i've read numerous studies regarding high protein and angel wing in ducks. not one of them involved a feed less than 24% protein, usyally closer to 30% like a gamebird feed. Even then, its of greatest concern to hatchlings as they grow. The flock raiser is fine, needs no adjustment. Anecdotally, i've raised numerous ducks on 24% for the first few weeks, then dropped to 20% for the rest of their lives w/o incident.