Greyhounds are bred to race. When they can no longer run fast they have reached the end of their useful existence. It is possible to keep them as pets, but the morality of such a decision is at least questionable. Retired they consume protein that could be more compassionately used to relieve famine in the developing world. It is a source of outrage to the citizens of poor nations: should canine appetites really take precedence over the survival of human children?