The 139th Kentucky Derby takes place at Churchill Downs on Saturday. The spectacle is as much a soiree and fashion occasion as it is a prestigious horse race. Thousands will flock to the grounds in their Sunday best. For women, flowered floppy hats and sundresses are always a hit. As for the men, a seersucker suit with a festive tie will do. But all that beauty and enimence won't hide the fact that horse racing can be, and often is, a dark sport. To that effect, PETA is launching a new mobile billboard, which will be driven outside the racetrack, to remind visitors of the cruelties that can lie beneath the surface of the thoroughbred sport. The ad, created by a Temple University student, shows a horse with a marking on his nose that looks like a syringe. (He probably races under the name Old Needleface.) The copy reads, "Drugs. Breakdowns. Death. Horse racing is a bad bet." PETA had better get the ad out there early tomorrow, though, because we all know no one remembers anything after that second mint julep.