It is always best to introduce any new food slowly over a period of around two weeks. This helps to avoid any unnecessary stomach upsets due to a sudden diet change.
Start by giving, for example, 80% of their old food and 20% of their new TP Feeds recipe. Gradually increase the amount of TP Feeds kibble given each day until they are enjoying 100% TP Feeds and reaping the benefits of these high quality recipes.
Of course, some dogs/cats can easily tolerate a sudden switch in their diet; you know your pet best, but this is the most sensible course of action. Many customers actually report that their dog/cat picks out the TP Feeds kibble and completely refuses to eat their old diet any more, thereby effectively choosing to switch over immediately anyway!