I think, perhaps nickmo needs to rethink his biology lesson. Fact is, chickens, like most avians, eliminate body waste through the same "vent" as that which the finished egg is laid. While it is true that the cloaca closes off when an egg is laid, the actual opening is the same. Birds, such the chicken only have one opening and don't have urine as such. It's mixed with the fecal material in the cloaca before exiting the body... The eggs never touch any of the waste material through the marvel of chicken construction...