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Antimicrobial Reduction in pork production

Consumers, food and restaurant companies, WHO and various governments are requiring livestock farmers to produce meat raised with lower use of antimicrobial drugs.  The discussion has moved on from analysing the potential risks that the use of antimicrobials in livestock can have on society to managing the new situation were pork producers will have to raise pigs using less, or even without, antibiotics.  This is of course at the same time as a predicted increase in demand for protein, unprecedented restrictions on land and water use and rising input costs. What should producers do?

Antibiotic resistance is a global public health problem. While antibiotic resistance exists in nature, even in places where antibiotics have never been used, it also is clear that when bacteria are exposed to an antibiotic; some surviving strains are selected leading to the development of antibiotic resistant populations. Any use of antimicrobials in human and veterinary medicine could result in the development of antimicrobial resistance. In addition, the possible zoonotic transfer of resistant bacteria or genes is nowadays the focus of the intense public and scientific debate. The risk of antimicrobial resistance increases if antimicrobials are used inappropriately.

The World Organisation for Animal Health (OIE) and the European Commission (EC) as well as the WHO have proposed strategies to tackle the issue of antimicrobial resistance. The strategies can be summarised in the four headings:

1. Good governance and usage principles for antibiotics.

Typically the legal requirements for use of medicines in pigs are determined by Government regulations or voluntary industry guidelines and principles of use.  The global tendency is towards removing the use of antibiotics for growth promotion. Pork producers can lobby governments for reasonable legislation, but need to be aware that the weight of public opinion is towards reduction in antibiotic usage.

2. Monitoring of antimicrobial usage and resistance.

This has historically been information collected by government bodies and public health departments. A successful system that monitors the development of resistance in humans and animals together with data on antibiotic usage that has been in place for over 20 years is DANMAP (Use of antimicrobial agents and occurrence of antimicrobial resistance in bacteria from food animals, food and humans in Denmark).  Many countries have systems to collect broad antimicrobial use in animals (Kg of active ingredient sold per year) but what is more difficult is to collect and track antimicrobial use based on species, weight or age of animals to allow for benchmarking. Pork producers can also be proactive and collect their own antimicrobial use data.

3. Unspecific prevention

These are interventions at the production level that reduce the risks of diseases developing on the farm.  They include a broad range of measures, from providing good housing and management to reduce environmental challenges and stress, correct nutrition and diets to biosecurity.  This is an area of direct responsibility for Pork producers and Veterinarians.

4. Specific prevention.

These are disease or pathogen specific interventions that will result in elimination or reduction of the disease and therefore avoid the need for antibiotics. This could be focused on control of primary bacterial infections or control of viral diseases that can trigger more severe clinical outcomes. Veterinarians and the farms they oversee have a direct impact on implementation of prevention programmes that will reduce the reliance on antibiotics.

WHY MEASURE ANTIBIOTIC CONSUMPTION? You cannot manage what you do not measure

The purposes of measuring antibiotic consumption are:

  1. To monitor antimicrobial use trends over time

  2. To compare consumption between countries or species (humans, livestock, pets)

  3. For benchmarking, between different systems measured the same way. Which has been used mostly to highlight “excessive” users in hospitals or farms (for example the yellow card system in Denmark)

  4. To measure associations between usage of antimicrobials and development of resistance

    Monitoring the usage of antibiotics has been complicated by many factors including; variation in the data collected, no agreed standards or methodology for computing the usage, difficulty benchmarking across countries, species and systems of production and concerns about overregulation. Initiatives to monitor antimicrobial usage in livestock can be imposed by government regulation or proactively implemented by quality assurance schemes or production companies. While reports have described serious misuse of antibiotics and the need for rational antibiotic prescribing practices in livestock, there are surprisingly few descriptions or comparisons of antibiotic consumption until very recently. Since 2009 ESVAC (European Surveillance of Veterinary Antimicrobial Consumption) has been collecting usage in the EU.  In their most recent report they highlight some of the difficulties collecting and comparing the data from different countries while indicating that there is large variation between countries and that overall the use of antimicrobials in animals has been following a downward trend. This lack of credible information has blocked discussions about acceptable or reasonable levels of consumption in pork production.

    Many factors must be considered when trying to define ideal levels of antimicrobial use, including disease prevalence, antibiotic susceptibility patterns, antibiotic prescribing practices and legislation and finally farmer and Veterinarian behaviour patterns. Comparisons between populations or pig production systems raised under similar conditions can give more constructive answers and guidance to producers. Until consistent comparable measurements of consumption are routinely available to farmers, Veterinarians in clinical practice, researchers and policy-makers, it will be difficult to quantify and resolve this growing challenge.

