Since you said it was due at 28 days, I'm assuming it's some breed of Peking duck? I know that the Khaki Campbell ducks here on the Island don't have the best livability and certainly can have birth defects, so it may be that the duckling was doomed before you helped it. That said, if the only deformity is the foot, it may manage surprisingly well in a human-managed system. We had a chick once that had a stroke and made a full recovery with a little help from us - on its own it would have starved or been eaten by the first critter that spotted it.
Wendy Smith wrote:One other thing I'm sure he had taken up the whole egg and looks like his foot isn't right. Could he have taken up the whole egg and his foot get deformed? He isn't getting up, but I have have him honey and water to see if that helps. Poor little guy.