“Luck,” HBO's new gritty, realistic (if somewhat confusing) horse racing drama, is in hot water with PETA, after it became public that two horses died during the filming of the series’s first season.

As Entertainment Weekly reported, the pilot — which fictionalized a horse being injured and euthanized in one scene — did not carry the American Humane Association’s stamp to assure viewers that “No animals were harmed” during filming. That’s because a horse suffered a severe fracture while filming a race sequence and had to be euthanized. The same fate befell a second horse during episode seven’s filming.

PETA claims it reached out to the show’s creator David Milch and HBO before “Luck” began shooting, but did not receive a response: “Perhaps if producers had considered the proved safety protocols that we would have suggested, these horses would still be alive.”

HBO responded to PETA’s concerns in a statement to the New York Observer: “After the second accident, production was suspended while the production worked with [the American Humane Association (AHA)] and racing industry experts to adopt additional protocols specifically for horse racing sequences. The protocols included but were not limited to the hiring of an additional veterinarian and radiography of the legs of all horses being used by the production. HBO fully adopted all of AHA’s rigorous safety guidelines before production resumed.”

The AHA reiterated this statement in a lengthy review of its procedures regarding “Luck.”

PETA, however, is still not satisfied. The organization’s vice president, Kathy Guillermo, told EW they have asked for more information about the horses who died. A petition urging HBO to listen to PETA has been started on Care2 and has garnered over 7,500 signatures since Jan. 30.

Clearly, the racing sequences are vital to “Luck,” which was been renewed for a second season. The Post’s Hank Stuever praised their beauty, writing, “The races are thrillingly shot. The camera adores every ripple of the animals’ muscles. The steam that rises from their gorgeous bodies during a dawn bath. They are stroked and adored and magnificent.”

But he also guessed that the pilot, and the risks the horses take to film the show, would turn some viewers away: “This show necessarily puts its remarkable beasts at the same mortal risk as its deplorable humans, which means animal lovers may also find themselves making a quick exit.”