People for the Ethical Treatment of Animals sent out a release Thursday asking the British royals to cancel their plans to visit the stampede, the Canadian Broadcasting Corp. reported.
"The Calgary Stampede has long been synonymous with animal abuse," PETA President Ingrid Newkirk wrote, citing the use of electric shock prods, which are illegal in Britain.
The animal advocacy group has been a persistent opponent of the Calgary Stampede, the CBC says, contending the rodeo events often lead to animals being injured or killed for the sake of entertainment.
"The eye of the world rests on the duke and duchess," Newkirk wrote of the royal couple, "and they are walking into a hotbed of controversy over cruelty if they visit this vile rodeo."
The couple's trip across Canada began Thursday and they are scheduled to arrive in Calgary Wednesday.