Being the owner of both a boxer and a bulldog with flatulence, Claudia Kirk, DVM, DACVN, DACVIM, a professor at the University of Tennessee College of Veterinary Medicine, can relate to the challenges excess flatus provides to pet owners. Episodes of flatus make living in close quarters with pets less than enjoyable, especially when the foul odor is enough to clear a room.
Flatus, a byproduct of bacterial fermentation, often results from dietary causes—highly fermentable fiber, indigestible carbohydrates, dietary indiscretions or a sudden diet change, Kirk says. Plus, some breeds seem to be predisposed to the condition, with boxers, bulldogs, Boston terriers and other brachycephalic breeds among the most notorious.
Aerophagia: yes or no?
Kirk says she sees increased intestinal gas in dogs with aggressive or competitive eating behaviors, which promote aerophagia. Dogs that “wolf” their food down may burp, have borborygmi and possibly experience increased flatus because of large amounts of swallowed air. However, aerophagia alone does not cause the odiferous flatus that is so objectionable to owners, she says.
Dottie Laflamme, DVM, PhD, DACVN, a nutritionist with Nestlé Purina PetCare in St. Louis, says she hasn’t seen evidence to support the idea of aerophagia as a contributor to flatulence. Air coming in may cause a dog to eructate, or burp, but the suggestion that the air moves down the GI tract to the lower bowels to cause flatulence is open to question. “There is some evidence in regard to aerophagia and bloat, but intestinal gas is really a different phenomenon,” Laflamme says.
Jillian Haines, DVM, MS, assistant professor of small animal internal medicine at Washington State University College of Veterinary Medicine, agrees. “One study looked at dogs to observe how quickly they ate their food, how ‘greedy’ they were,” she says.1 “This greedy consumption did not appear to affect whether or not they would become flatulent. We think it might be a contributing cause, but we have to wonder why they are not able to eructate the gas normally. They should be belching, not expelling the gas anally unless there is something else going on with their stomach or further down the GI tract causing fermentation in the lower bowel. We don’t really know.”
The most common dietary sources for flatus formation are indigestible carbohydrates, especially soluble and fermentable fibers, and less-digestible meat products. High-meat products in particular can cause foul-smelling gas due to higher levels of indoles, phenols and sulfur derivatives. Here are some other specific dietary ingredients, physiological conditions and behavioral tendencies that may promote flatulence in dogs:
> Food allergies. “A very high percentage of dogs that have food allergy or food hypersensitivity have flatulence as a sign,” Haines says. “Putting them on highly digestible, novel or limited protein diets does not necessarily stop that problem. It might in some cases, but it does not necessarily do so.”
> Beans. Soybeans and other bean meals are often suggested as a cause of flatulence in people and dogs. However, allowing the gut to adjust to any given diet—with or without soy—will reduce the predisposition for gas production, whereas sudden dietary changes can increase gas in some dogs, Laflamme says.
> Dietary indiscretions. Dogs that get into the garbage, raid the cat food or cat box, or surf the local pasture for “horse nuggets” are at greater risk due to GI upset or consumption of fermentable substrates, both of which are associated with flatulence.
> Table scraps. “One always has to look at table scraps, Haines says. “Owners must not forget that their dogs may be lactose intolerant, therefore a piece of cheese might be a potential source of gas.” Joe Wakshlag, DVM, PhD, DACVIM, DAVCSMR, associate professor of clinical nutrition at Cornell University College of Veterinary Medicine, agrees. He recommends that owners curb table foods and treats to 10 to 20 percent of total energy intake and consider treats that are complete and balanced in their nutritional makeup.
GI-associated illness and flatulence
Certain medical disorders will also increase the risk of flatulence. “When a patient has a GI disorder that involves malabsorption of nutrients in the intestine, those malabsorbed nutrients act as substrates for fermentation in the colon,” Kirk says. “That will lead to both gas production as well as increased odor.”
For example, boxers and French bulldogs are predisposed to histiocytic ulcerative colitis, Haines notes.2-3 “We suspect it’s due to an invasive E. coli infection that responds to treatment with enrofloxacin,” she says. “A change in the bacterial microflora in the colon may affect gas production as well, and the gas could potentially worsen the condition.”
