I just took our stinky dog to the vet and talked about his nighttime gas, among other things. I posted earlier that he is diabetic and has other problems related to his age of 11 or 12.
Due to his diabetes, he is on a high fiber, high protein diet. The food we use is OK, it's not the most expensive food. The vet said that one thing that causes that gas is a poor fiber source. She recommends that the fiber ingredient in the food be beet fiber, not rice, as is most commonly used. She said the rice isn't digested as well. The dog is having his teeth cleaned soon, so she said not to make any changes right now--we want to be sure that his diabetes stays stable. But, I'm going to do some research in the meantime and see if we can find something affordable as well as appropriate. Will keep you informed.