In this study, we examined the milk microbiome in cattle immediately after lactation and at calving in the presence of differing drying-off procedures.

The widespread blanket usage of antibiotics at the end of lactation in dairy cattle is under increasing scrutiny, due to concerns about antimicrobial resistance. To lower antibiotic use in dairy farming, farmers are encouraged to use “selective dry cow therapy” whereby only cows viewed as at high risk of mastitis are administered antibiotics. However, we do not yet have an understanding of how this practice affects the udder microbiota and the knock-on effects on antimicrobial-resistant bacterial populations circulating on the farm. Here, we examine milk microbiota and antimicrobial resistance profiles at drying-off period and calving in dairy cattle under different treatment protocols. There were no significant differences in microbiota composition, bacterial load and AMR gene abundance across treatments, but significant changes were observed when comparing samples at drying-off and calving.