From the application of antibiotics to antibiotic residues in liquid manures and digestates: A screening study in one European center of conventional pig husbandry

In conventional pig husbandry, antibiotics are frequently applied. Together with excreta, antibiotic residues enter liquid manures finally used as organic soil fertilizers or input materials for biogas plants. Therefore, this first screening study was performed to survey the application patterns of antibiotics from fall 2011 until spring 2013. Manures and digestates were then analyzed for selected antibiotic residues from spring 2012 to 2013. The data analysis of veterinary drug application documents revealed the use of 34 different antibiotics belonging to 11 substance classes at 21 farms under study. Antibiotics, particularly tetracyclines, frequently administered to larger pig groups were detected in manure samples up to higher mg kg−1 dry weight (DW) concentrations. Antibiotic residues in digestates, furthermore, show that a full removal capacity cannot be guaranteed through the anaerobic digestion process in biogas plants.