Tail-biting in growing-finishing pigs with intact tails: evaluating group size and litter origin

Tail-biting is a persistent welfare and production challenge in swine systems, resulting in pain, stress, impaired growth, and economic losses. Despite extensive research, the behavior remains difficult to predict and prevent. The overarching objective of this dissertation was to investigate social and behavioral risk factors of tail-biting in pigs with intact tails, using group-level and individual-level approaches, and to evaluate associated welfare outcomes across diverse contexts. Two major research projects were conducted, which are presented across four data-driven chapters that collectively address the social, behavioral, and physiological mechanisms underpinning tail-biting.The first study examined the influence of group size by comparing small (9 pigs) and large (18 pigs) pens. Pigs housed in smaller groups experienced more frequent removals due to tail damage, whereas larger groups altered the progression and expression of outbreaks but did not mitigate overall risk. Building on these findings, a framework was developed to classify pigs as biters, victims, or controls. This approach demonstrated that roles were fluid, with some pigs occupying dual roles, and revealed that gilts were more frequently identified as biters, underscoring individual-level variation in the expression of damaging behavior. The second study evaluated litter origin as a proxy for social structure and relatedness by comparing pens of littermates (LIT), two-litter groups (2LIT), and non-littermates (NONLIT). Pens of 2LIT pigs exhibited the highest frequency of outbreaks and most severe injuries relative to LIT and NONLIT pens. Within these groups, biters displayed elevated concentrations of tumor necrosis factor-alpha (TNF-α), suggesting a physiological link between stress responsiveness and biting behavior. These results indicate that partial relatedness among penmates can create social instability that elevates risk and highlights the potential utility of immune markers for identifying pigs predisposed to biting. Finally, data across both projects were integrated to evaluate the spatiotemporal context of outbreaks. Tail-biting events occurred most frequently in the central pen area, typically when biters were standing and victims were lying sternal, during periods of low feeder occupancy. Events peaked from late morning to mid-afternoon, reflecting predictable daily activity patterns. These insights provide practical context for targeted monitoring and early intervention. Collectively, this work advances understanding of the social, behavioral, and physiological mechanisms underlying tail-biting in growing–finishing pigs with intact tails. By integrating group-level factors, individual roles, physiological profiles, and event-level dynamics, this dissertation contributes knowledge that can inform precision livestock farming strategies aimed at earlier recognition and intervention. Improved early detection has the potential to reduce tail-biting, enhance pig welfare, and support the long-term sustainability of swine production systems.

Author dc:creator

• Archer, Courtney

• Biters
• Group Size
• Litter origin
• Swine welfare
• Tail-biting
• Victims

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/11299/278788

OAI identifier oai:identifier

oai:conservancy.umn.edu:11299/278788