First, most chinchilla breeders use some sort of rabbit feed. That said, the first thing you need to do is find out WHICH will be available to you easily...and consistently. Talk to whomever you intend to purchase from. Make sure you'll always be able to purchase THAT feed. After that, it's all about comparing nutritional values. As mentioned, there are more than enough threads on this forum to tell you which are the most popular feeds. I've successfully used Blue Seal Show Hutch Delux (which is an extruded pellet) as well as Manna Pro Pro and Manna Pro Sho. Best of luck!