[Stephen Tucker]

While eating dinner with a friend last weekend, her 75lb mastiff began to have some rather noticeable flatulence issues.  My friend claims that this is normal, as despite the fact that her dogs (the other is a chihuahua) are well-fed, exercise regularly, etc., it is just something dogs do.  I've never noticed my cats contributing similar smells to my surroundings.  Why do dogs pass gas more noticeably than cats? 

...It can't be all down to size, as both of my cats are larger than her smaller dog, and her little one is definitely not flatulence-free.
...If it makes a difference, all four of our pets are on grain-free diets.  My cats eat wet and dry food, while her dogs eat only dry food.  My cats are indoor-only and her dogs never go outside unsupervised and are usually on their leashes.