The 22nd fatality at a famed Southern California racetrack since Christmas has cast a further cloud over its future.
A three-year-old filly named Princess Lili B was euthanised on Thursday after breaking both of her front legs at the end of a half-mile workout at Santa Anita Park.
Earlier this month, Santa Anita cancelled racing after the 21st fatality and brought in a surface expert to determine what had caused the spike in deaths.
The track only reopened for training again this week, while the scheduled resumption of racing next weekend could be postponed.
Following the latest death, Santa Anita Park said it would ban the use of drugs and whips during competitions.
The restrictions would be the first of their kind in the United States and came on the day federal legislation was reintroduced that would ban race-day medication and increase out-of-competition testing nationwide.
“What has happened at Santa Anita over the last few weeks is beyond heartbreaking,” Belinda Stronach, chairman and president of Santa Anita owner the Stronach Group, said in a statement announcing the changes.
“It is unacceptable to the public and, as people who deeply love horses, to everyone at The Stronach Group and Santa Anita.
“The sport of horse racing is the last great sporting legacy platform to be modernised. If we expect our sport to grow for future generations, we must raise our standards.
“We are taking a step forward and saying, quite emphatically, that the current system is broken.”
Stronach said the changes would also apply to Golden Gate Fields, which is located in the San Francisco Bay Area.
Animal rights group People for the Ethical Treatment of Animals (PETA) applauded the announced changes but said horse racing must ultimately “go the way of the animal circus”.
“PETA thanks Santa Anita for standing up to all the trainers, veterinarians, and owners who have used any means — from the whip to the hypodermic syringe — to force injured or unfit horses to run,” the group’s senior vice president Kathy Guillermo said.
“This is a watershed moment for racing, and PETA urges every track to recognize that the future is now and to follow suit.”