Passing gas is a normal bodily function but you may wish to address the fact when the farts seem to be excessive or very stinky. A foul-smelling fart is an indication that some food has not been properly digested and is fermenting inside the body. The smell of fermenting food is what causes smelly farts. Try feeding your dog yoghurt to prevent smelly farts. Although yoghurt is a dairy food it has different properties to milk and cheese. Yoghurt has good bacteria and can be very beneficial in treating excess gas. Feed two to three tablespoons of plain, organic non-fat yoghurt a day.