While most people are all too familiar with the meaning of "gas" in companion dogs, the correct term for this condition is "flatulence." "Flatulence" is defined as the excessive formation of gas in the stomach or intestine that ultimately is released through the anus. Flatulence can occur in association with many digestive disorders. The rumbling sound caused by gas moving through the intestinal tract is called "borborygmus." It typically takes between 15 and 35 minutes for gas to move all the way through the intestines. When gases from the stomach are released through the mouth, it is called "eructation," more commonly known as burping.
Causes of Gas in Dogs
Gas is a normal component of gastrointestinal contents in all canines. The primary cause of intestinal gas is "aerophagia," which simply is the ingestion (or gulping) of air when swallowing. Gas also forms in the GI tract from the interaction of alkaline food (high pH), stomach acids and digestive enzymes; from bacterial metabolism and fermentation of digesta in the lower bowel; and from diffusion of gas out of circulating blood. Gas normally is removed from the gastrointestinal tract either up through the esophagus by burping (eructation; "belching"), or out through the anus by "passing gas") (flatulence; "farting" (slang)). Excess gas can be caused by a number of things, including:
Gastrointestinal disease. When dogs develop any form of malabsorption or maldigestion disorder, the undigested or unabsorbed food products remain available for fermentation by intestinal bacteria, which produces gas. Causes can include inflammatory bowel disease, gastrointestinal neoplasia (cancer), internal parasites, exocrine pancreatic insufficiency, small intestinal bacterial overgrowth, irritable bowel syndrome and bacterial or viral enteritis. Other diseases that cause an inability to break down and absorb nutrients can also cause flatulence, because the nonabsorbed material moves through the intestinal tract and becomes subject to abnormal fermentation in the lower bowel (also called the colon).
Excessive bacterial fermentation. Certain dietary substances are poorly digestible or poorly absorbable by domestic dogs, such as soy products, beans, peas, excess fat, spices, spoiled food, pectin and lactose. For example, adult dogs typically cannot digest foods that contain milk products, because as dogs mature they stop producing lactase, the enzyme necessary to break down lactose. As a result, adult dogs tend to become flatulent shortly after eating milk products. Diets that are high in fermentable fiber, such as oat bran, can also cause flatulence.
Excessive swallowing of air (aerophagia). Dogs that gulp their food – especially when multiple dogs are fed in the same area such that competition for food develops – tend to ingest abnormally large amounts of air when they swallow. Strenuous exercise, particularly when followed by gulping of food or water, can also cause a build-up of gastrointestinal gas. Finally, any respiratory disorder that causes rapid breathing can contribute to aerophagia in domestic dogs.
Dietary changes or indiscretion. Dogs often develop gas when their diets are changed, especially if those changes are not gradual. They also tend to be gassy after episodes of so-called "dietary indiscretion," such as when they get into the garbage, eat a bag of cat food, eat rotten or spoiled food, eat mice or other rodents or otherwise ingest things that are not part of a normal canine diet.
Prevention of Gas in Dogs
Canine flatulence can almost always be prevented, or at least managed. Some useful approaches include:
Change the diet. A highly digestible diet that is low in fat and fiber can decrease gastric gas production. Sometimes, changing the source of protein and/or carbohydrates in the diet can help a gassy dog as well. There are many high-quality dog foods – both in kibble and canned form – that contain novel protein or carbohydrate sources and that are highly digestible without containing high levels of fat or fiber. A veterinarian is the best one to discuss proper nutrition and dietary management for any particular animal.
Avoid milk products, soy products, beans, peas, high fat foods and spices.
Raised feeders. Many breeders, owners and veterinarians feed their dogs from raised feeders. Elevating a dog's food and water bowls is thought to reduce its intake of air when swallowing, especially in dogs prone to gulping their food. This subject is somewhat controversial, as there have not been sufficient repeatable scientific studies to prove the efficacy of feeding raised versus feeding at ground level in terms of managing intestinal gas.
Stones in bowls. For rapid-eaters, some experts recommend adding large rocks or stones to the food bowl, to force the dog to eat more slowly. Obviously, these stones must be big enough so that there is no way for the dog to swallow them.
Feed separately. Where competitive eating may be contributing to excess air gulping and gas formation, affected dogs should be fed separately from other household pets, in a quiet, private spot.
Avoid feeding after exercise. Owners should wait an hour or so after their dog has engaged in vigorous exercise before feeding a full meal.
Multiple small meals. It is usually better to feed a dog several small meals daily rather than a single large one, for a number of reasons. In addition to preventing the build-up of excessive gas (simply because there are fewer food products in the stomach available for fermentation at one time), multiple small meals are easier to digest and help regulate the digestive system. Many experts also believe that feeding a dog smaller meals more frequently can reduce its chances of developing gastric dilatation and volvulus, or "bloat."
Increased activity. Dogs, like people, usually benefit from an active lifestyle. Regular, low-impact moderate exercise stimulates motility in the gastrointestinal tract, which helps move gas along and regulates the passage of gas and feces.
Flatulence does not mean the passage of foul-smelling gas. It simply refers to excess gas formation in the GI tract that passes out through the anus. Most gastrointestinal gas is composed of oxygen, nitrogen, hydrogen, methane and carbon dioxide, all of which are odorless.
When excess gas forms in the stomach or intestine, it eventually has to be released through one end of the gastrointestinal tract or the other. The clinical signs of gas in dogs depend largely upon which end of the dog the gas is released from.
