When we switch our pet's food, it's best to do it gradually. You will want to start replacing roughly 20-25% with 'new' food increasing that amount slowly over a 7 to 10 day period until you have switched over entirely.
Since your pet is unique, there is no way of knowing before switching how they will react. Some of our pets are more tolerant than others. Being patient and watchful during a transition period is essential. While there could be some unwanted common side effects such as GI upset, the long-term effects of feeding a higher quality pet food will far outshine the short-term discomfort.
If during the process you have questions, like always, we are here to help.