The former manager of a large Oklahoma pig farm has been charged with felony animal cruelty for his role in beating and smashing to death pigs being fattened for slaughter.

The unusual prosecution was brought against a manager for Seaboard Farms Inc., in Texas County, Okla., which in the past decade has become a center for the nation's growing pork industry.

According to District Attorney Donald E. Wood, four counts of cruelty to animals, a felony, were filed against Alejo Pena based on videotapes supplied by an undercover investigator for the animal rights group People for the Ethical Treatment of Animals (PETA).

"There are ways to treat and slaughter farm animals in Oklahoma, and I think the videos showed the way they did it violated the statute," Wood said.

Animal rights activists have charged that large factory farms like Seaboard encourage animal cruelty, while pork producers say they set and maintain high standards for the treatment of their animals.

In a complaint filed in May with Wood's office, an attorney for PETA outlined the contents of the video, which was made late last year. Among the charges were that Pena and other Seaboard workers beat pigs with the hooked end of a metal gate rod and a hammer, that they left fatally sick pigs alone to die, and that they killed some young pigs weighing up to 40 pounds by raising them above their heads and slamming them against the floor.

"I know some people don't think animals raised for slaughter are worthy of any particular kind of good treatment," said attorney Mort Welch, who handled the case for PETA. "But I think it would be very hard for most people to look at those videos and say what those men were doing was okay."

Each charge carries a maximum punishment of five years in prison and a $500 fine.

Welch said criminal charges involving abuse of farm animals were unusual, and that Oklahoma was one of only a few states that even allowed them to be brought.

Seaboard spokesman Gary Reckrodt said that his company, the nation's third largest pork producer, is cooperating with authorities.

"We have a zero tolerance policy for animal abuse, and it is grounds for immediate dismissal," he said. "If this did happen, then it would be a very isolated case."

The charges against Pena were filed Aug. 31, but became publicly known Friday. Wood said Pena, who was released on $75,000 bond, was charged when his office learned he might be leaving the area. Wood said his office was continuing its investigation and that additional charges could be filed. Pena's attorney did not return a call for comment.

PETA officials sent their undercover investigator to the Guymon farm as a worker, and he documented the alleged abuses with a small video camera strapped to his body. A similar investigation by the group in North Carolina two years ago also resulted in felony charges of animal cruelty against three farm workers. Two of them pleaded guilty to reduced charges.

PETA spokeswoman Lisa Lange called the Oklahoma charges "a step in the right direction."

"It sends out the message that hammering piglets, slamming them into the ground and neglecting them when they can't move is animal cruelty, even when it takes place on a factory farm," she said. "This is so important because we understand this is more the rule than the exception."

When PETA gave its videos to the Texas County district attorney in May, it also provided expert witness statements from animal welfare specialists. Temple Grandin, who advises fast-food chains in animal welfare and slaughtering issues, said the tapes show "incidents of very severe animal abuse." University of Pennsylvania professor James Serpell, who holds an endowed chair in ethics and animal welfare, said they show "some of the worst episodes of gratuitous violence and cruelty toward animals I have ever witnessed."