Antibiotic residues in farm fertilizers from conventional pig husbandry

Conventional pig husbandry at large-scale farms is inevitably linked to frequent applications of antibiotics for therapeutic use, possibly resulting in the contamination of farm fertilizers by antibiotic residues and the simultaneous occurrence of antibiotic resistance genes and mobile genetic elements. This study, therefore, aimed to link for the first time the findings of antibiotic residues in farm fertilizers with the corresponding antibiotic application patterns, therapy frequencies and number of treated pigs at 8 pig fattening and 8 pig breeding farms with conventional manure management and 5 pig breeding farms with farm-own biogas plants as well as 4 corporate biogas plants in Lower Saxony, Germany. In addition to the farm-scale monitoring activities, laboratory simulation tests on manure treatment technologies practiced today, i. e., manure storage, anaerobic digestion in biogas plants without/with manure separation, digestate storage and digestate drying, applying doxycycline as the main test substance were performed to evaluate the findings at farm and biogas plant scale and to check for mitigation strategies.