Rein man: did Dustin Hoffman harm horses in his new drama?

Big-budget HBO series targeted by campaigners after two star performers had to be put down

Animal rights activists have criticised Dustin Hoffman's new television drama about horse-racing – Luck – after two of its equine performers had to be put down when they were injured on set.

"The two racehorses stumbled and fell during short racing sequences," the American Humane Association (AHA) said. "The horses were checked immediately afterwards by on-site veterinarians and, in each case, a severe fracture deemed the condition inoperable. The decision was that the most humane course of action was euthanasia."

The first fatality occurred during the filming of the pilot episode of Luck, which included a fictional scene of an injured horse being put down. The second animal was put down during filming of the seventh episode, though details of the deaths only recently came to light after neither episode displayed the AHA certification confirming that "no animals were harmed" in the making of the shows.

HBO, the US broadcaster behind Luck, said filming was suspended after the second death "while the production worked with AHA and racing industry experts to adopt additional protocols specifically for horse-racing sequences". These included "the hiring of an additional veterinarian and radiography of the legs of all horses being used by the production".

However, the second death prompted Peta to renew its call for existing safety rules to be tightened to protect animals in film and TV productions.

"Breakdowns don't just happen," Kathy Guillermo, the vice-president of Peta, told Entertainment Weekly. "Horses break down for a reason. Often, it has to do with the condition they're in at the time they're put on the track."

Hoffman produces and stars in the critically acclaimed Luck, which aims to shed light on the dark side of thoroughbred racing. Having attracted more than three million viewers for its first episode, the 10-part show has just been given a second season.

"While [Luck] does acknowledge how many thoroughbreds suffer catastrophic breakdowns and how horses are routinely doped, two dead horses in a handful of episodes exemplify the dark side of using animals in television, movies, and ads," said a blog post on the Peta website.