MINNEAPOLIS (WCCO) — A California-based animal rights group is calling on Walmart, the nation’s largest retailer, to stop buying pork from a Minnesota producer.

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Mercy For Animals went undercover at a hog farm in Pipestone and recorded gruesome images they say proves their point.

For 10 weeks a Mercy For Animals activist shot undercover video inside Pipestone System’s Rosewood Farm. The video captures hog handling practices by several workers that the group says constitute animal cruelty.

According to Matt Rice, MFA’s director of investigations, the activist “saw workers slamming conscious piglets headfirst into the concrete to kill them.”

That’s a practice used in the hog industry known as blunt force trauma. Hog farmers say it’s the quickest and most humane way to euthanize undesired, sick, injured, or underweight piglets. But an industry spokesman says other alternative methods are coming into use, including the use of gas containers.

The video also reveals castrations and tail docking on young pigs performed without the use of anesthesia.

But it’s the tight confinement of pregnant sows in what are known as “gestation crates” that Mercy for Animals wants pork retailers to condemn.

Walmart is one of Pipestone’s largest customers.

“Walmart not only has the ethical responsibility but also enormous purchasing power to ensure the pork sold in its stores is not the product of egregious animal abuse,” Rice said.

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Shortly after the video began circulating, Walmart responded to the criticism. Company spokesperson Danit Marquardt said, “We think the animal handling in this video is unacceptable. We are currently conducting our own review of the situation.”

This isn’t the first time Mercy For Animals has taken aim at a Minnesota factory farm. It went undercover at Christiansen Farms, another major hog producer, back in the summer of 2012.

By showing the video, the group’s aim is to create consumer outrage, in the hopes that Walmart finds another source for its pork.

David Preisler is executive director for the Minnesota Pork Producers Association and says the gestation crates are necessary to protect the sows and their young piglets.

“Sows are aggressive animals, and they will fight each other — sometimes, unfortunately, to the death,” he said.

He added that while the Pipestone county attorney found no grounds to file animal cruelty charges at the farm, a worker seen in the video was fired for not following strict animal handling procedures. Others were either reassigned or retrained by the farm.

“We also want people to understand the motive for Mercy for Animals is a vegan society. They don’t want anyone to eat meat, and this is one tactic they employ to reach that end,” Preisler said.

In addition to its dislike for the handling seen in the video, Walmart is also promising to roll out a new farm tracking system in the next several weeks. That, Marquardt says, will make certain that the pork it purchases from farms is “certified to meet the highest standards for the treatment of animals.”

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The images captured in the Mercy for Animals undercover video are extremely graphic and may be disturbing. It can be viewed at: www.walmartcruelty.com