The ones I used needed it to be at least 55F to begin working. They never felt as warm as a mama hen does though, but once the chicks were ambulatory, they seemed to do okay as long as they didn't get chilled from being wet or getting out and losy
I used to. I didn't really like them though. I couldn't use them with shipped chicks, I couldn't use them outside in the shed, it was a lot more work changing the height constantly as they grew and they loved to poop on it.
I much preferred just using a heat lamp since I generally had to add...
So far I haven't had anything truly destroying. Just the dog I mentioned yesterday on my thread, and the mystery predator that comes and goes. But nothing like what a coon can do over night yet
Yes, just two girls though. One had a foot issue that ended up in her toes having to be broken for her to walk easily, but both were pretty and healthy otherwise
I'm also doing similar things. Ducks are my new focus thanks to the mareks. I have a large handful of chickens staying, but they won't be reproducing much at all, they're just ones I can't bear to cull unless they start showing symptoms.