Medical Futility - Case of a Horse

I happened across this clip tonight.  It shows a veterinarian who concludes that a horse is dying and has an irreversible condition that is causing it enormous suffering.  The "surrogate" rejects the diagnosis and threatens to sue the vet.  He feels responsible for the horse's condition, for not calling the vet sooner when something might have been done.  Notwithstanding these objections, and in contrast to medicine for human beings, the vet proceeds to do what he thinks medically appropriate.