Getting around social status: Motivation and enrichment use of dominant and subordinate sows in a group setting

Gestating sow motivation for enriched environments is unknown, but is essential knowledge for developing housing that addresses animal welfare concerns. This study investigated whether the motivation of gestating sows for access to an enriched group pen (containing a rubber mat, straw, compost, and cotton ropes), and their behavior while in the pen, would differ due to social status. Motivation was measured using an operant panel and behavioral measures were obtained to test our hypotheses. Dominant and subordinate sows were similarly (58.38 +/- 21.54 presses vs. 96.88 +/- 48.30 presses [raw data], respectively; P=0.72) and moderately (comparable operant responding to sows that had consumed 25-50% of their ad libitum diet) motivated for access to an enriched group pen. However, sow social status impacted aggression (P=0.007), enrichment use (P=0.001), and inactivity (P=0.002): where dominant sows were more aggressive (0.61 +/- 0.29 vs. 0.06 +/- 0.03 [raw data]; P=0.008) and spent more time using enrichments (54.58 +/- 6.02 vs. 29.57 +/- 5.56 [raw data]; P=0.001) upon entrance to the pen, while subordinate sows were more frequently displaced from enrichments (P < 0.001) and spent more time inactive (59.82 +/- 6.23 vs. 37.44 +/- 5.51 [raw data]; P=0.003). Sow social status affected the pattern of enrichment use over the course of the day (P=0.02), where subordinate sows increased their use of enrichments the following morning during non-peak times (P=0.001). These findings demonstrate that regardless of social status, sows were able to access enrichments and valued an enriched group pen. Sow social status has the potential to greatly alter the effectiveness of enrichments in group settings and will become an increasingly important consideration as scientists and producers explore welfare friendly alternatives to barren sow housing. (C) 2011 Elsevier B.V. All rights reserved.