This is not yet proven, but the animal pathology lab at Penn State University is seeing some problems with kidney failure in ducks do to ethanol byproducts in the feed. They are listed in the ingredients as "distillery grains". Apparently, you can no longer assume that distillery grains are a byproduct of a brewery. There will need to be a lot more research to prove it, but I suggest that you not put your ducks at risk until the results are all in. The byproduct of ethanol distilling has not caused any problem with chickens. Just ducks. I took that information out of The Poultry Press, Feb issue.