Safe wood / treatment for dog crate shelf?

Since I've got no DIY equipment I'm looking into having a shelf made up, the problem is I don't know which woods and wood treatments are suitable! I've tried searching the forums and Googling but I can't seem to find a definitive answer. Can anyone help? :?

I used exterior (sometimes called wpb grade) plywood but others have used MDF. Personally I'd avoid chipboard or waferboard.
Indoors you don't need a treatment but Cuprinol Garden Shades is a safe bet if you do want to use one.

Mike

Pets at home do a tin of wood stain for rabbit hutches maybe you could try that, its a bout 4.00 a tin and comes in 2 different colours

I used exterior grade 9mm plywood for the levels in my bunnies' mansion. But left it untreated and covered it in self adhesive lino planks and carpet to protect it.

I wouldn't use mdf as the dust and glue probably isn't very good for bunnies if they chewed on it.