MINNEAPOLIS (AP) - Costco Wholesale Corp. has joined a growing list of retailers and restaurants in asking suppliers to phase out tight confinement pens for pregnant sows.

The company acted after an animal welfare group shot an undercover video showing conditions at one of the chain's pork suppliers.

Gestation stalls have been a major target of groups like Mercy for Animals and the Humane Society of the United States.

Mercy for Animals had been preparing to release a video shot in a sow barn at Minnesota-based Christensen Farms. Costco then gave the group a letter it sent to its pork suppliers Tuesday urging a phase out of the crates by 2022. The group supplied the letter to The Associated Press.

Mercy's director of investigations, Matt Rice, says he commends Costco.

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