Some of us don't bother to finish off the cockerels before culling. I used to have a separate pen for cockerels but it's being used for a separate line of breeders now. I did several months of small, staggered hatches. Been culling the problem cockerels two or three at a time, every 10 days or so. Just separate them out the night before so I don't have to waste time trying to catch them in the morning. No special feeding plan. They taste great and the pen of youngsters is relatively calm. Works for me.