Secretly taped footage of a U.S. hog farm feeding its sows the ground-up intestines of piglets that have died of a contagious pig virus is stirring up anger among animal rights advocates.

The Humane Society of the United States released footage this week showing piglets dying of PED, or Porcine Epidemic Diarrhea, at the Iron Maiden Hog Farm in Kentucky, where it says more than 900 piglets have succumbed to the diarrheal disease.

The animal rights group says intestines of the piglets are being ground up into "a smoothie" and fed to sows at the farm in a bid to immunize the pigs from the highly contagious disease.

Hog farmers have been struggling for years to get a handle on the devastating PED virus. The illness has killed more than 2 million piglets in 25 states in the U.S. since April 2013.

Here in Canada, the virus is just beginning to emerge and has been reported at 16 farms in Ontario and at one each in Manitoba and Prince Edward Island.

The Humane Society says its footage was captured with hidden cameras by its own investigators earlier this year at the farm.

The group says the practice “appears to be fairly widespread” within the industry but says it’s prohibited by Kentucky state law. The group is calling on state authorities and the U.S. Department of Agriculture to examine the practice and for the USDA to ban it.

But the director of the American Association of Swine Veterinarians tells The New York Times that feeding piglet intestines to sows is legal and safe and doesn’t pose a risk of transmitting the illness to humans.

He adds that other hog farmers are choosing to feed diarrhea from an infected animal to healthy pigs as another way to expose them to PED.

A recently-developed vaccine for PED, called iPED+, is now available in the U.S. The Canadian Food Inspection Agency approved emergency use of the vaccine last month.

The Humane Society’s investigation also found that sows at the farm were kept confined in cramped cages called gestation cages, in which they couldn’t move or turn around.

Wayne Pacelle, president and CEO of the HSUS, says immobilizing sows for their entire lives, feeding dead pigs to live pigs, denying medical treatment to ailing animals “don’t sit well” with consumers.

"This industry is long overdue for a major course correction, and we hope this investigation triggers an examination at what’s happening behind closed doors on factory farms,” he said in a statement.

Recently, more than 60 major food companies, including McDonald’s, Costco, Target and dozens more, have promised to buy pork only from providers that are eliminating the use of the crates.

In Canada, a national group of farmers and animal welfare advocates has drafted a new policy that calls for limits to the use of gestation crates and for mated female pigs to be housed in groups.

As well, the Retail Council of Canada announced in April that eight of the largest Canadian supermarket chains have vowed to work with the Canadian Pork Council to phase out the use of gestation cages by 2022.

Earlier this week, the Canadian Food Inspection Agency announced that it was testing feed pellets to see if contaminated pellets might be playing a role in the outbreak. The results are expected soon.