wow, that's kind of a mind boggling number! you are talking industrial numbers, for which the care and management are super critical. if you can't give them the proper space, I would start finding folks to take some/most off your hands. there are so many problems that will crop up, it's hard to know where to begin. without the proper space for them to roam, they will start pecking on each other, you will see full on cannibalism. to get around this, the industry clips their beaks, but not fun to resort to and it can be avoided be proper space. the river of poop you will be dealing with is going to require serious management, like tractors, industrial scale composting. if you don't deal with the droppings properly, you will have a disaster on your hands. venting the ammonia is tricky, if you added forced air, the draft can cause problems for the birds, and if you don't have enough venting, the ammonia can kill. the ammonia is just one of the many issues. the microbes can go nuts. if the birds are too close together, they get stressed, and one of those stresses is added microbial load, they get sick from wallowing in such a nutrient dense muck. as one gets sick, it quickly passes disease to the next, in close quarters, particularly through the water. you would need a substantial watering system, usually a nipple system, continuous on demand, pressurized. with such large numbers in a small sapce it becomes difficult to avoid the use of medications/medicated feed. honestly, I'd gradually move up to these kind of numbers. this is by no means a backyard chicken scenario.
