I'm no expert here, and probably shouldn't answer but here goes....I obviously don't have any advice but just a random thought: it's so interesting to me that a broody chicken will spend weeks on top of a nest... Only to kill the chicks that hatch. It seems counter productive. Why waste all that energy and nearly starve yourself keeping the eggs warm, and then kill your offspring? Does that happen with wild fowl or is it a product of domestication?
Just like with everything in nature including humans. There's no limitations to what a species is capable of doing to their offspring according to their mindset.
Some reasoning I've read that hens can be perfect sitters but once the chicks appear the hens are confused at this, viewing them as intruders or not theirs. Almost like trying to stuff day olds under a non broody hen.
In most cases these will be seen as intruders and killed. There are of course exceptions and rare cases I haven't experienced yet.
	
 Had to kill the chicks the hen hadn't managed to kill outright. Felt like killing the hen but didn't. Odd thing was the killers were great at the sitting bit. Got off the nests, ate drank and bathed every day without encouragement. Something went tilt when the chicks arrived.It's not just a chicken thing. Humans have killed their babies as have other species.
