Half of my laying hens are sick. Not sure what it is or how to cure it if possible. I had 25 healthy hens then a lady gave me 7 more. I kept them separate for a couple weeks, as soon as I put them together I noticed a couple of them coughing and chirping then nasal and eye discharge. They started getting lethargic and losing weight. As soon as I saw the first symptoms I started separating them, but too late. Now over half of my other hens are slowly doing it also. Plus egg production has gone down. I have treated them over the last 10 weeks with no luck. I have even switched to 3 different antibiotics and higher protein food and nothing helps. I have also had a few get just 1 eye infected with a thick ,hard puss. I was able to clear the eye infections at the cost of the eye. All the treatments seem to prolong the life span, some even seemed to start getting better. But as soon as I stopped treatment after a few weeks all symptoms started coming back within a few days. The product "Vet RX" seems to make the the breathing better, but it's not a cure. I have 50 ISA pullets that are not exposed and 70 one month old chicks.
Now, I need to know a few things. First, should I go ahead and cull all sick and exposed chickens? Can anyone tell me what this might be? What vaccines should I get for all the young chickens and where can I get them? What should I use to sanitize the sick chicken house and yard? And finally, how long do I wait to dare put any healthy chickens in that house?
Sorry so long, but after all my research and trials I am at a loss!