What happens if I have to suddenly change my Chinchilla's food?

Oxbow is a great food. Nutriphase is not. It may upset his stomach some, but he will be fine. Make sure to give plenty of hay and make sure he's pooping like normal. You may want to permanently keep him on Oxbow as it is one of the best chinchilla foods out there. If he doesn't eat it at first do not worry, he will get hungry and chins will not starve themselves! Do not put treats in it though. Chins are not guinea pigs or hamsters.