Factors influencing farmer willingness to reduce aggression between pigs.

Aggression between pigs remains an important animal welfare issue despite several decades of research. Aggression is primarily caused by the unstable social structure created by regular regrouping, as pigs fight in order to re-establish dominance relationships. Several strategies to reduce the occurrence or intensity of aggression at regrouping have been identified. However, these strategies are insufficiently adopted in commercial practice. Uptake of livestock welfare research relies on various stakeholders being willing to recommend or adopt changes to farm structure or management (e.g., veterinarians, researchers, farmers). We surveyed 122 UK and Irish pig farmers on their attitudes and practices regarding aggression between growing pigs. A structural equation model was used to investigate the factors that influence farmer willingness to implement aggression control strategies, to identify targets for initiating a change in practice. The majority of farmers mixed pigs at least once during each production cycle, and had tried at least one strategy to reduce aggression in the past. Strategies were considered to be moderately useful, but farmers expressed limited willingness to use them again in the future. Willingness to implement aggression control strategies was directly influenced by (1) their beliefs about the outcome (p < 0.01), and (2) their perceived possibility to make a change (p < 0.01). Furthermore, willingness was indirectly influenced by (3) their perceptions of the problem (p < 0.001) and (4) relevant stakeholder groups (p < 0.01). Veterinarians had the greatest influence on farmer behaviour when compared to all other stakeholder groups (p < 0.05). We recommend that researchers employ a combination of approaches to encourage a change in practice. Aggression control strategies should be tested outside of the highly controlled research setting, in order to establish their outcomes and ease of practical implementation under commercial conditions. The economic consequences of different strategies should be calculated, in order to advise farmers on the most cost-effective solutions and their impacts on farm profitability. Finally, information on the consequences of aggression, how to recognize it as a problem and how to control the issue should be effectively transferred into industry by researchers. Knowledge transfer should be directed not only at farmers but at various stakeholder groups, with special emphasis on veterinarians. The Structural Equation Model approach could be useful to understand farmer decisions with regards to other specific and entrenched animal welfare issues.