KENNETT SQUARE, Pa. -- Kentucky Derby winner Barbaro was euthanized Monday morning, just two days after the latest surgical procedure was unable to help the colt fully recover from catastrophic injuries suffered during last May's Preakness Stakes.

Surgeon: Putting Down Barbaro 'Difficult Decision' | Images

Barbaro's owners, Roy and Gretchen Jackson, made the decision along with Dr. Dean Richardson, the Chief of Surgery at the University of Pennsylvania's New Bolton Center, where Barbaro had called home for the past eight months.

"Our goal from the beginning was to do what was right for the horse," said Dr. Richardson at a news conference Monday afternoon. "This morning, after discussing all the complications that existed with the Jacksons, I really didn't think it was appropriate to continue with his treatment because the probable outcome was so poor and he would have to go through an unmanageable amount of discomfort."

Barbaro won the Kentucky Derby last May 6, then suffered a career-ending injury to his right hind leg during the early stages of the Preakness at Pimlico Race Course two weeks later.

The colt underwent a lengthy operation the day after the breakdown and the ensuing recovery process had its share of ups and downs with multiple surgical procedures. Saturday's operation was performed after an abscess developed in the right hind leg. Richardson said doctors first tried to place Barbaro's right hind foot in a cast and then a brace, but could not keep him stable or comfortable. Surgery then became necessary.

Two steel pins were placed through Barbaro's right hind cannon bone and connected to an external foot plate to alleviate weight bearing from the foot.

The procedure, which Richardson termed "risky," forced Barbaro to put too much weight on his other legs and laminitis was again developing.

"He didn't feel comfortable enough to lie down," Richardson remarked. "He wasn't comfortable standing up. The bottom line is he was just a completely different horse.

"The biggest thing that happened in the last 24 hours is that he developed fairly severe laminitis in both front legs, so that it essentially left him with not a good leg to stand on. That was just not going to work out in the long run."

Barbaro eventually lived for eight months after the initial procedure, a remarkable feat since most horses are usually put down immediately after suffering the type of injuries he incurred.

"It's a difficult day," said Roy Jackson. "We just hope a lot of the positives that have gone these eight months will continue. We hope a lot has been learned by this case that will help other horses in the future."

Before his tragic breakdown at the Preakness, Barbaro had won each of his six lifetime starts, including a thrilling 6 1/2-length victory at the Run for the Roses, and earned more than $2.3 million in prize money.