I would take it out, but not sure I would put it with the three day chicks..unless you can watch it for a while. They tend to get knocked over by the older ones, and can actually squish the little one. Is there some way you can separate them in the same brooder while they can still see each other until the little one is dry and up and waling about, in about a day?
Had to pull it outta there. Put it with the varsity squad in the brooder but they started pecking it. Ganged up in the poor little thing actually. Put it in another box sharing the same heat lamp till it gets it's game legs.