Novel characterisation of sheep flocks in Wales: A description of principal flock typologies and antimicrobial use patterns

There is increasing pressure to reduce and refine antimicrobial use (AMU) in farmed livestock, to slow the development of antimicrobial resistance (AMR) and preserve the efficacy of antimicrobials (AMs) in both humans and animals. Developing strategies to help drive the prudent use of AMs requires an understanding of the direct and indirect factors influencing the between-farm variation in AMU typically observed. Given limited evidence of risk factors in sheep, this exploratory study aimed to investigate whether sheep flocks could be classified into farm types based on farm characteristics, health parameters and management practices, and whether important differences existed in AMU between these flock types. This study was conducted on 22 sheep flocks in Wales, United Kingdom as part of a wider longitudinal study on AMU and AMR. Comprehensive surveys were administered to flocks where 147 variables regarding farm characteristics, flock health parameters and management practices were captured. AMU data for each flock were also collated. A Multiple Correspondence Analysis (MCA), followed by a Hierarchical Clustering on Principal Components (HCPC) analysis, were used to classify the flocks. The top 10 dimensions yielded by MCA explained 67.4 % of the total variance. Nine partitions of relatively homogeneous flocks, derived from three typologies produced from the first three cut-points of the HCPC dendrogram, were visualised and described. These nine partitions were characterised by 70 variable categories, principally the implementation or neglect of best-practice lameness management practices. Partitions of flocks that neglected best-practice lameness managements - characterised by delayed treatments of lame sheep, footbathing and bleeding when foot trimming - reported higher lameness prevalence and fewer lame ewes recovering within five days of treatment. These flocks had higher total AMU (mg/PCU) and used a higher mass of injectable AMs than other partitions of flocks. Flock traits, lambing practices, disease challenges and other management factors also described partitions derived in later dendrogram cuts. Findings from this study confirm good AM stewardship in sheep flocks to be a complex picture, given the typologies of flocks described and the range of factors likely to influence AMU. Opportunities for targeted strategies for sustainable reductions in AMU can be directed towards specific flock types identified, specifically within the context of lameness treatment and control. We highlight the importance of understanding flock heterogeneity, through the construction of typologies, as a means to fine-tune appropriate interventions to specific flock types in order to help drive more prudent use of AMs.