Yes, you can feed coconut meat to chickens. The old dried out ones might be a little tough and dry for them though. I crack open young coconuts, drain the juice and throw it in my coop and they love the soft mushy meat, what we call spoon meat. They pick a shell clean of the spoon meat. Of coarse I have easy access to young coconuts living in hawaii where they get thrown away at the dump.
Yup, over here they get trimmed from the trees when they are small and green, they are perfect for juice and soft spoon meat. It kinda weird that I bring home snacks for the kids from the dump or off the side of the road where they are getting trimmed. I personally like the small green ones for sweeter juice and sweeter soft meat. If you have never tasted ice cold coconut spoon meat it tastes kinda like coconut jello, soft silky sweet gelatin.....mmmmmmmm