A steer has been put down after sustaining a severe neck injury in a rodeo event at the Calgary Stampede today.

"We are saddened to report that during today’s rodeo, a steer sustained a severe injury that was untreatable and as a result was humanely euthanized," said the Stampede in a release. 

It happened during the last run of today's steer wrestling event in front of thousands of spectators.

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This steer was fatally injured in today's rodeo at the Calgary Stampede after being wrestled by cowboy Zane Hankel. The Stampede says only two steers have died in the event in the last decade. (CBC)

The cowboy competitor immediately called for assistance after the steer failed to rise.

Rodeo workers surrounded the steer and competitor with a tarp before the animal was rushed off the field on a stretcher. Three veterinarians on scene assessed the situation and determined the injury was not treatable.

Calgary Stampede officials say the run appeared to be normal, but independent livestock specialists will be reviewing the event video to determine if there were any contributing factors.

The Calgary Stampede says more than 1,000 steers have participated in the event over the past decade, and only one other animal has been fatally injured.

The Vancouver Humane Society called for the suspension of steer wrestling following the animal's death. The animal advocacy group has been a longtime critic of rodeo events at the Calgary Stampede.

'Very rare,' says cowboy 

Zane Hankel, the cowboy from Redcliff, Alta., involved in the run, said he had no idea the steer was hurt at first. He thought maybe the animal's horn got stuck in the ground.

"We never intentionally hurt any of these animals. We use them lots throughout the year," said the cowboy who has been wrestling steers since Grade 10.

"We run over anywhere from 150 to 200 steers a year, and it's very rare to ever seen one get hurt — ever."

Stampede veterinarian Dr. Greg Evans said he decided to euthanize the animal because, in addition to the severe neck injury, it had complete paralysis and some systemic system failure.

But, he said, the injury appears to have been completely accidental.

"From my vantage point, this run was totally normal," said Evans.

A post-mortem will not be performed.