"The culling of puppies in such huge numbers is evidence alone that greyhounds are not born performers or chasers, they are simply trained to perform and chase, those who don’t, are dispatched without a second thought." source Greyt Exploitations
Dog racing is not a sport. The dogs are horribly treated, killed in the most inhumane manner you can imagine when they don't "perform" on the track and live miserable lives as track dogs. Rescue one, if you can.