It was cracked grain mash....
My feed was milled by a farmer and he was selling the farm. I stocked up as much as I could get him to make. By spring I had a couple bags the birds refused. I stored in a climate controlled basement on shelves laying on concrete floor. No mold or bugs.
They can swim for short distances. If you have young chicks that might be a problem. I have a creek and so far the only problem has been the mink coming up the creek from the forest preserve. Water attracts all predators.
The oldest is a hatchery barred Rock. Then a couple are half black jersey giant and another is half buff Orpington. Most are a mixture of the above breeds along with CX and standard dark Cornish. The extra cockerels are what I hatch for the freezer.
I wonder if any countries still use spent hens for soup or other food? Since the CX the USA has shifted to using CX for soup also.
I intended to use my old hens for soup. Other than severely injured that hasn't happened. I have hens from 2016. They have nice red combs but I haven't seen them...
Maybe the chicken feed over there has the proper nutrition for ducks too.
Here is what a big duck hatchery recommends.
https://www.metzerfarms.com/nutritional-requirements.html
Also if they are Free ranged they might be able to get the nutrition they need.