Good thought on the chicken feed - maybe some of the movable horse panels surrounding the chickens' house could do the trick - plus that would take care of worrying about the horse doing damage to/getting hurt on the chickens' house.
I love my chickens, but we only have four right now - Buff Orpington, Americana, Road Island Red, and New Hampshire Red.
Once we close on our new place I want to get four more for starters - a White Leghorn and Barred Rock for certain if I can get them, and I'll let the kiddos choose the other two.
My first two chickens ever were a Barred Rock and a White Leghorn. They were the best layers

. Leghorns are usually spazzes, but we handled Trigger so much as a chick that she was extra friendly, and
always ready for a handout

.