The use of antibiotics in the animal husbandry of livestock includes treatment when ill (therapeutic), treatment of a group of animals when at least one is Diagnosis with clinical infection (metaphylaxis), and preventative treatment (prophylaxis). Antibiotics are an important tool to treat animal as well as human disease, safeguard animal health and welfare, and support food safety. However, used irresponsibly, this may lead to antibiotic resistance which may impact human, animal and environmental health.
While levels of use vary dramatically from country to country, for example some Northern Europe use very low quantities to treat animals compared with humans, worldwide an estimated 73% of (mainly antibiotics) are consumed by farm animals. Furthermore, a 2015 study also estimates that global agricultural antibiotic usage will increase by 67% from 2010 to 2030, mainly from increases in use in developing BRIC countries.
Increased antibiotic use is a matter of concern as antibiotic resistance is considered to be a serious threat to human and animal welfare in the future, and growing levels of antibiotics or antibiotic-resistant bacteria in the environment could increase the numbers of drug-resistant infections in both. Bacterial diseases are a leading cause of death and a future without effective antibiotics would fundamentally change the way modern human as well as veterinary medicine is practised.
Legislation and other curbs on antibiotic use in farm animals are now being introduced across the globe. In 2017, the World Health Organization strongly suggested reducing antibiotic use in animals used in the food industry. The use of antibiotics for growth promotion purposes was banned in the European Union from 2006, and the use of sub-therapeutic doses of medically important antibiotics in animal feed and water to promote growth and improve feed efficiency became illegal in the United States on 1 January 2017, through regulatory change enacted by the Food and Drug Administration (FDA), which sought voluntary compliance from drug manufacturers to re-label their antibiotics.
To retrace, while natural antibiotics or antibacterials were known to ancient man, came to the fore during World War II to help treat war time casualties. It is recorded that antibiotics were first used in farming towards the end of the war, in the form of intra-mammary penicillin preparations to treat bovine mastitis. At that time, milk was seen as an agricultural product which was highly susceptible to bacterial contamination, and farmers welcomed the opportunity to 'purify' their produce for the safety of consumers; it was only later that concern switched from the bacterial load of the product to the residues that might result from untimely or unregulated treatment.
The use of antibiotics to treat and prevent disease has followed a similar path to that used in human medicine in terms of therapeutic and metaphylactic applications to treat and manage disease and improve population health, and the application of case-by-case strategic preventative treatments when animals are deemed at particular risk. However, in the late 1940s, studies examining the supplementation of B12 in chicks' diets found that B12 produced from the fermentation of Streptomyces aureofaciens, an antibiotic for use in human medicine, produced a better weight gain for chicks than B12 supplied from other sources, and a reduced amount of feed to bring the birds to market weight. Further studies on other livestock species showed a similar improved growth and feed efficiency effect with the result that as the cost of antibiotics came down, they were increasingly included at low ('sub-therapeutic') levels in livestock feed as a means of increasing production of affordable animal protein to meet the needs of a rapidly-expanding post-war population. This development coincided with an increase in the scale of individual farms and the level of confinement of the animals on them, and so routine preventative antibiotic treatments became the most cost-effective means of treating the anticipated disease that could sometimes arise as a result. Veterinary medicine increasingly embraced the therapeutic, metaphylactic and strategic preventative use of antibiotics to treat disease. The routine use of antibiotics for growth stimulation and disease prevention also grew.
Antibiotic usage in the UK has been banned since 2006 – however in 2017, 73% of all antibiotics sold globally were used in animals for food production.
Bacitracin | Peptide | Beef cattle, chickens, swine, and turkeys; promotes egg production in chickens |
Bambermycin | Beef cattle, chickens, swine, and turkeys. | |
Carbadox | Swine | |
Colistin | Swine | |
Laidlomycin | Beef cattle | |
Lasalocid | Ionophore | Beef cattle |
Lincomycin | Chickens and swine | |
Monensin | Ionophore | Beef cattle and sheep; promotes milk production in dairy cows |
Neomycin/ Oxytetracycline | Beef cattle, chickens, swine, and turkeys | |
Penicillin | Chickens, swine, and turkeys | |
Roxarsone | Chickens and turkeys | |
Salinomycin | Ionophore | |
Tylosin | Chickens and swine | |
Virginiamycin | Peptide | Beef cattle, chickens, swine, turkeys |
Bacteria from the same ecological niche as antibiotic-producing organisms have evolved ancient mechanisms to withstand the effect of the harmful antibiotics. Bacteria are still able to thrive in the presence of many environmental treats, including antibiotics. This unique ability is referred to as genetic plasticity. Bacteria have two mechanism by which their genetics information can be altered to make them more resistant to treats - either by the mutation of their genes or by the acquisition of foreign DNA, which code for resistant genes. The latter being the most important cause of antibiotic-resistant strains of bacteria in animals and humans. Bacteria may acquire these foreign genes through three processes: transformation, transduction and conjugation.
Transformation is the process by which bacteria acquire naked DNA from the environment. In transduction, bacteria acquire DNA from viruses via bacteriophages. Conjugation is the direct transfer of DNA through cell-to-cell contact which is often mediated by plasmids. Conjugative plasmids carry a number of beneficial gene and enable bacteria to exchange them among themselves to improve survival against antibiotics. This contributes to multi-drug resistant bacteria.
