What she said. Also, PT, you need to keep in mind that many of us are keeping our flocks with the goal to avoid the abuse that is seen in the type of flock that you are talking about. Do these flocks of up to 3000 birds have free range? Do they have deep composting litter? Not just deep...
I'd like to know who paid for that study. Smells pretty fishy to me. And without posting the study, it would be pretty difficult to assess the validity of it.