Symptoms of Gas in Dogs
Owners of dogs with gastrointestinal gas usually notice one or more of the following symptoms:
Audible passage of gas from the anus (with or without odor)
Rumbling sounds coming from the abdomen ("borborygmus")
Abdominal discomfort (usually mild)
Burping (belching; eructation)
A feces-like smell near their dog
Vomiting, diarrhea, weight loss, lack of appetite (may be present if flatulence is caused by underlying gastrointestinal disease)
Most natural gastrointestinal gas in dogs is odorless. The small amount that passes with a foul smell usually contains ammonia, indole, skatole, volatile amines, hydrogen sulfide and/or short-chain fatty acids. It can be caused by ingestion of cruciferous vegetables, onions, high-protein diets, endogenous mucin and bile acids.
Dogs at Increased Risk
Brachycephalic breeds, which are those with a very short, flat muzzle and a wide head, are predisposed to developing gastrointestinal gas, primarily because they swallow excess air while eating due to the unusual shape of their skull. These breeds include the Boston Terrier, Boxer, Bulldog, French Bulldog, King Charles Cavalier Spaniel, Pekingese and Pug, among others. Flatulence is also more prevalent in especially greedy eaters, because as they gulp their food they tend also to ingest a lot of air (called "aerophagia"). Some reports suggest that working and sporting breeds may be at an increased risk. Dogs that are especially nervous or finicky eaters, and those with a sedentary lifestyle, are also more likely to become gassy. Obese dogs are more likely to be sedentary and thus are also prone to flatulence.
Flatulence is not particularly difficult to diagnose. However, determining the underlying cause of excess gas production and release can be more challenging.
How Gas is Diagnosed
When a dog is presented for what the owner describes as "gas," most veterinarians will first take a thorough history of the dog's diet and dietary habits, including the type of food, amount fed at each meal, number of meals daily, additions or supplements to the diet, when the dog is fed, where the dog is fed and whether other pets eat in the same area at the same time. A thorough physical examination is usually the next step in the diagnostic process and will include gentle palpation of the abdomen to check for gas-filled loops of intestine, discomfort and/or distension. It is normal for a veterinarian to feel moderate amounts of gas in the intestinal tract. However, the dog may show mild to moderate signs of discomfort during the physical examination when excess gas is present.
The veterinarian usually will also auscult (listen to) sounds coming from the abdomen, using a stethoscope placed upon the abdominal wall. Normal bowel sounds are characterized by gurgling noises that vary in frequency, location, intensity and pitch. When the intestines are distended with gas, these sounds become hyper-resonant (richer and more intense) and can be heard over the entire gastrointestinal tract. Radiographs (x-rays) can also disclose accumulations of gas in the stomach and intestines.
Advance diagnostic testing is usually unnecessary if a dog is flatulent due to dietary or aerophagic conditions. If underlying gastrointestinal disease is suspected, the diagnostic protocols for those particular diseases should be followed and may include blood work, urine assessment, fecal evaluation, abdominal ultrasound, radiographic contrast studies and/or gastrointestinal biopsy.
Flatulence itself is not a disease, nor is it particularly a disorder in mild cases. It becomes problematic when it occurs frequently, when it becomes chronic, when it is malodorous and/or when it is accompanied by abdominal distension and discomfort.
When an owner notices that its dog is tender in the abdomen, is bloated or is passing excess gas (whether smelly or not), it probably is worth a call or a trip to the veterinarian. If the abdomen is extremely distended from gas accumulation, emergency treatment may be necessary to prevent or relieve a life-threatening condition called gastric dilatation and volvulus, also known as GDV, torsion or bloat. The therapeutic goals for dogs with excess gas are to eliminate abdominal distension, relieve gastrointestinal discomfort, identify and eliminate the cause of abnormal gas production and, if appropriate, reduce or eliminate the unpleasant odor associated with some cases of flatulence.
If a dog presents with severe abdominal distension and pain, the first course of action usually is to decompress the gastrointestinal tract. The veterinarian may attempt to intubate the dog by passing an orogastric tube through the mouth, down the throat (espophagus) and into the stomach, to provide an escape route for the gas. Unfortunately, sometimes the tube cannot be passed into the stomach. In those cases, and particularly if radiographs (x-rays) confirm GDV, the veterinarian may attempt to decompress the abdomen by a method called percutaneous trocharization. This involves inserting a large-bore needle through the skin and the abdominal wall directly into the stomach. This should allow the accumulated gas to escape through the needle, producing a hissing sound. If the dog has gastric dilatation and volvulus, emergency surgery almost always will be necessary.
A number of other medical treatments can help dogs with gas. Medications that relieve flatulence are called "carminatives." Some veterinarians recommend oral administration of activated charcoal, Yucca schidigera and zinc acetate – a combination which seems to dramatically decrease both flatulence and the unpleasant odor that often accompanies it. Other oral medications that may reduce gas and/or its foul aroma include bismuth subsalicylate and simethicone. It may be appropriate to administer pancreatic digestive enzyme supplements to dogs with excess bacterial metabolization and fermentation. Vitamin and mineral supplements can also change the acidity level and digestive activity within the gastrointestinal environment, which can help alleviate gas as well.
Alternative techniques that may benefit dogs with flatulence, in addition to medical treatment, might include: massage therapy to help alleviate gas accumulation and "move things along" through the gastrointestinal tract; possible application of acupressure techniques; use of herbal, botanical or other non-regulated supplements or homeopathic "remedies"; and other forms of supportive care that may help to ease discomfort and otherwise promote digestion, relaxation and comfort. Some of these adjunct approaches lack controlled studies of their proper dosage, safety and effectiveness and may not have established quality control methods or ways to assess their benefit to dogs with flatulence.
Once abdominal distension is relieved, flatulence in most dogs can be successfully controlled and managed with dietary modification and other preventative techniques. Some authorities suggest that owners of dogs with chronic flatulence make a point of keeping windows wide open and standing upwind of their dogs whenever possible.