A Review: Aggression Concerns with Group-Housed Sow Well-Being

Abstract

The global trend toward housing gestating sows in group-pens is primarily driven by welfare concerns associated with the use of individual gestation stalls. Despite transition toward group-housing systems, no housing system has scientifically been identified as being better than another based on current notions of sow wellbeing. Both benefits and drawbacks are associated with housing gestating sows either individually or in groups. The main concern associated with group-housing is increased sow aggression that occurs at mixing and around limited resources, including feed and water. Aggression is inevitable and unavoidable upon mixing of unfamiliar sows, but is necessary for establishment of social hierarchy, which helps reduce overall aggression and tension among the group. Unfortunately, if aggression is intense and prolonged it may lead to stress and compromised sow well-being. With few differences in sow well-being identified between gestation housing systems, it seems plausible that the consequences on sow well-being is not only about the stall or the pen the sow is confined to, but the interactive effects of other housing components. In pens, some of the most critical factors to consider include space allowance, group size, time of mixing, and feeding systems/strategies which may directly or indirectly affect various welfare metrics (e.g., lesion scores, aggressive behavior, reproduction). It is imperative to minimize aggression among grouped sows and feeding and management strategies are viable options that can be used to reduce aggression among grouphoused sows, but not eliminate aggressive encounters. Therefore, the focus of this review is to examine the different feeding and management strategies that can be used to mitigate the drawbacks of grouping housing sows, while improving performance, productivity, and well-being.