skeeeter
Crowing
I too, would consider gamebird feed or dried catfood as first choices over people food, even.I agree with meat and dairy. Especially if it's just a single hen. It's not just about protien. Its also about what protien is hugher in the aminos required.
Tins of sardines, dairy, silverskin/gristle trimmings.... little bit of fat from your own meat. Left over roast bones to peck at are also entertaining for them. They really don't need much. It's easy to overdo it.
Alternatively gamebird feed for birds like Guinea fowl and quail is often higher in protein.