Iām putting my āhard hatā on before I answer lol
But. I often brood turkey poults and ducklings together when small until they head off to their new homes, or, if Iām bringing up some lil ones to augment our flocks....
I feed the ducklings and poults game bird starter when they are small, add some crushed brewers yeast tablets (niacin), and add a light dose of extra electrolytes / vitamins to their water (I get it from Murray McMurray hatchery...also use nutridrench from the feed store in a pinch but itās not my preference.... different balance of vitamins etc)
Once I break them up/ as they grow, I switch them to a soy and corn free crumble (I am allergic to both of those ingredients and prefer to not feed it to my laying or meat birds....).
The game bird starter is 30% protein.
The Home Grown soy/ corn free is 18% if I recall correctly.
I add a bit of rolled oats to the soy/ corn free feed for the adult ducks to cut the protein a tick more. And I never stop the niacin. Just has worked well for us. Of course they also have free access to appropriately sized grit, and then oyster shells as they get a bit older.
Sorry I know Iām not answering about the chickens- hopeful that perhaps someone else will weigh in (we donāt have chickens)
But. What I CAN say is. My ducks have always taken a very long time to feather out.
By about 20 days +/- they have the beginnings of what look like tail feathers starting to show up. Shortly after that, they start to slowly show signs of feathers growing in on their back, and wings.
Things start to happen pretty fast from there.
Ducklings in the pic are a month old for a comparison.
My heritage turkeys at a month old are pretty well feathered out and flying all over