Hope someone can help us. For about 6 mos., my Buff Orpinton has lost her entire vent/bottom feathers. She does not feel like a water balloon. She is active, eats, lays regularly. She is 3 years old. The skin looks very red at times. We let the chickens out to dust bath 2-3x a week. About a month ago, our white easter egger started the same feather loss pattern. Now our Brahma is just starting. We have only 4 chickens, raised together. Pecking order is established, and they do not fight. Dusted the Buff with Sevin about 3 mos. ago with no change. Thanks, Ohio Chicken Mom
I had run across this link posted by another on back yard chickens a few days ago, hope it helps! http://hencam.com/henblog/2011/08/chickens-have-messy-bottoms/
It does sound like vent gleet, a fungal infection. Yogurt a little bit by mouth daily, and ACV in the water work well. Nustock can be applied to the vent area daily.