"The cat wasn't trying to protect him," said Jonathan Kraft, who runs the Arizona-based nonprofit group Keepers of the Wild. "That was a typical killing bite."
"I admire the guys, I just think they are sending a wrong message," Kraft said. "The message needs to be: These are wild animals."
Horn's partner, Siegfried Fischbacher, said Wednesday in interviews on CBS News Early Show and elsewhere that the animal had been trying to help Horn after the illusionist slipped during Friday's performance.
"'Don't harm the cat.' That was [Roy's] last words. And so that tells me he knew exactly the cat didn't want to harm [him]," Fischbacher told Early Show co-anchor Harry Smith.
Fischbacher said he was backstage when the Royal White tiger named Montecore took hold of Horn's neck and dragged him offstage. Show workers set off fire extinguishers to distract the tiger, which then scurried to his cage.
Louis Dorfman, a Dallas animal behaviorist, said Fischbacher's account of an accidental mauling was "a beautiful story but it just doesn't wash."
"Stress led to the bite," said Dorfman, who works with the International Exotic Feline Sanctuary in Texas. "It was an outlet for his irritation. Roy got lucky."
"Siegfried & Roy" debuted in 1990 at The Mirage and earned the hotel-casino about $44 million in annual revenue. The show's 267 employees have been told to find new jobs.
Those who have seen a surveillance tape of the performance agree with Fischbacher, reports CBS News Correspondent Lee Cowan.
"The cat did not attack him, the cat picked him up," said casino developer Steve Wynn. "There was not a speck of violence in any of this. There was no shaking, there was no biting, there was no use of full strength. Roy's neck would have been snapped like a twig."
The show's production manager agrees.
"It absolutely did not have a vicious appearance to it," Bob Salyer told CBS News. "He didn't, like, grab him and shake him, it was nothing like that all. So I could see what people thought this was part of the show, 'Wow, how does he get out of the cat's mouth?' you know?"
Horn, 59, was injured before a sellout performance of 1,500.
He remains in critical condition and cannot speak. Fischbacher confirmed to The Associated Press that Horn suffered a stroke after the attack but is now communicating through hand signals.
MGM Mirage spokesman Alan Feldman cautioned that the full story probably won't be known until Horn can talk.
Fischbacher hinted at a return to the stage if Horn recovers, saying the duo would "take a different path, I'm sure, but ... the show is our life."
The duo's manager, Bernie Yuman, told The Associated Press early Thursday that Siegfried would never continue to perform without his longtime partner. "It is 'Siegfried and Roy' and that's the way it began and that's the way it will always be," he said.
The cat remains quarantined at the casino.
Surprise inspections by the U.S. Department of Agriculture showed nothing out of the ordinary — "a clean slate," said one investigator — year after year, reports Cowan.