While aggression among sows in group-housing systems is inevitable, grouping sows by parity can improve young sows’ performance and well-being, according to Yuzhi Li, swine scientist, West Central Research and Outreach Center, University of Minnesota. Group-sow-housing management strategies should focus on protecting vulnerable sows from aggression.

Since young sows generally average only 75 percent of the bodyweight of mature sows, they are usually subordinate in group-housing systems. When sows of all parities are housed together, young sows avoid conflicts while attempting to obtain feed and water, which leads to inadequate feed intake and reproductive failure. As a result, they lose most fights at mixing, suffer more injuries and have higher cortisol levels than mature sows. 

This aggression can result in young sows being culled prematurely, reducing a sow herd’s lifetime productivity and production efficiency.

According to Li, it may be appropriate to house first-parity sows in gilt pens rather than in sow pens to prevent these young sows from experiencing aggression so that their performance and welfare would not be compromised in group-housing systems.

Although young sows in gilt pens were involved in more fights, they won more fights compared to young sows in sow pens, Li notes.

The young sows housed in gilt pens had greater farrowing rates and gained more weight during the gestation period compared with young sows in sow pens. The performance improvement can contribute to improved lifetime productivity and improved production efficiency in group-housing systems.