KENNETT SQUARE, Pa. (AP) -- Kentucky Derby winner Barbaro was euthanized Monday after complications from his gruesome breakdown at last year's Preakness, ending an eight-month ordeal that prompted an outpouring of support across the country.

"We just reached a point where it was going to be difficult for him to go on without pain," co-owner Roy Jackson said. "It was the right decision, it was the right thing to do. We said all along if there was a situation where it would become more difficult for him then it would be time."

A series of ailments, including laminitis in the left rear hoof and a recent abscess in the right rear hoof, proved too much for the gallant colt.

Barbaro battled in his ICU stall for eight months. The 4-year-old colt underwent several procedures and was fitted with fiberglass casts. He spent time in a sling to ease pressure on his legs, had pins inserted and was fitted at the end with an external brace. These were all extraordinary measures for a horse with such injuries.

Roy and Gretchen Jackson were with Barbaro on Monday morning, with the owners making the decision in consultation with chief surgeon Dr. Dean Richardson.

"I would say thank you for everything, and all your thoughts and prayers over the last eight months or so," Jackson said to Barbaro's fans.

The news that Barbaro had been euthanized first was reported on the Thoroughbred Times Web site.

On May 20, Barbaro was rushed to the New Bolton Center, about 30 miles from Philadelphia in Kennett Square, hours after shattering his right hind leg just a few strides into the Preakness Stakes. The bay colt underwent a five-hour operation that fused two joints, recovering from an injury most horses never survive. But Barbaro never regained his natural gait.

"We loved him. He was great," said Peter Brette, Barbaro's exercise rider and assistant trainer for Michael Matz. "He did everything we ever asked of him. He could have been one of the best. What a fighter he was."

Barbaro suffered a significant setback over the weekend, and surgery was required to insert two steel pins in a bone -- one of three shattered in the Preakness but now healthy -- to eliminate all weight bearing on the ailing right rear foot.

The procedure Saturday was a risky one, because it transferred more weight to the leg while the foot rests on the ground bearing no weight.

The leg was on the mend until the abscess began causing discomfort last week. Until then, the major concern was Barbaro's left rear leg, which developed laminitis in July, and 80 percent of the hoof was removed.

Richardson said Monday morning that Barbaro did not have a good night.

"This horse was a hero," said David Switzer, executive director of the Kentucky Thoroughbred Association. "His owners went above and beyond the call of duty to save this horse. It's an unfortunate situation, but I think they did the right thing in putting him down."

Brilliant on the race track, Barbaro always will be remembered for his brave fight for survival.

The story of the beloved 4-year-old bay colt's fight for life captured the fancy of millions. When Barbaro broke down, his right hind leg flared out awkwardly as jockey Edgar Prado jumped off and tried to steady the ailing horse. Race fans at Pimlico wept. Within 24 hours the entire nation seemed to be caught up in a "Barbaro watch," waiting for any news.

Well-wishers young and old showed up at the New Bolton Center with cards, flowers, gifts, goodies and even religious medals for the champ, and thousands of e-mails poured into the hospital's Web site just for him.

"I just can't explain why everyone is so caught up in this horse," Roy Jackson, who owned the colt with his wife, Gretchen, has said time and again. "Everything is so negative now in the world, people love animals and I think they just happen to latch onto him."

Devoted fans even wrote Christmas carols for him, sent a wreath made of baby organic carrots and gave him a Christmas stocking. The biggest gift has been the $1.2 million raised since early June for the Barbaro Fund. The money is put toward needed equipment such as an operating room table, and a raft and sling for the same pool recovery Barbaro used after his surgeries.

The Jacksons spent tens of thousands of dollars hoping the best horse they ever owned would recover and be able to live a comfortable life on the farm -- whether he was able to breed or not. The couple, who own about 70 racehorses, broodmares and yearlings, and operate the 190-acre Lael Farm, have been in the horse business for 30 years, and never had a horse like Barbaro.

As the days passed, it seemed Barbaro would get his happy ending. As late as December, with the broken bones in his right hind leg nearly healed and his laminitis under control, Barbaro was looking good and relishing daily walks outside his intensive care unit.

But after months of upbeat progress reports, including talk that he might be headed home soon, news came Jan. 10 of a serious setback because of the laminitis. Richardson had to remove damaged tissue from Barbaro's left hind hoof, and the colt was placed back in a protective sling. On Jan. 13, another section of his left rear hoof was removed. After Barbaro developed a deep abscess in his right hind foot, surgery was performed Saturday to insert two steel pins in a bone.

