Is loss of feathers a symptom of a disease?

Answer 1

Loss of feathers can be caused by several things. Feather pecking is often the usual culprit. When a hen house / roost gets too crowded, the hens peck out the feathers of the chicken next to them in an attempt to get them to move over. Hens in prime condition can lose feathers from the saddle area ( at the back near the tail) from being mounted by the rooster repeatedly.

Poor quality feed can result in feather loss also. Feed with a minimum protein of 18% is required for feather production and maintenance.

Finally, chickens go into a "moult" once per year, feathers drop out and new feather start to grow. This is natural, but every chicken does this and they can look quite ugly for a few weeks until the new feathers grow in.