Alternatives to antibiotics for bovine mastitis management: a systematic review and meta-analysis of efficacy and translational evidence.

The impact of antimicrobial resistance (AMR) on diary production and global food security due to bovine mastitis raises the need to develop new alternatives to reduce reliance on antibiotics. While an increasing number of alternatives are being evaluated, a comprehensive quantitative synthesis of their potential is scarce. We conducted a systematic review and meta-analysis following PRISMA guidelines to evaluate antimicrobial potency and translational relevance of the current alternatives. Relevant studies, published between January 2020 and June 2025, were identified and screened for eligibility. Quantitative outcome data were analysed using a multilevel random-effects model and meta-regression. All statistical analyses were performed using R software. Sixty eligible studies, spanning 28 countries and 11 intervention types, were included. Among other alternatives, phytochemicals and nanoparticles were most extensively evaluated, with overall dominance of in vitro experiments. Based on the minimum inhibitory concentration (log10 MIC) data, the overall pooled estimate of the alternatives was 2.83µg/ml (95% CI: 2.36-3.30) for Staphylococcus aureus, and 2.89µg/ml (95% CI: 2.27-3.51) for Escherichia coli. Substantial between-study heterogeneity (τ² > 0.8, I² > 95%, p < 0.0001) and a wide prediction interval (0.45-5.21µg/ml) were observed. Meta-regression analysis indicated significantly higher antimicrobial potency in nanoparticles than phytochemicals against Staphylococcus aureus, with lower log10 MIC values (β = -0.131, p < 0.0001). In conclusion, prioritising harmonised research methodologies and robust in vivo validation of the most promising alternatives are needed before emerging alternatives can contribute meaningfully to sustainable mastitis management and AMR mitigation.