Effect of Sucrose Addition on Antibiotic Resistance Genes in High Moisture Alfalfa Silage
Antibiotic resistance genes(ARGs)are emerging pollutants that pose a significant threat to public health.Alfalfa silage,a high-quality,protein-rich feed for herbivorous livestock,is also identified as a potential source of ARGs in animals.This study employed metagenomic sequencing to assess the impact of sucrose addition on the overall ARGs profile in silage fermentation.Additionally,correlations between ARGs and environmental factors were investigated.The results showed that ensiling process sig-nificantly increased the overall abundance of ARGs in the silage,with tetracycline and fluoroquinolone resis-tance genes being the most prevalent types.Efflux pumps were identified as the primary resistance mecha-nism.Supplementation with sucrose during ensiling resulted in a significant reduction(P<0.05)in both the total abundance of ARGs and the abundance of tetracycline resistant gene specifically.Dominant ARGs in the silage(acrD,acrB,and mdtC)displayed a significant positive correlation(P<0.05)with the levels of acetic acid and ammonia nitrogen/total nitrogen.Pseudomonas aeruginosa and Stenotrophomonas malto-philia were identified as main bacterial hosts of ARGs in the raw alfalfa materials,whereas Escherichia coli emerged as the predominant ARG host in the silage itself.In conclusion,these findings demonstrate that sucrose addition during ensiling has the potential to mitigate the enrichment of ARGs in alfalfa silage.
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