French import Manduro's Son has been euthanised due to complications from colic.
The five-year-old developed colic after undergoing successful surgery on a pastern injury suffered in trackwork at the Werribee quarantine centre.
A three-time winner up to 2500m in France, Manduro's Son was being prepared by Mike Moroney for his new owners.
Racing Victoria's head of equine welfare, Dr Brian Stewart, said Manduro's Son was being operated on for the colic when he suffered complications and the decision to euthanise him was made in the horse's best interests.
Stewart said he was under anaesthetic at the time and suffered no pain.