CANOVANAS, PUERTO RICO - For thoroughbreds in this U.S. Caribbean territory, being fast enough to win, place or show is a matter of life and death -- losers often don't even make it off the racetrack grounds alive.

More than 400 horses, many in perfect health, are killed each year by injection at a clinic behind the Hipodromo Camarero racetrack, said chief veterinarian Jose Garcia. The Associated Press on Friday examined clinic log books that confirmed Garcia's account.

The handwritten logs list the names of the horses, the trainers, the date of execution and the dosages of lethal drugs. Garcia allowed an AP reporter to view the logs but prohibited him from taking notes or photographing the pages.

Unlike on the U.S. mainland, where many former racehorses are retrained for riding or sent to refuges, the animals have few options in Puerto Rico. Owners say caring for and feeding a losing racehorse is too expensive.

"If it doesn't produce, after a while I give it away or I kill it," said Arnoldo Maldonado, 60, a businessman who races about five horses a year. "It bothers me, but it has to be done because there is no money to pay for them. ... I'm not going to keep losing."

The killings also bother veterinarians who carry them out.

While many horses are unsuitable for adoption because of injuries or bad tempers, far more could be rescued than the current few dozen a year, Garcia said.

The veterinarians at the racetrack clinic have an informal system of contacting farms and breeders about a possible home for the animal when a healthy horse comes in to die. But so far there are no programs such as the U.S.-based Thoroughbred Retirement Foundation, which rescues horses coming off the track.

The racehorses put to death in Puerto Rico are not being killed because they have suffered a serious injury, like Eight Belles, the filly euthanized after breaking both front ankles in the Kentucky Derby on May 3. Here, even when a second home is available, veterinarians say that some owners want losing horses executed anyway -- some to save money, others for revenge.

"You'll get a few owners who get so upset, they just want the horse dead," said veterinarian Shakyra Rosario.