Each year, millions of dollars worth of thoroughbred horses bolt from the starting gate, flash by the finish line, pose for the cameras, parade past the bidders, and do their best to propagate the species at stud farms and broodmare barns. There is a lot of money riding on those horses, not just at the track, but also at the bank, where a loan secured by equine collateral is supposed to be a sure thing, not a long shot . . .