Is it ok to change a puppys food more than once?!?

We breed German Shepherds, and we feed royal canin german shepherd formula, our dogs seem to do the best on it, but it is one of the more expensive brands, so I understand not wanting/not being able to feed it, but I would recommend it. You can change their food more than once, but do it gradually, and canned food may make your pup have diarrhea. Whichever food you do choose to feed, check the ingredients and make sure it has NO or VERY LITTLE corn in it. Good luck!