Calf Manna okay for ducks?

[chicken_boy_Kurt]

I feed my rabbits a small handful of Calf Manna every day. I was reading the bag and it said recommended feeding for chickens. But I don't have chickens. Is it okay to feed to my ducks? Would it be helpful to feed to my ducks? I raise Saxonies for eggs and show and Pekins for meat. They're together and right now I feed Purina Flock Raiser.