hens neck feathers are completely gone

[foghorn86]

If one of my hens neck feather are completely gone on the back of her neck, will they grow back next year?

 

[dawg53]

If she's in molt, they will eventually grow back. You can feed them gamebird feed which is higher in protein to help with feather regrowth.
I forgot to add that you should visually inspect her for lice/mites as well.