I find all this quite interesting. I try to keep my unnatural chicken rearing (if a broody isn't raising the chicks, it's unnatural) as natural as possible.
My chicks went into the built in brooder in the coop the day they arrived from the hatchery. They are under a brooder plate with a towel draped over it and touching the floor on three sides. I left lights on in the brooder room for just 2 days to make sure the chicks had recovered from shipping stress.
I went out to the coop on the morning of their 5th day of life after the lights had been off overnight for the first time for them and it was 28F. Where were the chicks and what were they doing?
Zipping and running all over the brooder having a grand time and stuffing their little crops silly. They are feathering out beautifully and flying all over the place now.
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I'm certainly not advocating not to watch these little ones closely for issues as you have to act quickly if something goes sideways. But they are so much hardier than we give them credit for.
Incidentally, I've only had one chick out of 15 get pasty butt, one time. That's it.