They really shouldn't. Layer feed has added calcium in it which has a tendency to deform chicks. It is also not as high of protein that the chicks need for growth. With that said, is this a short term thing to where you can get to the feed store to buy chick starter? Or are they out with their mama in a common area? When our broodies hatch out, the chicks get what everyone else eats if they are in our common pen. We try to have pens available for each of the broodies and their clutches but sometimes that does not work. We throw out layer crumble to our birds as a treat, they normally eat layer pellet but they think they are getting a treat with the crumble. But we will also take down some chick starter and throw it out by the mama and her chicks. We haven't had any growth problems in the past three years with this method.