Elucidating bacterial antimicrobial resistance in dairy calves and the surrounding farm environment.. Elucidating bacterial antimicrobial resistance in dairy calves and the surrounding farm environment.

The consumer demand for bovine dairy and meat products in several countries is constant, whilst in some global locations an emerging market is rising. To meet the demands of these consumer markets, cow-rearing farmers have to balance the demand for high protein to yield a profit and maintenance of healthy animals from calf to adult. Despite good animal management procedures animals often suffer at some point during their life time from a microbial infection that often require treatment with antimicrobial drugs e.g., antibiotics or antifungals. Within in dairy farms the most common illness that requires veterinary antibiotic drugs is mastitis. Animals that undergo this treatment are required to go through a withdrawal milking period where any produced milk cannot be delivered to commercial dairies for human consumption. Often milk from animals in a withdrawal milk period is fed to calves to reduce farming costs or is discarded into drains, watercourses or discarded on manure heaps. This can exacerbate two problems on dairy farms, the first is that this could influence the fed calf’s microbiome and promote fecal shedding of antimicrobial resistant (AMR) bacteria such as Escherichia coli and the second is antibiotic drug residue that could enhance antimicrobial resistant bacterial strains within the farm environment. An important consideration that should be taken in account is that antibiotic drugs used in food producing animals and in human medicine often belong to the same or belong to the same antibiotic drug classes. Therefore, any generated AMR bacteria could impact any mammalian host or by horizontal gene transfer mechanisms could disseminate their acquired antibiotic resistance genes (ARGs) or plasmids to a large variety of bacterial species in the vicinity.