WASHINGTON – Increasingly, food industry stakeholders are moving away from direct or indirect use of gestation crates to house pregnant sows, but crates and other methods of housing sows have their benefits and challenges, according to a report from the US Department of Agriculture.

Individual gestation crates have been used in hog production for the last 30 years, according to USDA. A typical crate measures 2 ft. by 7 ft. (or 14 sq. ft.), and was adopted by the industry to address “hierarchical swine behavior.”

“Female swine, in particular tend toward aggressive behavior to establish dominance when they are housed in groups,” the USDA report said. “Such aggression can cause serious injury to less-dominant females and to unborn piglets.”

Gestation crates minimize aggression and threat of injury, according to the report. Crates also facilitate individualized care, feeding and monitoring. However, pregnant sows are severely constrained in the crates. They are capable of limited side-to-side and back-and-forth movement. But they are totally unable to turn themselves around, according to USDA.

But crates also provide crucial safety features for sows when they are most vulnerable to aggression and injury. In group sow housing, newly bred sows are crated for roughly 30 days “to ensure proper embryo implantation.” This is common practice in the US and European Union, according to USDA. Also, sows are crated five days before farrowing (giving birth). Also, sows are moved to farrowing crates that allow for the female to nurse the litter while preventing injury to the piglets through crushing or smothering, USDA said.

Group sow housing presents benefits and challenges. No typical group sow housing scheme exists in the US, USDA said, so design characteristics of existing group housing varies widely. Also, the number of animals in a group can range from five to 100, and they can remain in a static group —all the animals entering the pen together — or in a dynamic group in which animals can enter and leave the group. The size of the group and space allocation directly impacts how the animals will be fed, and this presents a serious challenge to producers.

“Feeding animals in a group setting presents serious challenges given the tendency of swine toward aggression, particularly at feeding time,” USDA said in its report.

However, comparative studies of sow housing show that productivity is not affected by housing type. This is positive news for US producers who may equate group housing with lower sow productivity. Studies also show that animal handling and management skills are crucial to maintaining productive sows in pens. Also, no animal science or studies prove conclusively that animal welfare is improved by switching pregnant sows to group housing.