Another disorder that causes malabsorption is inflammatory bowel disease (IBD). Any breed can experience IBD, but some are predisposed to the condition, including Wheaten terriers and Yorkshire Terriers.4 Haines says that with IBD, the GI tract is infiltrated with inflammatory cells such as lymphocytes and plasmacytes. The inflammation leads to alterations in intestinal contents and disruptions of normal microflora, potentially causing bacterial overgrowth, which affects the intestine’s ability to absorb nutrients normally. But does all of this cause gas?
“At least from a clinical perspective, flatulence is not one of the major clinical signs we see in these dogs,” Haines says. “At least it’s not one of the most concerning signs, as opposed to weight loss, vomiting, diarrhea, inappetence and protein loss—those are the things we really worry about.”
When gas is a result of IBD, however, “treatment of the underlying disease will likely be needed to resolve the flatulence,” Haines says.
“Parasites, small intestinal bacterial overgrowth and canine parvovirus infection may also cause flatulence by the same method of disturbing the normal ability of the intestine to absorb nutrients,” Haines says. “Antibiotic use could also affect the microflora, leading to flatulence.”
When Haines is presented with a dog with excessive foul flatulence, she first looks for an underlying cause based on history and physical exam. “Animals that have abdominal pain or distention, vomiting or other signs of illness are more likely to have an underlying GI disease,” she says.
Haines’ team uses GI imaging—often ultrasound—as well as blood tests to look for conditions such as exocrine pancreatic insufficiency (EPI), IBD or pancreatitis. Tests she relies on include serum trypsin-like immunoreactivity (TLI) to assess for EPI and canine pancreatic lipase immunoreactivity (cPLI) to assess for pancreatitis. Her team may also test serum cobalamin and folate concentrations to check for evidence of disease in the small intestine, either from bacterial production of folate or decreased absorption of cobalamin. She says endoscopic or surgical biopsies are often needed to further evaluate for IBD.
“There are potentially some motility disorders that could cause flatulence,” Haines continues. “These may show up on ultrasound or on radiographs, but some can be very difficult to definitively diagnose.”
If Haines and her team don’t see any evidence of GI disease, they turn to medical management of the flatulence. There are few medications available to treat flatulence, though one study looked at a combination of activated charcoal, yucca and zinc acetate.5 “That seemed to help with the hydrogen sulfide gases, the ones that are particularly malodorous, which obviously affect the owners,” Haines says.
Laflamme says there are several nutritional approaches veterinarians and pet owners can try to decrease flatulence. “Changing the microflora or changing the type and amount of nondigestible foodstuffs entering into the large intestine may have an effect,” she says. “Anytime we change the diet in any way, shape or form, a byproduct is going to be a change in the GI microflora. We can selectively look for dietary changes that will induce a positive change as opposed to a negative change.”
Haines calls this area a medical “gray zone.” “We often think we’re on top of things, but sometimes we’re not,” she admits. “We have long talked about the nondigestible oligosaccharides in some foods like soy products. However, when a study looked more closely at soy products,6 they actually found that those oligosaccharides didn’t appear to be the cause of flatulence.”
Still, she says, her team takes a careful diet history and often recommends a change to a lower-fiber, more digestible food. “It doesn’t have to be excessively low, just lower in fiber than the current diet,” Haines says.
“Some of the intestinal [therapeutic] diets can be helpful—though one has look at them carefully, as sometimes the fat content can be too high for the individual pet,” Haines adds. “Novel protein or hydrolyzed diets are a good choice because a dog with flatulence may have food allergies [or hypersensitivity] as an underlying cause. Some commercial canned diets might contain guar gum or resistant starches that contribute to flatulence. One has to be very cognizant of what’s in the diet.”
Wakshlag says solving the flatulence problem requires both substrate utilization and changing the microflora at the same time. “Protein that escapes digestion is thought to be one of the major substrates for clostridial bacteria,” he says. “Those bacteria tend to utilize it and/or break it down, and when that happens you get the more malodorous flatulence. The thought is that the protein maldigestion will cause the malodor, but in the end anything that causes fermentation (e.g., soluble fibers) will cause a lot of gaseous emissions to occur.
