ARCADIA, Calif. — Through the 14 races run and nationally televised over the weekend as part of the Breeders’ Cup World Championships here at Santa Anita Park, anyone who loved this picturesque racetrack — or the beauty of thoroughbreds in full flight — held their breaths as one multimillion-dollar race after another concluded without a horse taking a bad step.

After all, 36 horses had died here since Dec. 30 in all kinds of ways.

So, when the New York-based horse Vino Rosso crossed the finish line here on Saturday to win the $6 million Breeders’ Cup Classic, the event’s marquee race and the final one on the card, the collective exhale of relief was nearly audible.

Unnoticed by most of the announced crowd of 67,811, however, was that a horse named Mongolian Groom had taken that dreaded bad step and was suddenly pulled up in the stretch by his jockey, Abel Cedillo, after establishing himself in third place and looking every bit like a contender to win North America’s most prestigious race.

Instead, an equine ambulance was soon barreling down the stretch and, as NBC broadcast to its prime-time audience a jubilant celebration in the box of Vino Rosso’s owner, Mike Repole, Mongolian Groom was loaded into the truck and taken to a hospital on Santa Anita’s barn area beneath the rouge-tipped San Gabriel Mountains.