rat or mice

The picture isn't quite clear enough to me, but with the thickness of that head and paws relative to the body, it's possibly a weaned rat? Whether rats are born grey or not, they're already white by the time they're weaned (40g).

A mouse at 40g would be retired breeders, and those look like huge bodies with tiny heads and tiny paws.

That's some weird kind of rat or mouse. I breed mice, rats and ASF and none of them look like that one LOL.

You can feed anything they will eat, rats, mice, African Soft Fur rats, chickens, Guinea pigs, goats, etc... Any small animal will do. I prefer to feed a variety to all my snakes. It takes more time to feed multiple smaller meals but it still does the trick. Some snakes prefer one food item over another, most will eat just about anything.

I think that rodent may actually be a 'Dagu'?

http://www.sandsexoticanimals.com/care/degu-care.jpg

A degu is a small rodent that is closely related to the guinea pig and chinchilla.