Our products are formulated to have similar nutrient profiles, so they provide an excellent opportunity for rotating proteins. (Vet recommended that every 3 months, rotate to different proteins) By transitioning between fish and meat, you are exposing your dog/cat to a wider variety of nutrients and potentially lessening the chance for allergies, digestive issues, or food intolerance to develop from eating the same thing over and over. When you feed one diet continuously, you can limit the types of these beneficial microorganisms. While it's perfectly safe to stop feeding your cat/dog's previous food one day and introduce (insert brand) the next, we recommend a gradual transition for up to two weeks, especially if your dog/cat was eating a high-grain, Corn, Wheat, Soy diet, or has food sensitivities. This makes it easier for your pet's system to acclimate to the new food. Pets generally love the variety of proteins, especially if they're picky eaters.