[jabberwock]

We have a wooden outside run - we used wood treatment from Auro - their water based stains and finishes are suitable for childrens cots and toys (which certainly get chewed by babies). But because it's an outdoor run and there is unlimited grass available the piggies have never once tried to nibble the wood. It might be different for an indoor cage but you can always put a Correx liner in a wooden frame - you can get Correx on ebay.