Found this video about how raising chickens fits into agriculture as a whole. The farmer's explanation of how chickens fit into cycling animals through his pasture, the feed load of the chickens, and the timing of the flocks is quite informative. Even though he does this on a large scale, manually, he discusses how well this method scales up or down. He talks about how it is done with 2000 square feet of land. Not much larger than the footprint of many houses. He talks about how the tractors and rotation tend to stop the spread of pathogens. He is apparently an ardent supporter of organic farming and organic food, but is not strident about it. His explanation is so matter-of-fact that it is overwhelming. I felt that there was a lot of information in the film. It was well worth the half-hour it ran. Chris Titled "Chickens at Polyface Farm".