Corn goes right through our bodies and does the same for dogs. Biproducts are every single part of a chicken including intestines, claws, and beaks. Pedigree is a very unhealthy food. It is like feeding your dog McDonald everyday. You can take a look at https://www.dogfoodadvisor.com/ to get a 1 – 5 star rating on the food.
Once you get the new food, for the first day just add a small amount in your fingertips, then a little bit more for the 2nd day. On the third day add 1/4 cup for each feeding if the dog is big enough for that much. Just keep adding a little bit more each day until you are adding more of the new food.
If your dog is not reacting well to the new food then you will notice their stool is loose, mushy, or runny. They may also have a lot of gas. When you are switching food, it is trial and error.
If your dog has allergies, there are plenty of times that chicken causes more allergies then beef, lamb, or fish. Within my 20 years of dog training, I have learned that light colored and white dogs have more food and environmental allergies then darker colored dogs. I find that foods that have fish and limited ingredients works best for dogs with allergies but I am not a veterinarian.
All dogs are different, so it may not affect their belly but why take the chance. Unfortunately, the Coronavirus has caused people to have to switch to a less expensive food and that is ok. My only suggestion is to switch to a food that does not have corn and biproduct meal.
Please do not quickly switch from one brand of food to another because it may cause severe diarrhea!