Veterinary medicines and feed additives in the environment following use in the poultry industry


Veterinary medicines are a mainstay of modern farming practice and are widely used to treat disease and to protect the health of animals. However, following their use these chemicals can be inadvertently introduced into the environment where they present an ecosystem and human health risk. Veterinary medicines such as antibiotics are biologically active chemicals designed to elicit effects and this potency is not lost when these chemicals enter the environment. Antibiotics administered to poultry and livestock for example, along with feed additives, can make their way in soil systems by direct release in animal waste products. Common antibiotics used to treat bacterial infections in livestock (e.g. enrofloxacin, tetracycline or florfenicol) and feed additives such as ionophore have been reported in soils following use of manure as an organic fertiliser (Cycoń et al., 2019). This has resulted in uptake and accumulation into crops and effects on soil microbial communities (Marti et al., 2013; Carter et al., 2014). 

Therefore, before any new medicine can be brought to market it has to undergo an authorisation process which involves an environmental risk assessment. Environmental risk assessments consider the likely exposure routes, environmental fate and behaviour of the chemical. A key aspect of this assessment is evaluating the degradation potential of veterinary medicines in animal manures (Figure 1). This informs the predicted concentration of the veterinary medicine that will enter soil systems following land application of manures. It is therefore imperative that degradation assessments reflect the true complexity of environmental systems. Nevertheless, most research to date evaluating veterinary medicine degradation has focussed on liquid manures (cattle and pig) and the fate of veterinary medicines in poultry litter remains largely unknown. There is also a significant knowledge gap surrounding the fate of feed additives administered to livestock. The poultry industry continues to grow and the development of intensive production units represents a threat to the environment. Poultry manure is very different matrix to liquid manures with a lower water content and is typically aerobic. Differences in properties such as this have the potential to alter the fate and behaviour of chemicals in the manure itself and ultimately the risk of these chemicals when they are introduced into the environment.  

Figure 1 Experimental set up to investigate the fate of veterinary medicines 

This project will address this significant knowledge gap by generating new understanding around the variability and influence of properties on the degradation of veterinary medicines and feed additives. Working in collaboration with scientists at Fera Science Limited will enable access to state-of-the-art instrumentation, laboratories and specialist expertise in environmental risk assessment. Fera Science Limited has a dedicated Centre for Chemical Safety and Stewardship (CCSS) that works with a range of chemical companies focussing on the generation of experimental data to support the environmental risk assessment of chemicals used in agriculture.  CCSS comprises of ~50 scientists including environmental chemists, environmental fate scientists and ecotoxicologists with access to one of the most comprehensive analytical facilities in the UK.  CCSS routinely performs risk assessments for veterinary medicines and feed additives used in the treatment of poultry and livestock. Fera’s Plant Protection Programme contains expertise in a variety of microbiological and molecular biology disciplines, as well as a variety of different platforms that can be applied for quantifying and identifying the microbiome of a range of sample types. These include PCR, qPCR, LAMP and High Throughput Sequencing (HTS) approaches. A key aspect of this project will build on previous findings which have demonstrated that antibiotics can affect soil microbial community composition and structure to understand how manure laced with antibiotic residues can influence soil microorganisms by changing their enzyme activity and ability to metabolize different carbon sources, as well as by altering the overall microbial biomass and the relative abundance of different groups. This topic urgently warrants further investigation given the increasing use of organic fertilisers in agriculture and the demand of veterinary medicines.  

Aim and objectives 

The overall aim of this project is to better understand the fate and effects of veterinary medicines in manure-soil systems. This will be achieved using a combination of an experimental approach in the laboratory and field trials utilising facilities available at the University of Leeds farm and Fera Science Limited. The specific objectives are to: 

  1. Characterise the degradation of veterinary medicines and feed additives in poultry manure  
  2. Develop better understanding of the variability and property influence of manure type on degradation 
  3. Investigate the impact of different manure types of soil-plant interactions including impacts on soil microbial biomass and the relative abundance of different groups soil microorganisms. 
  4. Assess manure and/or soil samples for associated Antimicrobial Resistant (AMR) Bacteria or genes. This could be by; isolation of taxa or interest followed by phenotypic screening or Whole Genome Sequencing; qPCR of target AMR genes, or non-targeted High Throughput Sequencing of samples.


The successful candidate will develop a range of research skills, including experimental design, field sampling, chemical analysis, statistical analysis and data interpretation, academic writing skills and giving presentations. The successful candidate will benefit from inter-disciplinary training in analytical techniques and chemical fate and effects, as well as wider water management skills. Training will be provided in field/laboratory health and safety procedures and the use of field and analytical equipment. In addition the candidate will develop their understanding of (i) environmental pollution, in particular the impact of veterinary medicines, (ii) environmental risk assessment, and (iii) soil microbial effects. Access to facilities at Fera will Include but not limited to the efate controlled environment facility to perform and maintain degradation experiments as well as access to extensive radiolabelled and none -radiolabelled analytical chemistry facilities. The student will also have access to Fera’s Molecular Technology Unit, with the opportunity for training and analysis time on various molecular biology platforms (e.g. qPCR, HTS). 

Student profile 

We are looking for a keen interest in environmental pollution with a strong background in a physical geography, earth sciences, soil chemistry, environmental sciences or related discipline.  Strong analytical/statistical/fieldwork skills are desirable but not essential, as full training will be provided during the PhD.