not directly establish nutritional quality. Alongside ingredients, assess the overall nutrient profile and how your dog does on the food.

Small meals and calm feeding reduce how much food is gulped at once. Avoiding table scraps and very fatty extras may prevent digestive signs. Fibre supplements are selected by their effects, because vigorous fermentation can increase gas.

Important for dog owners

Record food, treat and supplement quantities and when signs began. Separately note farting frequency, smell, abdominal rumbling and stool quality. Weigh your dog regularly so weight loss becomes apparent. Bring food packaging details to the appointment and mention treats given by other family members.

Agree with your vet which dietary change to try and when to assess its effect. Clearly record changes in your diary so the timing of food and signs can be compared. Report vomiting, diarrhoea, refusal to eat or weight loss promptly if these develop alongside gas. A suddenly swollen, painful abdomen with unproductive retching needs emergency assessment.

Frequently asked questions

Is farting normal for dogs?

Gas production and passage are normal bodily functions involved in digestion. The quantity varies between dogs. Increased farting can relate to gulping food or food digestibility. However, gas with diarrhoea or weight loss needs veterinary investigation.

Why do my dog's farts smell bad?

Most gas leaving the intestine is odourless. Sulphur compounds, such as hydrogen sulphide, are particularly responsible for smell. Food remaining for colonic bacterial fermentation influences gas production. A highly digestible diet may reduce the material available to these bacteria.

Can a fibre supplement worsen flatulence?

Rapidly fermentable fibre may increase gas production. However, not all fibres work in the same way. Some more slowly fermentable fibres hold water and increase stool bulk. Fibre selection therefore also considers stool quality and other digestive signs.

Should I give my dog a probiotic for gas?

Potential probiotic benefit depends on the microbial strain and the problem being treated. Some products may also initially increase flatulence or loosen stools. Prebiotics can increase gas through intestinal bacterial activity. The need for a product is assessed alongside diet and possible intestinal disease.

When should I worry about flatulence?

Diarrhoea, weight loss or poor appetite alongside flatulence warrants an appointment for investigation. Sudden abdominal swelling and repeated unproductive retching may indicate gastric dilatation and volvulus. A situation consistent with this always needs immediate veterinary examination and treatment.