An interdisciplinary approach to understanding antimicrobial use on sheep and beef farms in the UK

There is currently a lack of evidence on: how antimicrobials are used on sheep and beef farms in the UK, the presence of antimicrobial resistance in sheep and beef cattle, and farmer and veterinarian decision-making around antimicrobial use in sheep and beef cattle. This thesis comprises of seven studies which attempt to address these evidence gaps using a multidisciplinary, mixed-methods approach. Study 1 used a mixed-methods approach to evaluate farmers' antimicrobial recording against the contents of medicine bins. Results showed that the medicine records may be inaccurate and measured less antimicrobials than the medicine bins. Study 2 used disk diffusion testing and different interpretation methods to identify patterns of antimicrobial resistance on sheep and beef farms in England and Wales. The key findings were that antimicrobial resistance appears to be low, and the use of species-specific cut-off values may be more appropriate for interpretation of non-susceptible isolates compared with clinical breakpoints. Study 3 was a factorial survey to assess the factors that influence veterinarians' decisions to prescribe antimicrobials to sheep and beef farmers. The main finding was that confidence in the farmer's judgement of disease had the largest influence on the veterinarians' decision to prescribe. The final four studies investigated farmers' decision-making around antimicrobials. Study 4 was a survey of beef farmers in England and Wales. The key conclusion was that although self-reported antimicrobial use appeared to be low, some gaps in farmers' knowledge around antimicrobial use were identified. Study 5 was a survey of sheep farmers in the UK. The important findings were that farmers' who carried out traditional practices and did not carry out modern practices were more likely to have attitudes towards antimicrobials that do not align with current recommendations. Study 6 used a mixed-methods approach to understand why farmers use, or do not use, prophylactic antimicrobials to prevent neonatal lamb diseases. Key findings were that oral antimicrobials were dissociated from parenteral antimicrobials and farmers perceived that control of neonatal disease was due to luck or chance. Farmers who used antimicrobials for treatment of disease were influenced by social pressures; whereas, farmers who routinely used prophylactic antimicrobials did so due to anticipated regret and experiential avoidance. Study 7 used qualitative interviews to understand sheep and beef farmers' perceptions of risk around antimicrobial use and resistance. The main findings were that respondents reported not having the technical knowledge and skills needed to measure antimicrobial use and resistance and were concerned that reducing their antimicrobial use would have negative consequences. Farmers put the responsibility for managing antimicrobial use on their veterinarian and blamed other farmers for antimicrobial resistance. Across the studies, the importance of recording and interpreting data was highlighted as a common theme. Common factors which influenced farmers' decision-making were also identified including: identity, experience, social norms, capability, responsibility and emotion. Further research should seek to incorporate these decision-making factors into behaviour-change interventions to improve farmers' antimicrobial use behaviours. The findings of this research have important industry and policy implications in terms of how antimicrobial use targets are set and how antimicrobial use and resistance should be measured on sheep and beef farms