If the old cat food is not too much when changing the cat's food, you can feed a little less of the new cat food first. It is best to feed it with the canned food and snacks that the cat usually likes to eat, so that the cat can accept it more easily. If the cat is not used to the sudden change of food, it may irritate the gastrointestinal tract. If you find that the cat has adverse reactions, you need to stop immediately and switch to the old food. If the cat can accept a little feeding and slowly increase the amount of new cat food, it is better to have a transition period of more than a week.