Take the Orphaned Mammoth Calf to Khu'nok the Behemoth in the Borean Tundra.
Although you have acted valiantly in freeing the trapped calves, many of them will still die. You see, without a caretaker, these calves must fend for themselves in the wild.
But there is a way! Hope yet remains!
North of here in the mammoth fields, bordering the Scalding Pools, you will find Khu'nok the Behemoth: a mammoth as wise as he is ancient. Take this mammoth orphan and present it to Khu'nok. He will know what to do.