Assessment of Antimicrobial Resistance in Dairy Herds: A Case Study of Green Valley Dairy Farm

Thesis Abstract

The widespread use of antimicrobials in dairy farming has raised significant concerns regarding the emergence and proliferation of antimicrobial resistance (AMR), which poses a serious threat to both animal and public health. This study aims to assess the prevalence and determinants of antimicrobial resistance in the bacterial flora of dairy herds at Green Valley Dairy Farm, with a specific focus on identifying resistance patterns, contributing factors, and potential transmission pathways. The research adopts a cross-sectional case study design, integrating microbiological, molecular, and statistical analyses to generate comprehensive insights into AMR dynamics within the farm environment. The study population comprises all lactating dairy cows and associated environmental samples (n=150 cows and 50 environmental swabs) from Green Valley Dairy Farm, selected through stratified random sampling to ensure representation across different herd sections. Data collection involved structured interviews with farm personnel to document antimicrobial usage (AMU) practices, farm management routines, and health records, complemented by the collection of milk and fecal samples from selected animals and environmental samples from milking parlors, water sources, and bedding areas. Microbiological isolates, primarily Escherichia coli and Staphylococcus aureus, were obtained through standard culture methods, and antimicrobial susceptibility testing was conducted using the Kirby-Bauer disk diffusion technique aligned with Clinical and Laboratory Standards Institute (CLSI) guidelines. Molecular analysis involved PCR detection of resistance genes, including blaCTX-M and mecA, to elucidate genetic determinants of resistance. Quantitative data were analyzed using descriptive statistics to determine the prevalence of resistant isolates, with inferential analysis employing logistic regression models to identify significant predictors of AMR, such as antimicrobial prescription patterns, farmer knowledge, and hygiene practices. Data integration aimed to establish associations between antimicrobial usage metrics and resistance profiles. The study hypothesizes that inappropriate antimicrobial use, combined with suboptimal farm hygiene, significantly contributes to AMR prevalence within the dairy herd. Expected findings include a high prevalence of resistance to commonly used antibiotics such as tetracyclines, sulfonamides, and beta-lactams, with detection of critical resistance genes implicating horizontal gene transfer mechanisms. The data are anticipated to reveal significant correlations between antimicrobial usage patterns and resistance profiles, supporting the hypothesis that misuse and overuse of antimicrobials exacerbate resistance development. These findings are expected to contribute to a deeper understanding of AMR epidemiology in dairy production systems, emphasizing the need for targeted antimicrobial stewardship, improved farm hygiene, and policy interventions. This research makes a substantial contribution to knowledge by providing empirical evidence on the prevalence and drivers of AMR in a typical dairy farm setting within the region, addressing a critical gap in local data on antimicrobial usage and resistance dissemination. The study underscores the importance of adopting an integrated One Health approach by linking farm-level practices with broader public health concerns. Main conclusions indicate that strategic interventions, including farmer education, judicious antimicrobial prescribing, and enhanced biosecurity measures, are essential to curbing the rise of AMR in dairy herds. Based on the findings, recommendations include developing farm-specific antimicrobial stewardship programs, implementing routine resistance monitoring, and strengthening regulatory frameworks governing antimicrobial use in livestock. Future research should focus on longitudinal surveillance and the effectiveness of intervention strategies, as well as exploring broader environmental reservoirs of resistance genes. Overall, this study provides a critical evidence base to inform policy, improve farm management practices, and safeguard the efficacy of antimicrobials in veterinary medicine.