When I was a new duck mom, I made a "banned food" and a "super food" list that I added to every time I heard any info or advice on duck feeding. Now I'm a bit more experienced, and I look into each food to see just how and why it ranks the way it does. Ducks will eat almost anything so the lists are long, with many little notes, and now there's a "healthy treats" list too.
I found a neat article on line while researching the spinach dilema:
"...the oxalic acid in spinach binds with calcium and prevents our body from being able to absorb the calcium as well as it should. In egg-laying chickens and ducks, that’s the last thing you want since eggshells are comprised nearly entirely of calcium. Adequate calcium is also needed for the birds perform the contractions that push the eggs down the oviduct... by adding a splash of apple cider vinegar(acetic acid), the stomach acids are increased, which helps with absorption of not only calcium but other minerals and nutrients...I now feel comfortable adding some spinach, chard and beet greens to our ducks’ diet in moderate amounts as long as I add a splash of apple cider vinegar to their water at the same time."
https://www.fresheggsdaily.com/2014/06/the-danger-of-feeding-too-much-spinach.html
So I put spinach under "healthy treats" with a note about adding a splash of vinegar.
Also, steaming/boiling/blanching the leaves significantly reduces the oxalic acid load.
Here's a neat article about oxalic acid and waterfowl:
http://www.majesticwaterfowl.org/mmissue107.htm
I found a neat article on line while researching the spinach dilema:
"...the oxalic acid in spinach binds with calcium and prevents our body from being able to absorb the calcium as well as it should. In egg-laying chickens and ducks, that’s the last thing you want since eggshells are comprised nearly entirely of calcium. Adequate calcium is also needed for the birds perform the contractions that push the eggs down the oviduct... by adding a splash of apple cider vinegar(acetic acid), the stomach acids are increased, which helps with absorption of not only calcium but other minerals and nutrients...I now feel comfortable adding some spinach, chard and beet greens to our ducks’ diet in moderate amounts as long as I add a splash of apple cider vinegar to their water at the same time."
https://www.fresheggsdaily.com/2014/06/the-danger-of-feeding-too-much-spinach.html
So I put spinach under "healthy treats" with a note about adding a splash of vinegar.
Also, steaming/boiling/blanching the leaves significantly reduces the oxalic acid load.
Here's a neat article about oxalic acid and waterfowl:
http://www.majesticwaterfowl.org/mmissue107.htm
