Kelly Sutherland competes in the chuckwagon races at the High River Rodeo on June 26, 2012 in High River, Alberta.
An animal welfare group wants the chuckwagon races at the Stampede halted after a crash that killed three horses and injured another.
"We think that all the changes that the Calgary Stampede has been publicizing over the past few months that were supposed to make this race safe obviously haven't worked," Peter Fricker, a spokesman for the Vancouver Humane Society, said Friday.
"We think that there's something more fundamentally wrong with the race and we're calling for a suspension of the chuckwagon races and a full and fundamental safety review to be conducted."
Thursday night, the lead horse for a team driven by Chad Harden suddenly went down, taking two others horses with it and sending Harden and an outrider flying through the air.
Stampede spokesman Doug Fraser said Thursday night that the horse that collapsed "experienced a fatal event."
Neither man was hurt but two of the horses had to be euthanized on the track due to their injuries. A fourth horse will require surgery but is expected to survive.
Mr. Fraser said no new information was available Friday regarding what caused the first horse to die or the condition of the horse that survived.
He said the Vancouver Humane Society is an "activist group with an activist agenda" that has always pushed for the chuckwagons to be stopped.
"We rely on the advice from heavy animal experts. We don't rely on the advice from organizations like VHS," said Mr. Fraser.
"Although people have the right to divergent opinions, VHS is certainly not the expert on animal care with respect to large animals."
The Calgary Humane Society has taken a different tack than its Vancouver counterpart when it comes to animal welfare at the Stampede.
It's against using animals for entertainment, but acknowledges the chuckwagon races and rodeo events aren't going away.
"We think that working with the Stampede is the best that we can do to help make these events as safe as possible," said spokeswoman Christy Thompson.
She says humane society officers are on the grounds for all events and are there to help the Stampede make "educated changes" to enhance safety.
"I believe honestly that the Calgary Stampede has worked diligently to make these events as safe as possible."
VHS's Mr. Fricker said the problem that caused Thursday's crash could have been with the nature of the race itself.
"There's just not very much room. They're making very tight turns and they're going at high speed," he said.
Another issue is the physical condition of the horses. He said research has suggested some horses may have legs too weak for their bodies as a result of selective breeding.
"We don't know yet, but those are the kinds of things that we think the Stampede should be looking at, not making what appear to be superficial changes."
The Stampede introduced some new rules last year aimed at making chuckwagon races safer for both horses and competitors. The move came after six horses died in 2010.
All horses are now inspected by veterinarians when the animals arrive at the Stampede and before and after every race. There is also a mandatory rest day after every four days of racing.
The number of outriders that accompany each chuckwagon as it thunders around a dirt track was reduced to two from four to try to avoid congestion. Several riders have been seriously injured over the years.
Mr. Fraser said after the accident that it goes "without saying" that Stampede officials had hoped to complete the 100th anniversary competition without any animal deaths.
"It's a sad situation, but we will investigate the incident to determine what happened in the hopes we can prevent it from happening again," he said.
"These horses are cared for. They are loved by the drivers themselves and there's no question it's a tragedy for these families."