All mammals produce intestinal gas, and dogs are no exception. Compared to cows, which produce upward of 60 quarts of gas a day, dogs are relatively modest in their output. What they lack in quantity, however, they make up for in pungency - their gas is unusually smelly. Even a small dog can clear a large room, and bigger dogs, especially those who are real food-hounds, can be downright unpleasant to be around. Part of the reason we notice dogs' gas so much is that dogs haven't been taught to hold it in. They don't go out of the room to pass it.

The intestinal tract is filled with bacteria that help process foods and aid in digestion. As part of their natural metabolism, the bacteria release clouds of sulfurous gases, which gives intestinal gas its unpleasant smell. The more protein there is in the diet, the stronger the smell.

Cows and other herbivores produce a lot of gas, but there isn't enough meat-based protein in their diets to create large amounts of sulfur gases. Dogs, on the other hand, eat a lot of protein - quite a bit more than most people. They don't necessarily have a lot of gas, but when they do, it's powerful stuff.

It's not only protein that contributes to high-octane gas - it's also the type of protein. Many commercial dog foods get their protein from animal by-products; feathers, for example, or ground-up bone. These ingredients are harder for dogs to digest than protein that comes from "whole" foods, such as chicken meat or eggs. The harder the body has to work to process protein, the more flatulent a dog is going to be.

A surprising number of dogs are sensitive to ingredients in their food. For example, milk is a

common ingredient in dog food, but many dogs have a condition that makes it difficult for them to digest it. This condition, called lactose intolerance, can make dogs extremely gassy.

Food allergies are another problem. Dogs who are allergic to ingredients such as soy or wheat aren't able to digest their food efficiently and tend to be gassy. They often get diarrhea as well.

One way to tell if your dog is sensitive to something in his diet is to write down every single thing he's had to eat within the 24 hours preceding the gassy episodes. Sometimes something as simple as switching to a different brand of treats will make intestinal gas a little less unpleasant. Your veterinarian may recommend putting your dog on a diet called an elimination diet. He'll be given a hypoallergenic food containing ingredients he's never had before. If the gas goes away, you'll know that something in his food was causing it.