We have just a couple of egg-layer chickens left that have been malting and not laying for a while. Their production rate had dropped off anyway and we figured that they were coming to the end of their useful productive life.
My SO was in the pen replenshing their feed when the new dog bashed through the closed but unlocked door, raced to the nearest chicken, and in one bite had killed it. He would not drop it straight-away, took me to go over and tell him to drop it. Came out of the pen when told and did not go for the other bird. Shame in a way as it could have been handy to have disposed of both at the same time. Seemed so quick that it must qualify as humane.