This after Richardson warned last December that Barbaro's right hind leg was getting stronger and that the left hind foot was a "more formidable long-term challenge."

Even before the injury that ended his career, Barbaro had earned his fame for simply being a magnificent racehorse. Foaled and raised at Sanborn Chase at Springmint Farm near Nicholasville, Ky., Barbaro always stood out in the crowd. "He was an enormous foal," recalled breeder Bill Sanborn. "He was a tall and leggy horse, and when he grew it was like in two-inch spurts."

When the Jacksons sent Barbaro to trainer Matz over a year ago, exercise rider Brette climbed aboard and said "I thought he was a 3-year-old."

A son of Dynaformer, out of the dam Le Ville Rouge, Barbaro started his career on the turf, but Matz knew he would have to try his versatile colt on the dirt. He reasoned that if he had a talented 3-year-old in America, he'd have to find out early if his horse was good enough for the Triple Crown races.

Barbaro was good enough, all right. He won his first three races on turf with authority, including the Laurel Futurity by eight lengths and the Tropical Park Derby by 33/4 lengths. That's when Matz drew up an unconventional plan for a dirt campaign that spaced out Barbaro's race to keep him fit for the entire Triple Crown, a grueling ordeal of three races in five weeks at varying distances over different tracks.

Barbaro won the Holy Bull Stakes at Gulfstream Park on Feb. 4, but his dirt debut was inconclusive since it came over a sloppy track. After an eight-week break, an unusually long time between races, Barbaro came back and won the Florida Derby by a half-length over Sharp Humor despite an outside No. 10 post.

The deal was sealed -- on to the Derby, but not without criticism that Barbaro couldn't win coming off a five-week layoff. After all, it had been 50 years since Needles won the Derby off a similar break. But Matz was unfazed, and stuck to his plan, saying all the time he was doing what was best for the horse.

Not only did Barbaro win the Derby, he demolished what was supposed to be one of the toughest fields in years. The 61/2-length winning margin was the largest since 1946, when Assault won by eight lengths and went on to sweep the Triple Crown.

The 55-year-old Matz, meanwhile, was living a charmed life. Before turning to thoroughbreds eight years ago, he was an international show jumping star, and a three-time Olympian and silver medal winner who carried the U.S. flag at the closing ceremony at the 1996 Atlanta Games. He also survived a plane crash in Iowa in 1989 and became a hero by saving three children from the burning wreckage. The crash killed 112 of the 296 people on board United Flight 232.

In Barbaro, Matz truly believed he was training a Triple Crown winner. He often said Barbaro was good enough to be ranked among the greats and join Seattle Slew as the only unbeaten Triple Crown champions.

But two weeks later after the Derby Barbaro took a horrible misstep and one of the most extraordinary attempts to save a thoroughbred was under way. The injury was considered to be so disastrous that many thought the horse would be euthanized while still at Pimlico Race Track. Instead, Barbaro was transported that night to the New Bolton Center's George D. Widener Hospital for Large Animals and was operated on the next day by Richardson.

The injuries were as serious as everyone feared: Barbaro sustained a broken cannon bone above the ankle, a broken sesamoid bone behind the ankle and a broken long pastern bone below the ankle. The fetlock joint -- the ankle -- was dislocated. Richardson said the pastern bone was shattered in "20-plus pieces."

Barbaro, who earned $2,302,200 with his six wins in seven starts, endured the complicated five-hour surgery in which Richardson inserted a titanium plate and 27 screws into the broken bones. After calmly awakening from anesthesia, he "practically jogged back to his stall" looking for something to eat.

At the time, Richardson stressed Barbaro still had many hurdles to clear, and called chances for a full recovery a "coin toss." Afterward, though, things went relatively smoothly. Each day brought more optimism: Barbaro was eyeing the mares, nickering, gobbling up his feed and trying to walk out of his stall. There was great hope Barbaro somehow would overcome the odds and live a life of leisure on the farm.

But by mid-July, Richardson's greatest fear became reality -- laminitis struck Barbaro's left hind leg and 80 percent of the hoof was removed. Richardson recalled recently what it was like when he met with the Jacksons, and Matz, and his wife, D.D., to deliver the news.

"It was terrible," Richardson said. "I wouldn't have blamed anyone at that point for saying they just couldn't face the prospects of going on."

But Barbaro responded well to treatment, and his recovery was progressing until a final, fatal turn.