Backeman Hannius, Linda Marie
- Department of Applied Animal Science and Welfare, Swedish University of Agricultural Sciences
Abstract
Social interactions in group-housed pigs have important consequences for animal welfare, yet individuals differ substantially in their behavioural expressions and responses to social challenges. This thesis investigated how early social environments and genetic line influence behavioural development, social responses and welfare-related outcomes in group-housed gilts and sows. Across a series of experimental studies, gilts from two genetic lines were followed from early rearing throughout gilt development and into first parity, with variation in social experience created by early and late social mixing treatments. The behaviour of individuals post-weaning, including activity, pen use and social interactions, was assessed, and later-life responses to unfamiliar conspecifics were evaluated in standardised paired interaction tests together with lesion outcomes to indicate the intensity of social challenges. An observational study in commercial herds described the prevalence and distribution of lesions, lameness and body soiling under practical production conditions. Early social experience, in which piglets were mixed with a litter from a neighbouring pen during lactation, influenced behavioural expression after weaning and later influenced how females responded to social challenges, but did not consistently reduce aggression. Later social experience, involving regrouping with unfamiliar individuals after weaning, modified aspects of behavioural strategy during paired interactions. Genetic line was repeatedly associated with the type of initiated social behaviour, with response patterns and lesion outcomes indicating line-specific differences in social behaviour expressed across life stages and varying by social interaction type. Variation in welfare-related outcomes observed in commercial herds further demonstrated that lesion occurrence and other indicators varied with production stage and management conditions. In conclusion, social behaviour and welfare-related outcomes in group-housed breeding females reflect the combined effects of genetic background and social experience across life stages. The findings highlight the importance of considering how individuals initiate, respond to and regulate social interactions when evaluating welfare in systems characterised by repeated social mixing and provide relevant knowledge for assessing and developing management practices in modern pig production.
Keywords
pig; gilt; sow; social behaviour; group housing; social experience; genetic line; behavioural strategies; animal welfare; lesions; gris; gylta; sugga; socialt beteende; grupphållning; social erfarenhet; genetisk linje; beteendestrategier; djurvälfärd; sår
Published in
Acta Universitatis Agriculturae Sueciae
2026, number: 2026:24
Publisher: Swedish University of Agricultural Sciences
SLU Authors
UKÄ Subject classification
Animal and Dairy Science
Behavioral Sciences Biology
Publication identifier
- DOI: https://doi.org/10.54612/a.3q29jgrnfv
- ISBN: 978-91-8124-241-6
- eISBN: 978-91-8124-271-3
Permanent link to this page (URI)
https://res.slu.se/id/publ/146291