Kennett Square, Pa. ? Doctors were “pulling out all the stops” to save Kentucky Derby winner Barbaro, who suffered a significant setback in his recovery from laminitis after months of upbeat reports.

Chief surgeon Dean Richardson removed damaged tissue from Barbaro’s left hind hoof, and co-owner Gretchen Jackson said Wednesday that the colt was lightly sedated and back in a protective sling in his ICU stall at the University of Pennsylvania’s New Bolton Center.

“They’re taking extreme measures,” Jackson said. “They’re treating it very aggressively. They’re really pulling out all the stops to help him.”

Jackson said she brought Barbaro grass on Wednesday morning and said the colt’s appearance was “not as bright.” But she added her husband, Roy, visited Barbaro later in the day and his appearance had visibly improved.

Barbaro was being treated aggressively for his discomfort and is in stable condition, according to a statement released Wednesday by the Center. The tissue was removed Tuesday night.

“Things were marching along pretty smoothly until this,” Jackson said. “We’ve been there before with him. He’s a horse that wants to live.”