TORONTO -- Pork industry experts say most of what is seen in a hidden camera investigation at a Manitoba hog farm is widely accepted practice.

The video, filmed by an investigator working with the group Mercy for Animals Canada, shows what the group calls "extreme cruelty," including piglets being slammed down onto the floor by staff.

But the Animal Care Review Panel, made up of a University of Manitoba animal sciences professor, an Ontario Veterinary College professor and a research scientist, says that's a humane way to euthanize piglets.

The panel, formed by the Center for Food Integrity, a U.S.-based organization representing farmers, food processors and retailers, said most of what's in the video is widely acceptable and humane.

However, it did condone scenes that appear to show workers euthanizing a piglet by swinging it into a metal post and kicking and slapping a pig that is having trouble getting up.

Mercy for Animals Canada is calling on major grocery chains to stop carrying meat from producers who use gestation crates, tiny stalls in which sows spend most of their lives.

Dave Wilkes, senior vice-president of the Retail Council of Canada's grocery division said stakeholders are in the process of developing a code of practice for the care and handling of pigs, and issues in the video such as gestation crates are being reviewed.

The video was released after an investigator working with the group Mercy for Animals Canada got a job at a Puratone Corp. farm in Arborg, Man., and spent about 10 weeks filming with a hidden camera.

The footage appears to show pigs bleeding from open wounds in tight metal cages, pregnant pigs with distended, inflamed bellies, and piglets being slammed down on the floor by staff.

The group sent its footage to the office of Manitoba's chief veterinarian, which has said it will be reviewing the video.

The advocacy group said meat from the plant is purchased by Sobeys (TSX:SBY), Loblaws (TSX:L), Metro (TSX:MRU.A), and Walmart Canada. Wilkes, speaking on behalf of the retailers, said when things go wrong immediate action must be taken.

"Our members and everybody that works with hogs must treat them with respect and compassion," he said.

"As an industry right throughout the supply chain we have zero tolerance for animal abuse."

Puratone CEO Ray Hildebrand has said in a statement that the company is "disturbed" by the images, which he added do not reflect its animal care rules.

Hildebrand has said an investigation is underway and that "corrective actions" will be taken as a result of the video.