This is an idea, and I'd appreciate others' thoughts.
Since the baby is a duckling, and (most, to my knowledge) ducks and ducklings enjoy fish, how about some sardines? My hesitation would be the amount of salt - I am simply not sure. If you could find sardines in water, not salted or oiled, that would be a source of Vitamin D, calcium, and phosphorus, all of which are good for bones.
Similarly, feeder fish would likely contain those nutrients as well, I would think, and salt would not be a concern. Some are concerned about bacteria in feeder fish, though.
Then there are, according to wormdigest, earthworms as a source of Vitamin D.
So there are duck-yummy foods that contain D.
By the way - Vitamin D is added to cow's milk - it does not naturally contain it. (Every now and then I run into someone who thinks it comes out of the cow with D.)
Since the baby is a duckling, and (most, to my knowledge) ducks and ducklings enjoy fish, how about some sardines? My hesitation would be the amount of salt - I am simply not sure. If you could find sardines in water, not salted or oiled, that would be a source of Vitamin D, calcium, and phosphorus, all of which are good for bones.
Similarly, feeder fish would likely contain those nutrients as well, I would think, and salt would not be a concern. Some are concerned about bacteria in feeder fish, though.
Then there are, according to wormdigest, earthworms as a source of Vitamin D.
So there are duck-yummy foods that contain D.
By the way - Vitamin D is added to cow's milk - it does not naturally contain it. (Every now and then I run into someone who thinks it comes out of the cow with D.)