By Karolin Schaps

LONDON (Reuters) - The world’s biggest dog show was thrust into a murder mystery fit for an Agatha Christie novel when a champion Irish setter died after its owner said it had been fed steak laced with poison.

The death of three-year-old Jagger rocked Britain's Crufts show, held annually since the reign of Queen Victoria, and unnerved a dog-showing world that some fear may have just become too competitive.

Dee Milligan-Bott, co-owner of Jagger, whose pedigree name was Thendara Satisfaction, said an autopsy had concluded he had eaten steak laced with several types of poison that led to a painful death for the dog on his return to Belgium.

She called on fellow breeders to track down the poisoner.

"I ask you all to unite in finding the perpetrator who did this," Milligan-Bott, an experienced Irish setter and Afghan Hound kennel owner who has officiated at Crufts, told reporters at her home in central England.

Although she said the autopsy showed the poisoning must have taken place at Crufts, she refused to point the blame at rivals.

"I certainly don't want our dog shows, the places we work so hard to get to, (to) become a ground of finger-pointing and suspicion," Milligan-Bott said.

"I therefore need you all to know that we can't, and we won't think this was an act of another exhibitor. If we thought this we couldn't go."

Jagger died at his co-owner's home in Belgium, and some British newspapers have speculated that he might have been a victim of mistaken identity as his half-brother Pot Noodle is another successful show dog.

Owners flock to a cavernous conference center outside Birmingham for Crufts, entering their pedigree dogs against 21,500 others in a series of competitions that culminate in Best in Show.

A Scottish terrier from Russia won that title on Sunday, two days after Jagger's death.

The show was founded by Charles Cruft, who worked for a dog biscuit manufacturer. Winners, which emerge from categories such as toy dogs, gun dogs, hounds and terriers, often have striking names. A poodle called Afterglow Maverick Sabre, also known as Ricky, won Best in Show last year.

The Kennel Club, which organizes Crufts, issued a statement of condolence.

"The Kennel Club is deeply shocked and saddened to hear that Jagger the Irish Setter died some 26 hours after leaving Crufts," Kennel Club Secretary Caroline Kisko said.

"We have spoken to his owners and our heartfelt sympathies go out to them. We understand that the toxicology report is due next week and until that time we cannot know the cause of this tragic incident," Kisko said.

A Kennel Club spokeswoman said it was unclear where the alleged incident happened and that until the toxicology report was received it was difficult to speculate.

In any case, the tabloid Sun reported, "police are following all leads".

(Writing by Guy Faulconbridge and Michael Holden; Editing by Giles Elgood)