To allow for credible data comparison, ESVAC has suggested the use of two standardized units of measurement:

Defined Daily Dose Animal (DDDA or DDDvet): This is an adaptation of the DDD used in human medicine, “the assumed average maintenance dose per day for a drug used for its main indications in adults”. Various countries use variations of this, for example DADD (Denmark), ADDkg or daily dosages dd (Netherlands). These measurements are all reported in mg/kg/day, but how the number is computed varies. Some calculate the dosage of an antimicrobial based on average dose on the label, others the median or even maximum labelled dose.  How these are reported also changes (by species, by product class, or even age group).

Defined Course Dose Animal (DCDA): This is a technical unit of measurement usually based on recommendations as described in antimicrobial product information and in some cases on information from experiments or scientific literature.

ESVAC has been compiling a common standardized list of DDDvet for livestock species from all EU countries.

Not all uses of antibiotics will result in the same risk of developing resistance- Prudent use of antibiotics

International, national, and local antibiotic stewardship guidelines have been developed to encourage prudent use and to limit unnecessary exposure to antibiotics, with the ultimate goal of preserving their effectiveness.

What is a PRUDENT USE of antibiotics?

Prudent use of antimicrobials, which is also referred to as “responsible use” or “antimicrobial stewardship”, is the optimal selection of drug, dose and duration of antimicrobial treatment, along with reduction of misuse or excessive use as a means of slowing the emergence of antimicrobial resistance (Shales et al., 1997).

What are the objectives of Prudent Use Principles?

Prudent use of antibiotics aims to promote a more rational and targeted use, thereby maximising the therapeutic effect and minimising the development of antimicrobials resistance. Prudent use of antibiotics should predominantly target overall reduction of consumption, limiting their use to situations where they are necessary. In these situations antibiotics should be used as targeted treatment and according to best practices.

Strategies to reduce reliance on antibiotics

As we saw earlier there are two primary interventions to reduce antimicrobial use in pork production, non-specific or general prevention and specific prevention targeted at particular diseases or infections. The advice from a specialist swine Veterinarian and relying on an expert team of advisors on housing, nutrition and genetics plays a central role in the successful reduction in antimicrobial use. There are 4 main steps required:

Diagnosis: Specialist veterinarians will start with a deep understanding of the disease situation on the farm and can collect samples and carry out testing to determine the cause of an infection or disease on the farm. Often we are dealing in multifactorial diseases and need to consider the whole farm in our analysis (infection chain).  At this stage if a bacterial cause has been found the laboratory can carry out tests for the most appropriate antimicrobial treatment (antibiotic susceptibility testing). For each bacteria or antibiotic this can be reported as susceptible, intermediate or resistant. More accurate still is to determine the MIC (Minimum Inhibitory concentration) the lowest concentration of an antimicrobial that will inhibit the growth of that bacteria.

Advice on control : Once the complete picture is understood the interventions can be implemented.

Specific interventions, for example a curative treatment with an antibiotic using prudent use principles to stop the disease and reduce suffering and mortality. Critically this must be followed by specific control of both bacterial and viral infections using high quality reliable vaccines.  The Vet is ideally placed to advise farmers on the correct timing of vaccines to maximise efficacy. Again it is essential to control all sections of the production chain (Prevention Chain).This will result in maximum immunity to the diseases that affect the farm.  It has been demonstrated that usage of appropriate vaccinations can result in less antibiotic use on the farm.

General interventions are often as important;  We need to minimize exposure to pathogens. This can be achieved with internal biosecurity, ventilation and hygiene to reduce presence, load and spread of pathogens.  All in all out management, good washing and disinfectant processes are critical in all farms.  Good external biosecurity will avoid new pathogens entering our productions system.

Recent work measured the levels of implementation of biosecurity measures in pig production in four EU countries (Postma et al 2016). The study also examined possible associations between the biosecurity compliance and farm and production characteristics.  They conclude that there is room for improvement in biosecurity. The paper has shown that improved biosecurity and management practices focused on prevention could lead to a reduction in antimicrobial use, better overall health status and higher animal production and welfare. Prevention is better than cure!

Reducing stress particularly at the time of weaning by increasing the weaning age and optimal nutrition are also beneficial, particularly to reduce the need for antimicrobials to control post weaning diarrhoea.

Monitor outcomes; by routine and periodic follow up and revision of disease control plans a Veterinarian can optimize the preventative plan.  By monitoring treatment outcomes and antibiotic susceptibility results the Vet can update the advice on the best antibiotic treatment.

Educate, finally it is essential for pork producers to be informed of the best practices and understand legislation and public health developments that impact their business.

Reduction in the use of antibiotics does not always equate to reduced performance or increased costs of production

Herd-level interventions are needed to achieve national and European antibiotic reduction targets.  Recent surveys carried out with pig farmers and Vets found that many intervention to reduce antibiotic use were relatively easy to implement and had a high likelihood of success (Postma et al 2015).  The experts found that the top 5 measures in perceived return on investment were: Improved internal biosecurity, use of zinc/metals, implementation of a diagnostic/action plan, feed quality/optimization and Climate/environment modifications.  Veterinarians ranked internal biosecurity and implementation of vaccinations as the most valuable interventions to reduce antibiotic use.

