America's Horse of the Year Wise Dan has undergone emergency surgery for a bout of colic.
The seven-year-old gelding, trained by Charles LoPresti, has won 20 of his 27 starts including two Breeders' Cup Miles.
He won his last race as recently as May when holding off the former John Gosden inmate Seek Again in the Woodford Reserve Turf Classic, but reportedly showed signs of the ailment after a routine piece of work on Friday morning.
"He had a routine gallop, trained great this morning, and about an hour after training he started acting like he was uncomfortable in the stall," LoPresti said on www.bloodhorse.com.
"We medicated him and he didn't respond. Once we got him over to Rood & Riddle (vets), they ultrasounded him and the vet saw a piece of small intestine he didn't like.
"We got him out on the lunge rein and tried to jog him around and he didn't work out of it."
LoPresti expected surgery at the Kentucky clinic to take an hour or more.