I wouldn't feed it as the only feed. My Ducks ate some wheat today and they loved it, but they also get other feed. They also eat the chicken scratch and they free range so they will eat about anything.
I've been told wheat is fine as a part of the feed. A caution is that if it is not dried properly, it can get moldy, and moldy feed is bad news.
I have added a small handful of dry hard winter wheat to my ducks' feed pellets from time to time. I have also given them sprouted wheat, and wheat greens (just let the sprouted wheat grow a few inches and green up). Wheat has some nice protein in it. It's a grass. Another caution is not to give them too much "seedy" feed. I forget what problem that could cause. Nettie or Duck_feeder may be able to enlighten us on that.
So, I would consider getting some to add to their feed occasionally, but would keep it in a dry, tight container somewhere cool.
By the way, I also add rolled oats to their feed. I started doing so to cut protein percentage, but have kept it up to give them something a little different, with some nice fiber in it.
If you're interested in feeding your duck grains, I recommend getting a copy of Storey's guide to raising ducks. In appendix A there are examples of mixes of grains you can feed your duck to ensure a healthy diet.
I prefer using pellets as their primary feed because they can't ignore something in their feed that has an essential nutrient.
Thanks for replying! I'm reading the Story's giude to raising Ducks right now. Great book! I might just feed them layer pellets or something similar. I thought about feeding them scratch grain more but I don't want them becoming fat on the cracked corn.