Grand National contender A Genie In Abottle has been found dead in his stable.
The seven-year-old’s cause of death is not known, although his Irish trainer Noel Meade said the horse had shown signs of being unwell.
He was owned by Gigginstown House Stud and had been around 50-1 for the National at Aintree on 14 April.
A Genie In Abottle beat leading National hope Tiger Roll when winning at Wexford in October.
The horse was sent off 4-1 favourite for the four-mile National Hunt Chase at last year’s Cheltenham Festival, where he finished fifth.
Meade told The Guardian: “We’d been a bit worried about him but the vets couldn’t find out what was wrong with him.
“It was obviously very serious because we found him on the floor of his box.”
Gigginstown spokesman Eddie O’Leary said: “We’ve no idea what happened. He was OK in the morning and dead in his box at [Friday] lunchtime.”
Gigginstown hopes to have five runners in the big Aintree race – Tiger Roll, Alpha Des Obeaux, Thunder And Roses, Valseur Lido and Road To Riches.