LaynaDon Looks like he has a deformanity, and yes like Kevin said could have been from lack or nourtients when young, how old is he and was he like this when you got him? I can see why he wouldn't be mating with your girls, but your younger one should mate your girls especially now that you have set up a pool for them. I have a drake going on 1 yr and he is a pretty busy boy.
I wonder if your drake with the problem could have crop problems? does his crop area look real distorted? can you get pic of him from the front view. and also are his legs looking normal? I have never seen this in any kind of duck but i would deff be getting back to the woman you bought them from and asking for a repalcement. As far as eating him, unless he was showing signs of illness I'd say it would be okay. Does he eat good? also if you wanted to give him sometime and see if he comes around, pick up some Poultry Nutri Drench at TSC or online and start giving oit in his water. you can even give it to them straight. I wouldn't be without it. I think an all round good vitamin like nutri drench would be better than just niacin. Let us know what you decide.

