Kentucky Derby winner Animal Kingdom is through racing this year after being diagnosed with a slab fracture in his left hock, it was announced Wednesday by Barry Irwin, who heads the Team Valor International partnership that owns the colt.\r\nAnimal Kingdom was found to have a small fissure in the hock two weeks ago, and after being X-rayed again this week, it was determined the colt would have to undergo surgery Thursday to repair what was discovered to be a larger fracture in the same area. The surgery will be performed by Dr. Dean Richardson of Barbaro fame at the New Bolton Center in Kennett Square, Pa., just a few miles from where Animal Kingdom is based with trainer Graham Motion at the Fair Hill Training Center in northeastern Maryland.\r\nIrwin said in a media release that he is optimistic Animal Kingdom will fully recover in time to make the $10 million Dubai World Cup in late March 2012.\r\nIrwin said it is believed Animal Kingdom likely incurred the injury when finishing sixth following a troubled trip in his last race, the June 11 Belmont Stakes. Before that, the colt won the May 7 Kentucky Derby and finished second in the May 21 Preakness.\r\nThe surgery will entail a screw being inserted to compress the fracture, which will be followed by 4 to 6 weeks of rest at Team Valor&rsquo;s private barn at Fair Hill. The colt then will be sent to trainer Bruce Jackson to walk on a water treadmill, and after 90 days are up from the time of surgery, and assuming all is well, Animal Kingdom will be put into light training with Graham Motion at Fair Hill.\r\nIrwin said the tentative plan calls for Animal Kingdom to train through the fall and into the early winter at Fair Hill, after which the colt would be sent to south Florida to join Motion&rsquo;s main string of runners at the Palm Meadows training center. From there, it would be on to the Dubai World Cup, the world&rsquo;s richest race.\r\nIf Animal Kingdom makes the World Cup, he would race over Tapeta, the synthetic surface over which he regularly trains at Fair Hill.\r\n&ldquo;Graham and I have talked about this,&rdquo; said Irwin. &ldquo;No decision will be made for a while. But running Animal Kingdom in the World Cup without a prep is definitely something to consider.&rdquo;\r\nAs a 2-year-old Animal Kingdom won a maiden race at Keeneland over Polytrack. At 3, he came to prominence as a Derby prospect by winning the Vinery Spiral at Turfway Park over Polytrack.\r\nAnimal Kingdom joins a growing list of top 3-year-olds sidelined this year, along with Uncle Mo, Nehro, Dialed In, Premier Pegasus, To Honor and Serve, and others.