White vinegar will remove the calcium carbonateresidue from urine stains on floors, trays, and litter boxes.Don't know if it works well on rugs, though. Would test ahidden rug area before committing to a visible spot.
Mrs. Buck(Helen) has removed urine stains from our carpet successfullyusing Resolve carpet cleaner, but I don't know if it isavailable in your locale. Would imagine success rate has alot to do with the chemical composition of the individual rabbit'surine at any one given time.
Good luck! Keep us posted if you are able to find somethingthat works. We are all interested in that sort of information.
Buck