Switching my puppy from Nutro to Natural Balance?

I agree you should try a change in his food. Be sure you do it slowly, mixing both foods and adding more and more of the new until the change is done. I do not use any of the above, so I won't comment on that...I just wanted you to be aware that burping and farting can also be a sign that your dog is eating too quickly or taking in air as he eats. If you have a raised platform to keep his food bowl, it will put his head in a better position for him to feed. If he does eat quickly, you can slow him down by feeding him smaller increments in the same sitting. (I use Nature's Recipe farm stand selects...the one with the main ingredient being turkey...use senior formula for the old girl and have been doing well with both...) I also started on Nutro and switched....good luck with your pup!