Hello, our 3 year old has become very fussy now during mealtime. We recently changed their food. Our older dog doesn't seem to mind it and eats it all. It's been very hot and I know I don't like eating a lot when it gets like this. Could this be why he won't eat? Is it because we changed the food? How long can he go without food? Don't know what to do with our little guy. Thoughts, advice is appreciated.