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17 In pasture-based systems, changes in dairy herd habitat due to seasonality results in the 18 exposure of animals to different environmental niches. These niches contain distinct 19 microbial communities that may be transferred to raw milk, with potentially important food 20 quality and safety implications for milk producers. It is postulated that the extent to which 21 these microorganisms are transferred could be limited by the inclusion of a teat preparation 22 step prior to milking. Here high-throughput sequencing, of a variety of microbial niches on 23 the farm, is employed to study the patterns of microbial movement through the dairy 24 production chain and, in the process, investigate the impact of seasonal housing and 25 inclusion/exclusion of teat preparation regime on the raw milk microbiota from the same 26 herd over two sampling periods, i.e., indoor and outdoor. Beta diversity and network 27 analyses showed that environmental and milk microbiotas separated depending on whether 28 they were sourced from an indoor or outdoor environment. Within these respective 29 habitats, similarities between the milk microbiota and that of teat swab samples and, to a 30 lesser extent, faecal samples were apparent. Indeed, SourceTracker identified the teat 31 surface as the most significant source of contamination, with herd faeces being the next 32 most prevalent source of contamination. In milk from cows grazing outdoors, teat prep 33 significantly increased the numbers of total bacteria present. In summary, sequence-based 34 microbiota analysis identified possible sources of raw milk contamination, and highlighted 35 the influence of environment and farm management practices on the raw milk microbiota. 36