If you make it so that characters spawn corpses when killed, then you can simply apply a "butcher" skill to the corpse. The skill could also be used as a means of acquiring food.
Hidden skill is cool but a little bit clumsy. You can't do the harvesting barehanded anyway. Maybe a hidden tool that uses existing skills like medicine and science would be better. An illegal tool that is available only from specific organizations.
"Demeter 3000! Harvesting made easy!! Sign up for the Harvester club and get one free today! *joining fee may apply"