Try some animal protein. Cat food, fish, etc. Muscovy ducks need more animal protein than other ducks. They would normally get it by eating fish, frogs, bugs, etc. If they are not getting enough, then sometimes the cat food will help. That said, I am not an expert and except for some feather picking have not had this problem. Some cat food did help the feather picking. Another clue to needing more protein is if they pick up feathers that are laying on the ground and eat them.