"To anyone in the same position, past, present or future, it really is the best favour you can do for an animal who is suffering. I am not an advocate of euthanasia for humans (that is a different issue)..." With you on both. One difference is that in the absence of the ability to do large amounts of abstract thought - or even read a book, watch a movie or listen to music - the point at which an animal's life becomes not worth living for them is far lower than that of a human. I know there are exceptions - Alzheimers being one horrible one - it's a tricky topic, all in all, but leaving an animal to suffer is never right.