“If you’re trying to decrease flatulence, I would definitely not be prescribing a high-soluble-fiber diet,” Wakshlag continues. “I’m also probably going to moderate the protein to some degree. It depends on the individual dog, what that dog is eating, his disease condition, and what you’re trying to mitigate within that particular animal. If the protein is the problem for a patient, we’re looking for increased protein digestibility. So in general, if flatulence is problem, one is looking for the most digestible diet.”
Prebiotics and probiotics
Laflamme emphasizes that flatulence is an individual and somewhat idiosyncratic response. “You have to find the diet that works for the individual dog, and because we know it’s the microflora causing the gas, prebiotics, probiotics and moderate-fiber diets may have a positive effect,” she says. “Sometimes a veterinarian will suggest a highly digestible diet as a way to reduce the flatulence, but another approach would be a ‘lite’ [low-calorie] or moderate-fiber diet. These diets will have a prebiotic effect. They provide substrate for the beneficial microflora, enhancing their numbers and reducing the gas.”
A recent paper presented at a European Society of Veterinary and Comparative Nutrition conference noted a statistically significant reduction in flatulence associated with a probiotic treatment.7 “In theory, you’re altering the microflora that is producing the gas,” Laflamme says.
Despite absence of evidence of effectiveness, decreasing the amount of air swallowed may help some dogs. Owners can also look for ways to decrease stress associated with eating. “Allowing a predisposed dog to eat by itself in a quiet place lowers excitement while eating,” Haines says. “Competitive eating is a potential problem, so ensure there are no other dogs around to incite the dog to eat more quickly and gulp more air.”
Feeding smaller, more frequent meals can also decrease the amount of air that dogs swallow, and so can mixing dry and canned food, Haines says. With brachycephalic breeds, surgery to correct such conditions as an elongated soft palate or stenotic nares can help alleviate aerophagia.
Exercise should also be recommended. One survey of pet dogs showed that those that received the least amount of exercise had the greatest problem with flatulence, Laflamme notes.1 “If one has a dog that has a problem with flatulence, get them out for exercise and to evacuate his bowels regularly,” she says. “That should help to reduce the gas problem as well.”
Haines agrees. “Active dogs or those that get more exercise are noted to have less flatulence,” she says. “We don’t know if the timing of exercise matters—possibly after meals, though it’s hard to say.”
No matter the cause, whether it’s dietary issues or potential GI disease, flatulence in a dog can create real problems for its owner. Plus, if the condition is severe, “it can make the dog quite uncomfortable as well,” Kirk says.
Hopefully these pet owners will work with their veterinarian to treat the dog and solve the problem, not forfeit a favored companion that can’t help releasing choking clouds of malodorous gas. Veterinarians who persist in finding a solution help ensure that their patient remains in the home and is not sent to a shelter for a behavior it can’t control.
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2. Manchester AC, Hill S, Sabatino B, et al. Association between granulomatous colitis in French Bulldogs and invasive Escherichia coli and response to fluoroquinolone antimicrobials. J Vet Intern Med 2013;27:56-61.
3. Craven M, Mansfield CS, Simpson KW. Granulomatous colitis of boxer dogs. Vet Clin N Am Sm Anim Pract 2011;41:433-445.
4. Dossin O, Lavoué R. Protein-losing enteropathies. Vet Clin N Am Sm Anim Pract 2011;41:399-418.
5. Giffard CJ, Collins SB, Stoodley NC, et al. Administration of charcoal, Yucca shidigera, and zinc acetate to reduce malodorous flatulence in dogs. JAVMA 2001;218:892.
6. Yamka RM, Harmon DL, Schoenherr WD, et al. In vivo measurement of flatulence and nutrient digestibility in dogs fed poultry by-product meal, conventional soybean meal, and low-oligosaccharide low-phytate soybean meal. Am J Vet Res 2006;67:88-94.
7. 16th ESVCN Congress, Poland, Septempber 2012.
1. Roudebush P. Flatulence: Causes and management options. Compend 2001;23:1075.