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The Science of Flatulence
There’s more to it than meets the nose!

As much as we might hate to admit it, flatulence is a normal biological function. A surprising amount of air is swallowed just with the simple act of eating, and if this is not burped out, it must exit through the other end. The amount of air swallowed tends to be increased when dogs feel they must eat quickly or in brachycephalic breeds (dogs with a compressed upper jaw and a short muzzle) that tend to breathe more by mouth than by nose.

Flatulence comes from an excess of gases in the intestinal tract. These gases may represent air that has been swallowed, gas produced in the biochemical process of digestion, gas diffusion from the bloodstream or gases produced by the bacteria that populate the intestinal tract. Contrary to popular belief, more than 99 percent of the gases that pass from the intestinal tract are odorless (whew!).

Dietary fiber in pet food is not easily digested by the pet’s own enzyme systems, but it is, however, readily digested by the gas-producing bacteria that live in the colon. As fiber is broken down here, hydrogen sulfide is produced, which is the cause of the really stinky gases. Therefore, a diet that is heavy in fiber further promotes a “happy environment” as well as “food” for the bacteria, ultimately producing more gas.   

Helping clear the air

Offering your pet a highly digestible, low-residue diet is one of the major ways to combat flatulence. A low-residue diet is designed to reduce the frequency and volume of stools, while prolonging transit time through the intestine. It is similar to a low-fiber diet, but includes restrictions on foods that increase bowel activity. Changing to a low-residue diet means that most of the nutrients of the food are digested and absorbed by the pet before they reach the colon, where the gas-forming bacteria live. Less food for the bacteria equals less bacteria, which equals less gas formed.

Sometimes just going through a case and/or bag of such a low-residue diet solves the problem and the pet can return to a regular food afterwards. If necessary, the therapeutic diet can become the pet’s regular food. Low-residue diets are available through your veterinarian, pet supply stores or can be cooked at home (boiled white rice, skinned chicken, cottage cheese and balanced with vitamins and minerals constitute low-residue ingredients).

Other easy changes that can help include:

  • Feeding smaller meals several times daily instead of one larger daily meal
  • Feeding a mixture of dry and canned foods
  • Discouraging rapid eating by placing an overturned small bowl inside the pet’s regular food bowl, preventing them from taking large mouthfuls
  • Avoiding soy, beans and peas in the diet
  • Avoiding any treats containing milk, cheese or other forms of lactose
  • Avoiding fresh or dried fruit treats
  • Avoiding canned foods containing the texturing ingredient carrageenan
  • Increasing activity: A sedentary lifestyle can increase the amount of gases produced as well as how long they “hang out” in the digestive tract. Activity increases gastrointestinal motility, which in turn expels gas and increases regularity of bowel movements.

Are there some medical conditions that can increase flatulence?

Changing the diet and ruling out actual intestinal disease are of primary importance in addressing flatulence. Some disease processes that can cause an increase in flatulence include:

  • Inflammatory bowel disease
  • Irritable bowel syndrome
  • Antibiotic-responsive intestinal disorders
  • Cancer
  • Parasites, viral or bacterial inflammation of the intestines
  • Food allergy or intolerance
  • Inadequate production of digestive enzymes by the pancreas

Medications and herbal and botanical supplements

Sometimes medication can help. Although there are many products available, most are unfortunately not as helpful as they are touted to be, or not labeled for animal use. There are more than 30 herbal and botanical preparations available to reduce gas in the stomach and intestines; however, the dosage, safety and efficacy are unknown.

If further therapy is needed, the following products have some basis and support that they may be of help for flatulence:

  • Yucca shidigera supplementation:
 Currently, this extract is labeled as a flavoring agent for pet food but it is also available as an oral supplement. Several studies have shown that it helps decrease the odor in flatulence.
  • Zinc acetate supplementation:
 Zinc binds to sulfhydryl compounds in flatulence ultimately serving to deodorize the gas.
  • Non-absorbable antibiotics: Such antibiotics kill the gas-forming bacteria of the colon and may be helpful as long as their use is not ongoing.

Some popular, but more questionable, products with regards to treating excessive flatulence include:

  • Probiotics: There are many ineffective probiotics being marketed and so it is important to use one that has been shown to contain live cultures that withstand stomach digestion. It is unknown if this type of product will really help in flatulence, as it is asking a great deal for these bacteria to survive the acid environment of the stomach, travel through the many feet of small intestines, and finally reach the colon in the attempt to displace the gas-forming resident bacteria. Still, these are unlikely to be harmful, and can be beneficial in other ways outside of the realm of flatulence, such as helping to stabilize the intestinal microenvironment.
  • Activated charcoal tablets: These tablets are not likely to be effective because the charcoal-binding sites are filled on the journey from mouth to colon, so by the time the tablet gets to the gas-forming large bowel bacteria, it has essentially already been used up!
  • Simethicone: This product may control the volume of gas produced, but not the odor. It is an antifoaming agent that reduces gas bubbles. This may be helpful at reducing our doggy’s gas discomfort, but not our nose discomfort.
  • Pancreatic enzyme supplementation: It is unlikely that these extra digestive enzymes would help a pet in the absence of actual exocrine pancreatic insufficiency. Furthermore, this treatment is relatively expensive for something that may only be slightly helpful.

While flatulence is a normal part of everyday life, if the problem persists or seems severe, it is recommended that you consult with your veterinarian. Even our pets sometimes need a smog check!

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Veterinarian Shea Cox has enjoyed an indirect path through her professional life, initially obtaining degrees in fine arts and nursing. She later obtained her veterinary medical degree from Michigan State University in 2001 and has been practicing emergency and critical care medicine solely since that time. In 2006, she joined the ER staff at PETS Referral Center in Berkeley and cannot imagine a more rewarding and fulfilling place to spend her working hours. In her spare time, she loves to paint, wield her green thumb, cook up a storm and sail. Her days are shared with the three loves of her life: her husband Scott and their two Doberman children that curiously occupy opposite ends of the personality spectrum.

CommentsPost a Comment
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Submitted by Marzocco's mum | June 25 2012 |

Ever since I switched my girl from kibble to raw diet mixed with Honest Kitchen she hardly has any gas. Its amazing what a difference!

Submitted by shirley zindler | July 21 2012 |

Thanks for the tips. Maybe be some genetics to it too. Of my four dogs, who all eat the same exact diet, one has worse gas. She's perfectly healthy and not elderly or brachycephalic either. I know some dogs are more sensitive to certain ingredients than others too. Any canned food in her dish is a recipe for evacuation.

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