Risks of livestock manure application

Fertilization is of vital importance to increase food production. The use of animal manure as a fertilizer poses several risks. These risks are mainly related pathogens and viruses, resistant bacteria/resistance genes and residues of veterinary medicines. The risks and adverse effects of the specific contaminants indicated, are studied.

Manure is widely used as a natural fertiliser and therefore constitutes a globally important resource for agriculture. However, manure application poses potential risks for human and animal health and may affect the ecosystem. To determine the risks involved and to be able to develop intervening measures, the fate, dissemination and the effects of antimicrobial resistant bacteria, resistance genes, veterinary medicines (among which antibiotics) and pathogens in all relevant reservoirs in the production chain and the environment must be understood. There are many different reservoirs that can contain the aforementioned contaminants, e.g. the animal, manure, soil, water and arable crops. Each of these reservoirs, the transfer from one to the other reservoir and the trade-offs among the mentioned contaminants is of relevance to understand the processes and potential health effects. As this is a comprehensive task, a multidisciplinary and multi-annual project is proposed.

In 2016, some important steps were made including drafting a priority list of antibiotics and pathogens and clarifying manure dissemination routes in The Netherlands. Furthermore, technical aspects including mechanisms of gene transfer mainly in the rhizosphere, the longitudinal effect of antibiotic residues and resistance determinants on the microbiome and resistome in faeces, and the bioactivity of antibiotic residues in manure were successfully studied. In 2017, the project will focus on obtaining additional data to be able to appoint risk levels and model the fate in the ecosystem of the prioritized antibiotics and pathogens after manure application.  Hereby special focus will be on the effect of antibiotic residues in manure on the metagenome, mobilome and virulome of crops.