Bovine warts are caused by a papilloma virus. The virus is trying it’s best to hide from the animal’s immune system. They have no sensation as they are really just layers and layers of tissue trying to disguise itself, not dissimilar to some forms of cancer. By traumatizing them we can stimulate the immune system to recognize them and mount an immune response. By twisting them off we both invite trauma and mitigate the risk of hemorrhage. Win win!