The 12-year-old, who carried the colours of Ray and Anita Green to glory at Ayr in 2010 and 2012 has failed to show any of his zest this season.
A course specialist at Scotland’s premier venue, he gained five of his seven wins there. Trainer Andrew Parker said: “Though he looks well enough, the old sparkle isn’t there anymore even though this is normally his time of year. It was same in the gallop we did at Musselburgh (on Sunday) and the decision to call it a day was taken after a discussion with myself and Mr Green on Monday morning.
“Merigo certainly doesn’t owe us anything and Mr Green always looks after his old horses when they retire. For a small trainer like me he was a horse of a lifetime and I’ve loved every minute of looking after him.”
The Greens could still be represented in the SGN as Rival D’Estruval, still going well when falling two out in the National Hunt Chase, is expected to be given an entry.