That's really great news. My guess is that he's a picky eater and the first kibble had really low quality ingredients. One week without food is pretty scary though. Over here, one day sans food would scare me, but every dog is different. Have you ever fed him green tripe? That might be a handy thing to have if you ever need to coax him to eat his kibble. Most dogs go bonkers for it. It's really stinky and flavorful and super nutritious.