My puppy was fed 'Proplan' from the breeder but my friend who's breeding and doing shows recommended 'Eagle (Power formula)'. So I switched it to Eagle (it took about 1 week - mix half of previous kibble and half of new kibble) and my dog loves it and he's happy and healthy.
I thought I wanted to give him a bit more variety and tried a can food 'Puppy Chicken & Oat Bran Formula' mixed with kibble but he started having loose and very smelly stool and started throwing up badly. He threw up more than 10 times last night.
It was a sample from the lady who delievers Eagle stuff and I'm not planning to try the can food again. I learned that when my puppy is happy then he's happy. Never mess up with their diet when they are going well.