Horse of the Year Conquistador Cielo, who won the Metropolitan Handicap (gr. I) and Belmont Stakes (gr. I) in less than a week and was syndicated for a record $36.4 million, was euthanized Dec. 17 because of founder. The 23-year-old son of Mr. Prospector stood his entire career at the Hancock family's Claiborne Farm near Paris, Ky., siring 65 stakes winners, including grade I winners and millionaires.Conquistador Cielo underwent colic surgery last December. The surgery was a success, but he injured his right knee while recuperating. He subsequently developed founder in his right front leg, and coupled with arthritis, the decision was made to euthanize him.Bred by Lewis Iandoli, Conquistador Cielo was selected 1982 Horse of the Year and champion 3-year-old male for owner Henryk de Kwiatkowski, who bought him for $150,000 at the 1980 Saratoga yearling sale. His championships primarily were due to victories in the Met Mile in record time of 1:33 and the Belmont by 14 lengths, but he also won the Dwyer (gr. II) and Jim Dandy (gr. III) Stakes in New York that summer. His Belmont win came over Kentucky Derby (gr. I) winner Gato Del Sol and Preakness (gr. I) winner Aloma's Ruler. His career ended when injured in the Travers Stakes (gr. I) during a third-place finish. He exited racing with a record of nine wins from 13 starts and earnings of $474,328 for trainer Woody Stephens.That amount was about half of what a breeding share in Conquistador Cielo cost. The value of each share was $910,000, also a record.Conquistador Cielo, who was produced from the Bold Commander mare K D Princess, sired grade I winners Marquetry, Wagon Limit, Norquestor, and Conquistarose. The last-named, from his sire's first crop of foals, raced as a de Kwiatkowski homebred. Marquetry, a millionaire on the racetrack as was another of Conquistador Cielo sons, Forty Niner Days, sired Breeders' Cup Sprint (gr. I) winners and champion sprinters Artax and Squirtle Squirt. This year, Conquistador Cielo is represented by five stakes winners and the earnings of $3 million. His career progeny earnings is $55 million.Conquistador Cielo was buried next to Unbridled at Claiborne's Marchmont Cemetery.