Concerning chickens being raised in the dark . . . if sunlight is replaced by dim electric lights, that is darkness. Attached are a couple of photos of chickens raised for food in dark warehouses. Also notice that the photos taken in the link provided by larryandlinda were taken in the dark, with the only light visible is from the camera flash. Also attached is a video of an egg producing facility, raided by rescuers during the bright daylight, and inside there is complete darkness. Puppy mills are also sometimes completely dark and the dogs spend their whole lives in complete blackness, so this practice seems to be commonplace. I imagine it is done to keep the animals more calm, and in the case of puppies, to keep people from looking in (they paint the windows black).
[ame]http://www.youtube.com/watch?v=haWr5WfZQ90[/ame]