OK let's break it down. Are you feeding ducks and drakes or just ducks? If you have drakes, this has too much calcium. Drakes or ducks that aren't in lay require only about 1% calcium and too much could cause Kidney failure. Also, what age of ducks are you feeding this too? Anyways, too much protein can cause leg problems. If I were you, I would stick with a feed with about 16-17% protein. But that's just me.