Roaring Lion: Colt recovering from emergency surgery for colic
Roaring Lion is making a "favourable recovery" after undergoing emergency surgery for colic in New Zealand.
The colt was retired for a breeding career after being named European Flat racing's horse of the year in 2018.
Symptoms of the illness were detected within 15 minutes of him being released from quarantine on Saturday.
Cambridge Stud's chief executive Henry Plumptre said: "Best-case scenario is that Roaring Lion makes a full recovery and can be returned safely to the UK."
Owned by Qatar Racing, Roaring Lion won four top-level Group One races in 2018, including the Queen Elizabeth II Stakes at Ascot in October.
The four-year-old's first covering season was spent at Tweenhills Stud in Gloucestershire before being shipped to New Zealand.
Plumptre added: "Following major surgery, we feel it is appropriate to withdraw the horse from service with all shareholders being fully refunded.
"Roaring Lion has made a favourable recovery in the first 24 hours post-surgery."
Equine colic is a life-threatening disorder of the digestive system.
Last week the 2018 Irish Oaks winner and Prix de l'Arc de Triomphe runner-up Sea Of Class, trained by William Haggas, died after a battle with the illness.
Sea Of Class, a daughter of the 2009 Derby and Arc winner Sea The Stars, was just beaten as Enable won the Arc for the second year running in October.