KENNETT SQUARE, Pa. — Barbaro still looks every bit the champion, and that's why his deteriorating condition is heartbreaking: The Kentucky Derby winner has a hoof disease so serious his veterinarian says the colt is "a long shot" to survive.

It's not how Barbaro looks, though, but how he acts that will determine how much longer he lives.

Dr. Dean Richardson said Thursday that Barbaro has a severe case of laminitis in his left hind leg, a painful, often fatal disease caused by uneven weight distribution in the limbs.

"If he starts acting like he doesn't want to stand on the leg, that's it — that will be when we call it quits," a blunt Richardson said Thursday during a news conference at the University of Pennsylvania's New Bolton Center.

"It could happen within 24 hours," he added.

The vet, who has been treating Barbaro since the colt suffered catastrophic injuries to his right hind leg in the Preakness on May 20, said 80 percent of the Derby winner's left hoof wall was removed Wednesday with the onset of the disease.

Though he looks just fine — "his ears are up, he's bright, he's looking around" — that doesn't reflect the true nature of his condition, termed "poor" by Richardson.

"I'd be lying if I said anything other than poor," he said. "As long as the horse is not suffering, we are going to continue to try to save him. If we can keep him comfortable, we think it's worth the effort."