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Behavior and performance of pigs previously housed in large groups
1West Central Research and Outreach Center, University of Minnesota, Morris 56267, USA. yuzhili@morris.umn.edu
Journal of Animal Science
|December 23, 2008
Summary
Grouping unfamiliar pigs, even those from group-housed sows, increases aggression and injuries, initially reducing pig performance. Social familiarity is key for pig welfare and optimal growth in group-housed settings.
Area of Science:
- Animal Science
- Animal Welfare
- Ethology
Background:
- Group-housing of lactating sows is becoming more common.
- Understanding the welfare and performance implications of mixing pigs from these systems is crucial.
Purpose of the Study:
- To evaluate the impact of social familiarity and initial body weight (BW) uniformity on pig performance and welfare.
- To assess aggression, injuries, and growth in pigs mixed based on familiarity and BW variation.
Main Methods:
- A 2x2 factorial design with 180 pigs (8 weeks old, ~23 kg BW) was used, testing social familiarity (familiar vs. unfamiliar groups) and BW uniformity (uniform vs. variable).
- Aggression, activity, and injuries were observed/assessed during the initial days post-grouping.
- Body weight gain and feed intake were monitored over 14 weeks.
Main Results:
- Unfamiliar pigs exhibited significantly more fighting, higher injury scores, and reduced feeding time immediately after mixing compared to familiar pigs.
- Average daily gain (ADG) and average daily feed intake (ADFI) were reduced in unfamiliar groups during the first 6 weeks.
- BW variation exacerbated aggression-induced injuries in unfamiliar groups but did not affect familiar groups.
Conclusions:
- Mixing unfamiliar pigs, even from group-housed sows, leads to significant welfare concerns including increased aggression, injuries, and initial performance deficits.
- Promoting social familiarity among pigs before or during mixing is essential for mitigating negative welfare outcomes and ensuring optimal performance.
