AimsThe aims of this work were to develop a model of dairy farm waste milk and to investigate methods for the bioremediation of milk containing cefquinome residues. Methods and ResultsUnpasteurized milk and UHT milk that had both been spiked with cefquinome at a concentration of 2gml(-1) were used as a model for waste milk containing cephalosporin residues. Adjustment of the spiked UHT milk to pH 10 or treatment with conditioned medium from bacterial growth producing cefotaximase, were the most effective methods for decreasing the cefquinome concentrations within 24h. A large-scale experiment (10l of cefquinome-spiked unpasteurized milk) suggested that fermentation for 22h at 37 degrees C followed by heating at 60 degrees C for 2h was sufficient to decrease cefquinome concentrations to below the limit of quantification (<125gkg(-1)) and to kill the majority of the enriched bacterial population. ConclusionsOne or a combination of the bioremediation methods described may have potential as a practical treatment for dairy farm waste milk. Significance and Impact of the StudyTreatment of waste milk to decrease cephalosporin residue concentrations and also to kill bacteria prior to feeding to dairy calves could decrease the risk of selection for ESBL bacteria on dairy farms.