PLEASANTON, Calif. (AP) -- The nation's second-largest grocery chain says it will adopt purchasing policies that favor more humane treatment of pigs.

Safeway Inc. announced Monday that it's planning to stop buying from suppliers that use pig gestation crates.

Most pork currently comes from sows confined during their four-month pregnancies in narrow crates. Animal welfare activists have pushed for using open pens.

Other corporations such as McDonald's and Burger King also plan to buy pork from pigs not kept in crates.

Safeway spokesman Brian Dowling says the chain already buys some pork from producers who are phasing out gestation crates. The Pleasanton, Calif.-based company has not set a deadline for going completely crate-free.

The Humane Society of the United States has been working with the industry to improve welfare of caged chickens and pigs.

Copyright 2012 The AP.