Another quick-service chain has committed to using only gestation-free pig crates. Jack in the Box Inc., which operates nearly 3,000 Jack in the Box and Qdoba restaurants, announced it will source only stall-free pork by 2022.

Jack in the Box outlined its policies in a new "Animal Welfare Report" online.

The company states it has evaluated scientific literature documenting the pros and cons of sow environments and has consulted its suppliers and animal welfare experts on the issue.

"While experts generally agree that the most critical issue in ensuring humane treatment of gestational sows is not the housing system, but rather the animal husbandry practices of those that care for the sows, we believe group housing allows for greater movement for sows. In 2012, we informed our pork suppliers of our goal to source all pork from supply systems in which pregnant sows are cared for in a group housing environment instead of gestation stalls. We have begun discussing with our suppliers how they will complete such a transition by the end of 2022," the report says.

Also included in the report are the company's expectations of its suppliers in regards to other animal welfare issues, such as:

• They must actively maintain animal-welfare programs in facilities involved in the direct handling, transportation, or production of livestock and poultry. These programs must be based on recognized best practices specific to the applicable industry, such as cattle, pigs and poultry.
• Our suppliers are expected to source product only from facilities that annually pass third-party audits based on applicable industry standards for manufacturing practices, including food safety and animal welfare.\
• Facilities involved in animal and bird handling must verify compliance with their animal-welfare programs via regularly scheduled self audits. Deficiencies must be addressed immediately.
• Supplier employees involved in animal and bird handling must receive animal-welfare training upon hire, and must receive on-going training at least annually. We encourage suppliers to recognize and reward employee compliance with respectful handling practices.
• Suppliers must use ramps and unloading areas that are designed to facilitate smooth, safe and efficient loading and unloading of animals.
• We prohibit any use of electric prods on an animal's sensitive areas.
• Suppliers must provide ready access to water and food.
• Suppliers must provide veterinary care for their animals.
• During holding at processing facilities, animals must be able to move about easily, and feed cannot be withheld for more than 24 hours.

Subway, McDonald's, Tim Hortons, Burger King, Sonic, Wendy's and other chains have also committed to the use of more humane cages recently. Nine U.S. states have passed laws to ban the gestation crate confinement of mother pigs.

Read more about the supply chain.