The changing face and associated drivers of research on welfare of the gestating sow

Gilts prefer an open pen to a stall

Stalls or crates are a very common type of housing used on pig farms that restrict an animal's movement. How this confinement impacts the animal's affective states is seldom investigated. We conducted a preference test over 7 days where trios of gilts (n = 10 trios, 27.4 ± 1.5 weeks old) had free access between individual self-locking stalls (~ 1.2 m2) and a shared open area allowing 2.8 m2/animal (71% of total area). Gilts had access to ad libitum feed and water both inside the crates and in the open area. After 7 days, personality traits of the animals were assessed with open field (OF) and novel object (NO) tests. Principal Component Analysis (PCA) yielded two main components, which we defined as Passivity and Engagement. The median time spent outside the crate was 95.2% as 21/29 of the gilts exhibited a significant preference for pen over crate during the 7-day trial (p < 0.05). Passivity had no relationship with time spent in the open area, but engagement during OF/NO was associated with less use of the open area (OR = 0.39, 95CI = [0.25, 0.60]). Interestingly, gilts were likely to spend less time in the open area at nighttime compared to daytime (Odds Ratio = 0.49, 95CI = [0.40, 0.60]), as well as experimental days passed (OR = 0.70, 95CI = [0.66, 0.73]). During the first daytime and nighttime, 1/29 and 2/29 animals preferred the crate respectively, whereas by the last daytime and nighttime 5 and 9 gilts preferred the crate respectively (p < 0.05). While both intrinsic (personality) and extrinsic (time of day, experimental day) factors appear to influence the gilt's housing preferences, most gilts significantly prefer an open area to a crate when free access is provided between the two. A smaller subpopulation of animals developed a preference for stalls but still utilize both the stall and the pen throughout the day.

The Role of Environmental Enrichment and Back Fat Depth in the Intensity of Aggressive Behavior Performed by Sows during the Establishment of the Dominance Hierarchy

For sows introduced into new groups, the aggressive behavior associated with establishing a social hierarchy represents a period of severe stress. The aim of this study was to investigate the effect of providing sows with an improved pen environment (straw in racks and ropes) on aggressive behavior after mixing and to understand the role played by sow back fat thickness and parity order. At 29 d post-service, sows were mixed into IMPROVED or CONTROL pens with individual feeding stalls (6 groups/treatment, 20 sows/group). Aggressive behavior was recorded for 2 h at mixing (T0) and 24 h (T1) and 3 weeks post-mixing (T21). Overall, the sows in the CONTROL pens performed more fighting behavior compared to the IMPROVED sows (p < 0.001). This difference was significant only at T21 (p < 0.001). Additionally, the sows in the CONTROL pens generally initiated more aggressive behaviors than the sows in the IMPROVED pens (p = 0.02). The sows with a low back fat thickness initiated more aggressive behaviors, but parity had no significant effect on any of the aggressive behaviors. These results indicate a beneficial effect of improvements to the pen environment on the aggression performed by group-housed sows between the time of mixing and three weeks later. The effect was reduced on the day of mixing, which is in accordance with the necessity for sows to employ aggression to establish the dominance hierarchy.