Chickens cruelly beaten, stomped to death and left to die painfully and slowly. According to Mercy For Animals, that’s the “disgusting secret” behind McDonald’s Chicken McNuggets. On Wednesday, the advocacy group released disturbing hidden-camera footage capturing what it says is evidence of abusive practices at a McDonald’s chicken supplier. The investigation into T&S Farm, located in Dukedom, Tennessee, “exposed horrific cruelty to animals, including birds beaten, crammed in filthy sheds, stabbed to death with nails attached to makeshift clubs and left to suffer and slowly die without proper veterinary care,” the group wrote.