Duck feed, supplement with grains or...

I recently got a couple of ducks to work on the slug problem. They're eating the aforementioned slugs, dropped fruit (cherry, apple, pear),  squash, tomatoes, watermelond rind and grass and kitchen scraps. I've noticed they really like the stale rolled oats I gave them so I'm thinking about feeding them some oats occasionally.
I'm growing sunflowers for their winter feed alongside apples and winter squash that I'll store but I get a feeling it won't provide them complete nutrition for egg laying.

Should I supplement their feed with some grains and which grain would be the best choice? Most of the poultry feed in my country is medicated or the origin of ingredients is iffy.

Winter feed for ducks is a good question.  I've had chickens for many years, but haven't done a lot with ducks -- I've been considering switching to ducks because of the much higher nutritional value of their eggs.  But, am wondering if, during a frozen, snowy winter, it might be easier to feed a few chickens adequately than to feed the ducks and keep them healthy and laying?

Kathleen

Medicated feed is said to kill waterfowl. The missing element in your winter ration is protein. I would add perhaps 50/50 soaked barley and soaked pigeon peas or some other legume. How many ducks do you have? Perhaps you could feed them maggots, meal worms, earth worms or even frozen or dried duck weed or algae.

It's just 4 ducks... I think soaking some grains/legumes and some duckweed (ifi I manage to collect enough) will be the best solution