I don't know the official, veterinary answer to this question. I have always rotated my dogs' food, intuitively I guess. What I do is buy a 12 -15 lbs. bag of kibble and as that bag is almost empty I buy another with a different protein source. Since I always add canned food to the kibble, I buy as many different protein sources as I can and rotate those. I also feed organ meats, sardines canned in water and canned mackerel. In short, as varied a diet as possible.