[nottathrowaway3]

Utility (= (pleasure minus pain) x time) is the essential good when we're talking about animal and human welfare. Good actions increase expected utility; bad actions decrease expected utility.

Machines experience no pleasure or pain and thus there is zero utility gained/lost by destroying them. Dogs and humans do; it's bad to kill or torture them.

Throwing a dog in front of a train (or killing/torturing it for research) to save a child depends on how likely it is that it will work, and how many QALYs the dog and child have left.