Sadly very time a fancy race horse breaks a leg, they very quickly get sent off to the knackery to be made into Meaty Bites or Pal. Given these horses can be worth millions of dollars it seems a terrible waste.
The obvious solution is racing prosthetics. After all, it worked for Oscar Prestorious. He was really quick and everyone loved him (until the unfortunate shooting his girlfriend thing). I think people would get behind a blade runner horse.
Do you think racehorses say "break a leg" to each other before they race? That would be some cold shit... I guess they probably wouldn't say that unless they had Mr Ed abilities.