The plan was for six 900-kilogram bulls to run down Bay Street between Wellington and King Streets on Tuesday. The event would have served as a precursor to the fair's Nov. 2 opening day at Exhibition Place.
However, organizers were forced to cancel the run after the city denied permit applications.
Elizabeth Glibbery, the city's manager of animal services, says the event violated bylaws.
"Under the bylaw there is a provision for exceptions — under educational and for film production, however the purpose and intent of this event is for promotional purposes and, therefore, does not meet the exception," Glibbery said in an email.
"This would have been a significant and dangerous precedent in respect to prohibited animal use in the city."
The decision did not sit will be organizers, who said proper precautions had been taken.
"I can say that it's disappointing," said the fair's director of marketing, Rachel Woodman. "We worked for many months closely with the city, with police services and animal services to plan this."
Woodman says despite complaints from animal activists, animal and public safety has always been a priority.
"It was not an event that was planned to cause stress to the animals or to the city at any point," she said. "We ensured that we had the safety of the animals as a priority because we would never treat animals poorly."
The fair will run until Nov. 11, and the bulls will be featured in a rodeo Nov 4.
It will also continue to host the traditional horse shows, agricultural competitions and animal exhibitions — and a celebrity chef challenge.