Gas (Flatulence) in Dogs

My dog has excessive gas. What is this called?

The excessive formation of gas in the stomach or intestine is referred to as flatulence. Flatus is the medical term used to describe air or gas expelled through the anus. Most flatulence consists of odorless gases; the odor comes from sulfur-containing gases like hydrogen sulfide.

Belching, borborygmus, and gas can occur normally in dogs, but if they become excessive, there may be an underlying issue that requires medical attention. If these signs develop along with weight loss or diarrhea, it is likely that something serious is happening in the GI system, and you should visit your veterinarian.

What causes gas in dogs?

Flatulence comes from an abnormal amount of gas in the gastrointestinal (GI) system. It can be due to swallowed air or abnormal gas production from the biome (GI bacteria) that may occur in response to illness or to something ingested, such as a change in diet or eating spoiled food.

Dogs with underlying breathing issues tend to swallow more air, including brachycephalic dogs (dogs with squished faces) such as bulldogs, pugs, French bulldogs, and Boston terriers; dogs with tracheal collapse or other airway issues, and dogs with heart disease. Exercise and eating too fast can also increase air swallowing.

"Overweight, obese, and sedentary dogs are at higher risk 
for developing chronic flatulence, regardless of diet."

In the GI tract, colon bacteria break down (ferment) carbohydrates and certain fibers, creating gas. A poorly digested diet causes excessive fermentation in the colon and subsequent gas formation. Soybeans, peas, beans, milk products, high-fat diets, and spicy foods are all commonly associated with flatulence in dogs.

Most dogs and cats are lactose intolerant and experience flatulence and/or intestinal upset if they are fed milk or dairy products. A dog that is fed a premium diet and still experiences flatulence should be tested for a problem with either poor digestion or poor absorption of nutrients from the diet. Overweight, obese, and sedentary dogs are at higher risk for developing chronic flatulence, regardless of diet.

What are the clinical signs of flatulence?

The most common clinical signs of flatulence include expulsion of gas from the anus, with or without odor; mild abdominal discomfort; mild stomach distention or bloating; and excessive gaseous sounds or rumbling from the abdomen (borborygmus).

If the dog has an underlying gastrointestinal problem that causes an inability or impaired ability to absorb nutrients for the body, clinical signs will also include loose stools or diarrhea, vomiting, and weight loss.

How is the cause of flatulence diagnosed?

Diagnosis is based on medical history and clinical signs. Some of the common causes that must be ruled out include:

• Increased swallowing of air (aerophagia)
• Gluttony or compulsive eating
• Respiratory disease
• Feeding shortly after exercise
• Brachycephalic or flat-faced breeds
• Dietary indiscretion
• Diets high in soybeans, peas, or beans
• Diets high in fermentable fibers such as lactulose, psyllium, or oat bran
• Spoiled food
• Milk and dairy products
• Sudden change in diet
• Spicy foods and food additives
• Inflammatory bowel disease (IBD)
• Small intestinal bacterial overgrowth (SIBO)
• Tumors
• Irritable bowel syndrome (IBS)
• Intestinal parasites
• Enteritis
• Exocrine pancreatic insufficiency (EPI)

Diagnostic tests may include fecal examination and/or culture; rectal cytology; blood and urine tests, including specialized tests such as trypsin-like immunoreactivity (TLI), serum cobalamin, and serum folate tests; abdominal X-rays; abdominal ultrasound; and intestinal biopsies.

How is flatulence treated?

Treatment is based on diagnosis and commonly involves a change in diet. Recommendations include changing to a diet that is highly digestible, with low fiber and fat, reducing the amount of food that needs to be digested and absorbed before reaching the pet’s colon.

• Foods that use rice as the carbohydrate source may generate less gas than foods that rely on wheat or corn.
• Changing your dog's dietary protein source may also help (e.g., switching from a food that contains corn, chicken, and soybean meal to one with lamb, rice, and barley). Dry matter protein content should not exceed 30%, and soy protein should be avoided for dogs with offensive gas.
• Fiber may play a significant role in producing excessive gas in some dogs. Soluble fibers like fruit pectins are easily broken down by GI bacteria and can significantly contribute to excessive flatulence and gas. Mixed soluble and insoluble fibers can also contribute to the problem. It may be best to limit fiber to 5% dry matter (DM) or less.
• Vegetarian dog foods may be problematic because they likely include sulfur-containing vegetables and legumes, such as peas and lentils, which promote gas production.
• Certain ingredients may contribute to the problem, including beet pulp, bran, fruits, high-fructose corn syrup, pea fiber, pectin, psyllium, soybean hulls, and soy fiber.

If the major ingredients in your dog’s food are potential gas contributors, look for a nutrient profile that avoids these items. There are several therapeutic nutritional formulations currently available to support optimal GI health and address adverse food reactions. One of these nutrient profiles may eliminate excessive GI gas in your dog. You may have to try a few different options to find the best food for a dog with objectionable flatulence.

Medical therapy may include probiotics (beneficial bacteria that aid digestion) along with prebiotics (food for the beneficial bacteria) to promote a healthy microbiome.

Small, frequent feedings are encouraged for dogs that eat rapidly or are hyperexcitable. Your veterinarian will outline a treatment plan designed specifically for your pet.

What is the prognosis for resolving flatulence?

Most patients with uncomplicated cases respond well to dietary and lifestyle changes. Once offending dietary substances and products are identified, it is important to avoid them.