My 6 year old Finnish Spitz has eaten Pro Plan beef since he was on solid food.  Since we switched to the new shredded blend on Christmas Day, we've noticed a distinct change in his eating habits.  He would avoid his food for a few days before eating it, and he was throwing up every few days.  He didn't act sick otherwise, though.  I finally realized that it must be his food and took him off of it 5 days ago.  Lo and behold, he's no longer throwing up and he's back to his old eating habits.

I won't be putting him back on this stuff, and I'm filing a complaint with both Purina and Petsmart...