Do antimicrobial mass medications work? A systematic review and meta-analysis of randomised clinical trials investigating antimicrobial prophylaxis or metaphylaxis against naturally occurring bovine respiratory disease

Summary

This systematic review and meta-analysis synthesised 58 publications encompassing 169 RCTs spanning 50 years to evaluate antimicrobial prophylaxis and metaphylaxis against naturally occurring bovine respiratory disease. Whilst these interventions demonstrated moderate relative risk reductions in BRD morbidity, effects were highly variable and dependent on antimicrobial class, intervention type, baseline disease rates, and trial duration. The authors conclude that despite widespread use, the underlying drivers of BRD in intensive cattle production are more likely related to industry infrastructure than infectious disease biology alone, suggesting a need to reconsider current prophylactic and metaphylactic antimicrobial use strategies.

Regional applicability

The findings are globally relevant given the worldwide reliance on antimicrobial mass medication in intensive cattle production, including the United Kingdom. The review's conclusions regarding infrastructure-related disease risk and variable efficacy across antimicrobial classes are directly applicable to UK feedlot and veal calf production systems, and support arguments for structural and management-based disease prevention alternatives.

Key measures

Relative risk reduction in bovine respiratory disease morbidity and mortality; absolute risk reduction; stratification by antimicrobial class, metaphylaxis definition, BRD attack rates, and trial duration

Outcomes reported

The meta-analysis evaluated the effectiveness of antimicrobial prophylaxis and metaphylaxis in reducing morbidity and mortality from naturally occurring bovine respiratory disease across 169 randomised controlled trials. It assessed relative risk reductions and their variability by antimicrobial class, intervention type, and trial characteristics.

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