Global impact of antimicrobial growth promoters on livestock productivity: A meta-analysis for economic modeling

The use of Antimicrobial Growth Promoters (AGPs) in livestock production is under increasing scrutiny due to concerns about Antimicrobial Resistance (AMR). However, the economic consequences of AGPs withdrawal remain insufficiently quantified, partly because globally representative estimates of their effects on productivity are lacking. This study addresses this gap through a systematic review and meta-analysis evaluating the impact of AGPs on broilers, pigs, and cattle across diverse production settings. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we screened 95 studies encompassing 128 trial observations published between 2000 and 2023, covering diverse geographic regions, income levels, and antimicrobial classes. Funnel plot analysis and Egger's test were used to detect publication bias. AGPs significantly improved Average Daily Gain (ADG) in broilers (1.78 g/day), pigs (28.15 g/day), and cattle (30 g/day); and improved Feed Conversion Ratio (FCR) in broilers (-0.05) and pigs (-0.09). Feed Efficiency (FE) in cattle also improved (0.0043). Regional differences in ADG improvement were notable in broilers. For broiler production, FCR effects varied significantly according to antimicrobial importance, with Critically Important Antimicrobials (CIAs) showing the largest effect sizes. The study revealed significant data gaps in the available scientific evidence, which limit the direct use of current findings for comprehensive economic modelling. Nevertheless, the results provide key parameters to inform the design of economic models assessing the costs and benefits of AGP withdrawal in livestock production systems.