4 Calgary Stampede horses die in 2015 chuckwagon races

An outrider horse was euthanized after it was injured during Sunday's Calgary Stampede chuckwagon races, making it the fourth horse to die during this year's Rangeland Derby.

"When we do our debriefing post-Stampede, [we will]look at all of thatand determine whether there was anything we could have done better, if there's any rules that might need to be changing," saidStampede chairman Bill Gray."But certainly we don't like it, we don't tolerate it. We're unhappy about it, actually."

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The animalbelonged toDave Gallowayand wasinjured at the end of the first heat.

Stampede officials say there was no contact made with another horse or wagon.

"It's really upsetting to lose Ezzy," said Galloway in a release. "I try to keep my barn calm, but Ezzy was exceptionally calm.He was my fastest outriding horse and racing, for him, was effortless."

The16-year-old thoroughbred was owned byGalloway for four years.

"The horse's injury was virtually the same as that of another outrider horse on July 11," said Stampede officials in a release."Suspensory ligament rupture is most commonly seen in race horses and occasionally seen in other types of sport horses."

2 horse deaths due to driver error

Two other horses were euthanized following separate chuckwagon racing incidents earlier in the week.

Ahorse belonging to chuckwagon driverLayne Bremner suffered a broken leg during the sixth heat of the Rangeland Derby on July 4, while acrash lastMonday left one of driver B.J. Carey's horses with a serious injury to a joint above its hoof.

Driver error is being blamed for the two deaths.

The Stampede brought in new rules in 2011aimed at making chuckwagon racing safer for the horses and competitors, reducingthe number of outriders runningalongside each chuckwagon fromfour to two.

All horses are microchipped to track their health and racing records, and are not allowed to race more than three days in a row.

Eachhorse isinspected by veterinarians when the animals arrive at the Stampede, and before and after every race.