I got my first ever ducks in October - two ducklings from someone I know reasonably locally. I had a stubbornly broody hen so got her a couple ducklings to rear simply because they were available. I read up on their care and thanks to sites like this I have done pretty well, I have reared two gorgeous, healthy drakes. So I contacted the breeder as she had promised if it turned out I had 2 drakes she would swap one for a duck as she has nothing but ducks and was a mixed chatching of three breeds (Rouen, Magpie and Aylesbury) I chose to send Noodle (the Magpie) back and keep Dumpling as I want to rear for the table, and the breeder asked if I could take on (as well as the swapped girl) one with a broken leg that needs one on one care... I said I would as I've trained in animal care.... Well it's shocking! both girls development is incredibly stunted and as far as I can tell it's all down to one thing... they have had no brewers yeast or any other form or supplemental niacin. The difference between them and Dumpling or Noodle is immense, they have rickets, even the 'healthy' one has a limp and bendy legs. The one inside has a badly twisted leg and is pretty weak but even 24 hours later is improving immensely, she is eating like the clappers and drinking well and moving well in water to take weight off leg. (was broken 3 weeks ago and partially healed twisted) Dumpling with Becca - they hatched the same day! Jemima (Mima) was also hatched on the same day... yet looks 5-6 weeks younger with her scrubby down... all three are 14 weeks I am now supplementing with brewers yeast, upped their protein and calcium and vitamin C. Mima is staying in the house and having daily short sessions of swimming and blow dries (5 min swimming) to allow her to get some exercise without straining the leg. Her left leg is twisted in and she'll probably always have a pretty severe limp but she's chatty and bright and eating/drinking/grooming and generally ducky so I think fairly comfy with her new splint on. but I think this is clear enough evidence that nutrition has a profound effect not just on health but overall development.