Racing:Opera Mundi has been ruled out of the John Smith's Grand National.
The Paul Nicholls-trained six-year-old was withdrawn from the Aintree feature after suffering a setback.
Barry Simpson, racing manager for owner Sir Robert Ogden, said: "He's got an infection which has caused swelling in a joint.
"We walked the horse last night and he's been on the walker this morning just to see if it can be walked off — but unfortunately it can't.
"We could have left it until tomorrow morning but there's a reserve system in place and we want to play the game fairly."
Opera Mundi, the intended mount of Liam Heard, was a general 66-1 chance for Aintree glory.
"It's a setback for Saturday's race but not a big setback for the horse," added Simpson.
"We still hope to take him to the Scottish National or the Whitbread (Sandown's bet365 Gold Cup) at the end of the season."
Nigel Twiston-Davies' Ardaghey, the first reserve for the
National, has been promoted into the field and subsequently
declared a non-runner for this
afternoon's totepool Handicap Chase.
The nine-year-old will be ridden by David England, while stablemate Naunton Brook is now the mount of Andrew Tinkler.
