Oh, well now I feel a bit silly. I know everyone is trying to help.
I guess it's hard not to imagine how the op must feel after posting three times in the last five weeks trying to get help and not getting any specific advice. Yeah I agree with everybody it's frostbite. Probably the roo rested its good foot on the ground where it's colder instead of under himself and got stuck in that position. The photos from her first (?) post seem to show concrete floors. That would be enough. Or he may have gotten frostbite before the snows set in. Either way it's frostbite. The op says the foot smell rotten, is sometimes pussy, and is hot to the touch. The roo needs antibiotics. I know nothing about dosing antibiotics.