Alternative preventive measures are not well understood in terms of the feasibility, effectiveness and return on investment. The objective of a recent study was to assess for one year, across 70 farrow-to-finish pig farms located in Belgium, France, Germany and Sweden, the technical and economic impact of herd-specific interventions aimed at reducing antimicrobial usage in pig production (Colineau et al 2017). Herd-specific interventions were defined by the farmer and the herd veterinarian and compared before and after the intervention. Following interventions, a substantial reduction in antimicrobial use was achieved without negative impacting overall farm technical performance. Better compliance with the plan resulted in better reduction in antibiotics. A median reduction of 47% of the treatment incidence from birth to slaughter was achieved. This represented over 30% median reduction of antimicrobial expending. Mortality in suckling piglets, weaners and fatteners, daily weight gain and feed conversion ratio did not significantly change over the course of the study.  On the other hand, the number of weaned piglets per sow per year slightly increased.

Pork producers, their Vets and advisors should take the challenge of antimicrobial use reduction as an opportunity to optimise production and disease prevention tactics for sustained productivity and improved animal health and welfare.

Take home messages

  1. Producing pork with fewer antibiotics is a growing requirement from consumers and governments.

  2. You cannot manage what you don’t measure. Pork producers and Vets need to developed practical systems to monitor antimicrobial use on their farms

  3. The role of the herd Veterinarian is crucial in developing specific and general disease prevention strategies which lead to reduce usage of antimicrobials

  4. Reducing dependence of antimicrobials in your production system does not automatically mean an increase in the cost of production


References and links

  1. http://www.danmap.org/~/media/Projekt%20sites/Danmap/DANMAP%20reports/DANMAP%20%202015/DANMAP%202015.ashx
  2. European Medicines Agency (2015). Sales of veterinary antimicrobial agents in 26 EU/EEA countries in 2013. 5TH ESVAC report
  3. http://www.ema.europa.eu/docs/en_GB/document_library/Report/2015/10/WC500195687.pdf
  4. Grave K, Torren-Edo J, Mackay D. Comparison of the sales of veterinary antibacterial agents between 10 European countries. J Antimicrob Chemother. 2010;65(9):2037-2040.
  5. Postma, M. et al (2014) Assigning defined daily doses animal: a European multi-country experience for antimicrobial products authorized for usage in pigs. The Journal of Antimicrobial Chemotherapy, 1–9
  6. Collineau L. et al (2017) Guidance on the selection of appropriate indicators for quantification of antimicrobial usage in humans and animals. Zoonosis and Public Health 64: 165-184
  7. World Organisation for Animal Health (OIE) (2003). – OIE International Standards on Antimicrobial Resistance. Available at: www.oie.int/doc/ged/D9769.pdf.
  8. FDA CVM (2012). - GFI #209 The Judicious Use of Medically Important Antimicrobial Drugs in Food-Producing Animals.
  9. https://www.fda.gov/downloads/AnimalVeterinary/GuidanceComplianceEnforcement/GuidanceforIndustry/UCM216936.pdf
  10. Official Journal of the European Union (2015). Commission notice: Guidelines for the prudent use of antimicrobials in veterinary medicine (2015/C 299/04). Official Journal of the European Union of 11.9.2015. http://ec.europa.eu/health//sites/health/files/antimicrobial_resistance/docs/2015_prudent_use_guidelines_en.pdf
  11. Minapig consortium project:https://www.era-learn.eu/network-information/networks/emida/2nd-emida-joint-call-on-emerging-and-major/evaluation-of-alternative-strategies-for-raising-pigs-with-minimal-antimicrobial-usage-opportunities-and-constraints
  12. Postma M.,. Backhans A, Collineau L., S. Loesken, M. Sjölund, C. Belloc, U. Emanuelson, E. Grosse Beilage, K. D. C. Stärk and J. Dewulf  (2016). The biosecurity status and its associations with production and management characteristics in farrow-to-finish pig herds.
  13. Animal (2016), 10:3, pp 478–489
  14. L. Collineau ,∗, C. Rojo-Gimeno, A. Léger, A. Backhans, S. Loesken, E.Okholm Nielsen, M. Postma, U. Emanuelson, E.grosse Beilage, M. Sjölun,E. Wauters, K.D.C Stärk, J. Dewulf, C. Belloc, S. Krebsba (2017). Herd-specific interventions to reduce antimicrobial usage in pig production without jeopardising technical and economic performance. Preventive Veterinary Medicine 144 (2017) 167–178 [accessed Jul 10, 2017].