[CockalierMom]

“The problem is that the puppy just wont eat her new food. I tried the 20% new, 80% old trick but she just picks the old food and eats, or even if by mistake she picks the new ones, just throws it out! ”

Listen to your puppy. When a dog does not want to eat a food they are telling you that something in it does not agree with them. Stay on the food that agrees with her and then if you are intent on changing foods, look for something with similar ingredients, fat content, fiber content and protein percentage.