This is more a question than a tip, but can you get mutton from them when they aren't tamed? Also make sure to breed them as fast or faster than you kill them. If you kill one and have some left over, cook it. It will still be very good for tames.
There is an option to kill off a tamed ovis. If you equip a weapon or tool and you open the radial options for an ovis, you get option "slaughter" which kills the ovis instantly. I stumbled apon this wyle drowning them for there meat.