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New study assesses antimicrobial use, views in food-producing animals

Study shows difficulty involved in monitoring and regulating antimicrobial use in animal ag.

A new study led by academics at the Bristol Veterinary School in the U.K. has reviewed the literature on the use of antimicrobials in livestock practice together with the views of stakeholders.

The study found that although there are some barriers to change, there is a clear awareness of the issue among the livestock sectors and a willingness to modify antimicrobial use.

Food-producing animals throughout the world are likely to receive antimicrobials when needed to treat infections. There are concerns, however, that antimicrobial use in human and veterinary medicine is causing antimicrobial resistance (AMR) in both humans and animals.

The Rapid Evidence Assessment (REA), led by professor Henry Buller at the University of Exeter and Dr. Kristen Reyher at the University of Bristol, investigated what is currently known about the use of antimicrobials in food-producing animals, the practices and views of the stakeholders involved in the administration of antimicrobials and the availability and validity of data on antimicrobial use in practice.

They identified and reviewed 48 papers published in peer-reviewed journals between 2000 and 2016. Key drivers of change in antimicrobial use in food-producing animals, along with barriers to change, were identified, indicating the multitude of issues surrounding current knowledge of antimicrobial use and attitudes about the reduction of antimicrobial use in livestock, Buller and Reyher said.

The study identified a difference between and within countries, production types and individual farms that showed the difficulty of the challenge involved in monitoring and regulating antimicrobial use in animal agriculture. Many factors that could influence the frequency of AMR in livestock are of concern across all sectors of the livestock industry, including inflexibility in production systems, low capacity for re-investment in farm buildings and high production costs, all of which are barriers to reducing antimicrobial use, the researchers said.

Reyher, senior lecturer in farm animal science at the Bristol Veterinary School, said, “The REA highlights the potential role not only of farmers and veterinarians but also of other advisers, public pressures and legislation to influence change in the use of antimicrobials in livestock and to improve the system of farming for the benefit of all animals and humanity.”

A number of positive drivers towards reduced antimicrobial use were also identified, including new methods of knowledge exchange and learning to improve awareness of responsible antimicrobial use, higher levels of on-farm biosecurity, better and wider use of diagnostics and wider use of vaccines, Buller and Reyher said.

Evidence that farmers recognize and acknowledge the need to reduce antimicrobials was identified, although no evidence that medicine sales by veterinarians drives overuse of antimicrobials was found.

The researchers noted that many factors that could influence the prevalence of AMR in livestock species remain a concern, including the improper use of antimicrobials in both the pig and cattle sectors across all global regions. Prophylactic and metaphylactic use of antimicrobials has been identified to historically be common practice across all sectors for which relevant literature was found, although this is changing in many areas of the world.

The study found that there was a lack of literature about the use of antimicrobials in poultry production, especially within the European Union. It is possible that data on antimicrobial use in poultry are collected by poultry producers in some countries but are not available in the published literature, Buller and Reyher said. The researchers suggested that work should be done to combine and publish any existing data or investigate this area of antimicrobial use further.

Levels of farmer knowledge about the prudent use of antimicrobials varied among groups, and veterinary input — although respected — was low in some geographical locations.

The study found that economic concerns and restrictions relating to farm infrastructure or production type could limit farmers’ ability or motivation to alter antimicrobial use in their animals. Veterinary advice, public pressures, input from other advisers and moral obligation also influence farmers’ attitudes on use of antimicrobials, the researchers said.

Similarly, veterinarians' prescribing habits have been shown to be influenced by similar factors to differing degrees, and veterinarians’ confidence in their own knowledge of the products they are prescribing also influence prescribing behavior, according to Buller and Reyher.

The researchers believe that increasing knowledge of how to use antimicrobials properly as well as raising awareness of AMR and encouraging a reduction in antimicrobial use in these sectors is essential, and addressing responsible use across groups could have a greater effect than targeting specific groups individually.

The paper, "Antimicrobial Use in Food-Producing Animals: A Rapid Evidence Assessment of Stakeholder Practices & Beliefs," by Hockenhull et al. was published in Veterinary Record.

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