More than 500 horses expected to compete in the chuckwagon races at the 2011 Calgary Stampede will receive microchip implants that will allow veterinarians to monitor the animals’ health before and after each race.

The annual Calgary Stampede features rodeo-style competitions and livestock exhibitions. The Stampede’s GMC Rangeland Derby Chuckwagon race pits four teams of horse-drawn wagons against each other in a series of elimination races over several days. Traditionally, each team has consisted of four wagon horses and four horses carrying outriders.

Some animal welfare groups have long criticized the chuckwagon races on grounds that the events put horses under extreme stress and risk for injury and death. Last year, a total of six horses died in separate Stampede rodeo events. Of those, four Thoroughbred horses died in connection with the chuckwagon races.

In February, the Stampede adopted new rules intended to improve safety of both equine and human race participants, including mandatory veterinary inspections for horses used in chuckwagon races upon arrival, prior to each race, and after each race among other rule changes