[dancing spawn of ungoliant]

In the LotR "Weapons and Warfare" or what ever was the books name, they said that Saruman had some kind of breeding pits where the uruk-hai were born (?). I'm not quite sure , what that means nor I know how that'd work in practice... I just think that what ever that slimy orc number 2 was it wasn't Lurtz's mum. *shudders*