Neither. They run off all the food they eat when there are horny cockerels chasing pullets and each other all over the place - the pullets are running from the cockerels, and the alpha cockerels are chasing not only pullets, but chasing other cockerels to keep the subordinate cockerels away from the pullets. Once they are separated, there is no longer a reason for all the chasing to occur, so more of what they eat goes to build their body up, rather than simply to fuel their constant flight from all the chasing.