National Office of Animal Health
...for the welfare of all animals

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Topics and Briefing Documents

General Overview
Growth promoters












Antibiotics for Animals
An Overview

Healthy animals mean healthy food. Animals, just like humans, can suffer from disease. NOAH believes it would be a rejection of responsibility towards the production of healthy food to deny animals access to medicines which help to keep them healthy. Animals, like people, need antibiotics too.


The term antimicrobial describes a medicine which destroys or inhibits the growth of bacteria. Most are naturally produced by bacteria and fungi, others are man-made but have the same effect. “Antibiotic” is popularly used to describe this whole range of chemicals. Strictly, it should only apply to the naturally derived chemical substances, with the term antimicrobial describing the bigger group: however, we will use the popular terminology here.


The introduction of antibiotics has saved countless lives. Without antibiotics, pet and farm animals could endure pain and suffering when ill and the safe production of food could be endangered. This position paper addresses four issues facing the UK animal health industry:

  • The correct use of antibiotics in the treatment of sick animals.
  • The appropriate use of antibiotics to ensure animals do not develop illness.
  • The beneficial use of antibiotics in animal production.
  • Resistance to antibiotics.

It concludes: animals need antibiotics, too

Licensed Products

Like human medicines, by law all animal medicines require official marketing authorisations before they can be marketed. Authorisation is given only when data collected over many years’ research are approved by independent UK and European scientific and technical experts. These data include full dossiers on quality, effectiveness and safety for animals and especially safety for users, consumers, and for the environment.

Of special importance is the evaluation and operation of withdrawal periods - the time during which treated animals cannot be slaughtered for food, nor can their products enter the human food chain. Extensive testing by highly sensitive methods and enforcement of the required withdrawal period by vets and farmers ensures safety of food from such animals1.

Usage in animals

The continued responsible use of antibiotics has given man and animals freedom from many diseases and safe and efficient food production on farms. It is important to recognise that antibiotics cover a very wide range of compounds, split into many different classes.

In animal medicine, antibiotics are used in two main ways: to treat individual sick animals or to treat a group of animals that have been in close contact with sick animals, some of which may be incubating the disease, to prevent the disease from spreading within the herd/flock.

To Treat Disease

Like humans, when animals fall ill, they may need medicines and courses of antibiotics are prescribed when necessary. These antibiotics are available only with a veterinary prescription and it is the veterinary surgeon who decides what to administer and when to use them. For example antibiotics may be given in different ways, such as by tablet, by injection, in drinking water or in food and their prescription will be for as short a period as necessary to beat the disease.

Without antibiotics, if they contract a bacterial disease their condition can deteriorate rapidly, resulting in suffering and, potentially, death. Disease can also spread to other animals and in the case of zoonoses, people can be affected.

Where livestock are grouped together, it is often necessary to treat the whole group when only a few are showing signs of illness. This is because others in the group may already be incubating the disease following close contact with the affected individuals.

To Prevent Disease

Prevention is always better than cure, particularly in flocks and herds where disease can spread rapidly.

To prevent outbreaks of infectious bacterial disease when animals are most at risk, and animals are known to be susceptible, courses of appropriate antibiotics may be prescribed by a veterinary surgeon.

Resistance to Antibiotics?

Not all antibiotics work against all bacteria. It is important to choose the right one and to follow the tried and tested correct dosage levels and treatment recommendations.

Concerns that antibiotics may be losing their effectiveness are not new.

Resistance to antibiotics is seen most commonly in hospitals where antibiotic usage is high and where the ‘selection pressure’ creating and maintaining a pool of resistant bacteria is also high. Many antibiotics have been in animal use for 50 years and resistance here is not seen as a significant problem.

There is currently concern in some quarters that use of antibiotics in animals may compromise the effectiveness of related medicines in man. The animal health industry recognises these concerns and takes seriously its own responsibility in this area. As a result, extensive studies, set up in conjunction with the relevant regulatory authorities, are underway to help shed more light on this subject. Industry is also heavily involved, from a worldwide to a UK level, in the development of responsible use guidelines. In the UK these are produced by RUMA (the Responsible Use of Medicines in Agriculture Alliance).

This type of work is not new: for decades, investigations in many countries, and different species, have been conducted and no conclusive evidence produced. There have been multiple resistant Salmonellae in Europe for 30 or more years. In the 1980s, high incidence of Salmonella Typhimurium DT204C was a major concern; that disappeared over time. More recently, Salmonella Typhimurium DT104 has been the issue, but that is now on the decline. So the situation is certainly not static as far as food poisoning bacteria are concerned and is often unrelated to medicines used in farming.

For example, in 1999, the UK's Advisory Committee on the Microbiological Safety of Food (ACMSF) published its report recommending 'evolution not revolution', with proposals in line with the existing responsible use initiatives.

And in 2003, the UK’s Veterinary Products Committee published a report on antimicrobial resistance. It announced it stressing: “Antimicrobials are essential drugs for the treatment and prevention of disease. They help reduce animal suffering and contribute to the production of healthy food.

In 2004, an international group of leading independent scientists, headed by Professor Ian Phillips, published a critical review of the all the research and information relating to the question “Does the use of antibiotics in food animals pose a risk to human health?” In all, some 276 references were cited in the review. Their main conclusions were: “All the facts at our disposal persuade us that whereas resistance is undoubtedly selected in man and animals by the use of antibiotics, in organisms that are part of the normal flora as well as in pathogens, including zoonotic pathogens, and whereas some resistant organisms can be shown to reach man via the food chain, little additional harm results from resistance, even when infection supervenes. Only in the case of salmonellae and campylobacters do risk analyses, albeit still hampered by a lack of data, suggest that resistance possibly acquired in animals may add, albeit very little, to the burden of human disease.” (Ref: I Phillips et al (2004), Journal of Antimicrobial Chemotherapy 53, 28–520)

These conclusions were endorsed by Prof Phillips’ 2007 paper “Withdrawal of growth-promoting antibiotics in Europe and its effect in relation to human health.” (Ref: I Phillips (2007), International Journal of Antimicrobial Agents 30, (2007) 101-107)

(For more information see NOAH briefing document No 11 Antibiotic Resistance).


  • Antibiotics are essential for animal health and welfare.

  • All antibiotics used in animals are thoroughly tested and independently assessed prior to their approval for use.

  • Farmers and their veterinary surgeons have responsibility and a legal obligation to observe post-treatment withdrawal periods to avoid residues in the final food.

  • All groups involved in food production have agreed common “Responsible use policies” for all medicines, including antibiotics. An example of this is the guidelines produced by RUMA on responsible use of antimicrobials in the major farm species.

  • The concerns about potential impact on human health continue to be addressed by industry and independent bodies.

  • There is a remarkable lack of documented evidence that use of antibiotics in livestock has been proved to cause treatment failure in people.

  • Antibiotics must remain available for animal usage to help maintain animal health and welfare

Reviewed June 2010

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1 NOAH publishes a comprehensive listing of manufacturers' recommended and approved withdrawal periods in the Compendium of Data Sheets for Animal Medicines.




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