I have a broiler with a chest full of air. It really does seem to be just air, not fluid, but I've never seen anything like it before. It's only one bird out of the batch (they are 6wks old but we noticed it about 5 days ago when we were moving the tractor). Anyone seen something like that before and what could it be? We are planning to cull the bird this afternoon if I can't find out anything about it and determine that it won't affect the meat. It doesn't seem to be a very big bird under that puffed up chest.