My mom has several pens with different kinds of chickens in each one. The pen is basically a big one with wire running through the middle to separate them into smaller pens. Recently the chickens in the middle pen has began dieing.
It's odd. It starts out with the tail feathers dissappearing. (Even the rooster has none) then the feathers from around there butt disappear too. I noticed today that the chickens in this one pen seem to have very skinny legs. (Of course I'm comparing them to my very fat chickens so maybe they just look skinny lol). Anyway, they seem to simply die at night. She seems to be losing 1-3 chickens a night to whatever this is. I'm thinking it must be some kind of parasite since they are all feed the same thing and only one pen seems to be effected by it. I gave her some DE to put in the feed. But does anyone have any idea what could be causing this or how to stop it? I made a picture of one of them after it had died. I'm not sure how to explain it but it honestly looks like it's butt is maybe stretched. ( I would post the pic but didn't want to gross anyone out). I believe they also have diarrhea. If anyone has any ideas on what this could be or what to do about it I would really appreciate it.

Maybe give your local University Extension office a call.

Or your feed store - they often have good common sense answers. In the meanwhile, I'd move all the chicks from the affected pen, clean it all out, and wash it down with a weak bleach/water solution to try to eradicate any parasites or disease that might be causing the problem. I wouldn't put those chicks in with any others so they don't spread whatever it is they have. Sad.

If they are separated only by wire, then if what they have is contagious it would easily spread from one pen to another. Chickens often will pick off and eat the feathers of others in the flock. It's usually a sign that they need more to pick on or scratch through. Once they taste blood they will pick at the rear ends of each other and they will bleed to death quickly. I'd recommend making sure they have lots of things to pick and scratch on. Like sod, Alfalfa hay, or you can buy a block of compressed mixed seeds that they can pick on. A combination of a couple of those options would be good. Chickens that are locked in all the time are more prone to doing this. If the dead chicken has a red and swollen vent in the back, it's a good sign that is what's happening. A picture of the back end of a dead one would be helpful, I know it would be gross to look at, but I could easily tell by seeing it.