Sacrificing any animal would be morally justifiable if it saved a human life, as is the case with kidney transplants. It does not matter that we already breed a

Sacrificing any animal would be morally justifiable if it saved a human life, as is the case with kidney transplants. It does not matter that we already breed and kill millions of pigs for meat consumption. The fact that some person with end stage renal failure could be saved, return to full health and live normally justifies the means. The species (other than human) does not matter - pigs, chimps, whatever allows is to accomplish this scientific breakthrough the fastest. Where ethics come into play is how the animal is kept during its life. And whether we prevent suffering when its time to remove the kidneys and kill the donor in the process. I would speculate that in the interest of good donor organ function, we would make sure the animal does not experience any stress.