Antibiotic resistance also occurs naturally, as it is a bacterium's response to any threat. Antibiotic-resistant bacteria have been found in pristine environments unrelated to human activity such as in the frozen and uncovered remains of woolly mammoths, in the polar ice caps and in isolated caves deep underground. Antibiotic resistance can occurs if the bioavailability of antibiotics are too low to inhibit bacterial growth, which can trigger cellular responses in the bacteria that allow them to survive. These bacteria can then reproduce and spread their antibiotic-resistant genes to other generations, increasing their prevalence and ultimately leading to infections that cannot be healed by antibiotics.
The European Medicines Agency (EMA) Antimicrobial Advice Ad Hoc Expert Group (AMEG) also published an updated categorisation of different antibiotics in veterinary medicine by the antibiotic resistance risk to humans of using them alongside the need to treat disease in animals for health and welfare reasons. The categorisation specifically focuses on the situation in Europe. Category A ('Avoid') antibiotics are designated as 'not appropriate for use in food producing animals'. Category B ('Restrict') products, also known as Highest Priority Critically Important Antibiotics, are only to be used as a last resort. These include quinolones (such as fluoroquinolones), 3rd and 4th generation cephalosporins, and polymyxins, including colistin. A new intermediate Category C ('Caution') has been created for antibiotics which should be used when there is no available product in Category D ('Prudence') that would be clinically effective. Category C includes macrolides and aminoglycosides, with the exception of spectinomycin, which remains in Category D.
Evidence for the transfer of macrolide-resistant microorganisms from animals to humans has been scant, and most evidence shows that pathogens of concern in human populations originated in humans and are maintained there, with rare cases of transference to humans. Macrolides are also extremely useful in the effective treatment of some Mycoplasma species in poultry, Lawsonia in pigs, respiratory tract infections in cattle and in some circumstances, lameness in sheep.
The use of antibiotics in livestock also has the potential to introduce antibiotic-resistant bacteria to humans via environmental exposure or inhalation of airborne bacteria. Antibiotics given to livestock in sub-therapeutic concentrations to stimulate growth when there is no diagnosis of disease – a practice still permitted in some countries – may kill some, but not all, of the bacterial organisms in the animal, possibly leaving those that are naturally antibiotic-resistant in the environment. Hence the practice of using antibiotics for growth stimulation could result in selection for resistance. Antibiotics are not fully digested and processed in the animal or human gut, therefore, an estimated 40–90% of the antibiotics ingested are excreted in urine and/or faeces. This means that as well as finding antibiotics in human sewage and animal manure, both can also contain antibiotic-resistant bacteria which have developed in vivo or in the environment. When animal manures are stored inadequately or applied as fertiliser, this can then spread bacteria to crops and into run-off water. Antibiotics have been found in small amounts in crops grown in fertilised fields, and detected in runoff from animal waste-fertilised land. Composting has been shown to reduce the presence of various antibiotics by 20–99%, but one study found that chlortetracycline, an antibiotic used in livestock feed in China, degraded at different rates dependent on the animal it was fed to, and that manure composting was not sufficient to ensure the microbial degradation of the antibiotic.
Public Health Impact and Antimicrobial Resistance
The widespread use of antibiotics in livestock is closely linked to the growing threat of antimicrobial resistance (AMR) in humans. When animals are routinely administered antibiotics—particularly for growth promotion or disease prevention—resistant bacteria can develop. These bacteria may spread to humans through several pathways, including the food supply, direct animal contact, and environmental contamination, such as water runoff from farms.
Transmission through foodborne routes is considered especially significant in industrialized countries. Pathogens like Salmonella enterica, Campylobacter jejuni, Campylobacter coli, and Yersinia enterocolitica are typically transmitted via contaminated food. For other resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), direct contact between humans and animals is the primary mode of transmission. Title: Antibiotic Resistance—Linking Human and Animal Health
Author: H. C. Wegener
Publisher: National Academies Press (US)
Date: 2012
Website name: NCBI Bookshelf
URL: https://www.ncbi.nlm.nih.gov/books/NBK114485/
Access date: 22 March 2025
Additionally, bacteria and antibiotic residues from food-animal production are widely dispersed into the environment, primarily through manure. This environmental contamination affects local microbial communities and wildlife, turning both into potential reservoirs for resistance. These environmental sources can, in turn, reintroduce resistant bacteria back into human and animal populations.
Global health experts have increasingly warned of the serious consequences of AMR. According to Dame Sally Davies, the United Kingdom's Special Envoy on Antimicrobial Resistance, more than 1.2 million people die each year from drug-resistant infections, with antibiotic use in animal agriculture being a significant contributing factor. The Review on Antimicrobial Resistance, chaired by Jim O’Neill, projected that without bold policies, annual deaths from AMR could rise to 10 million by 2050—surpassing current cancer mortality. Title: Tackling Drug-Resistant Infections Globally: Final Report and Recommendations
Author: Jim O’Neill
Publisher: The Review on Antimicrobial Resistance
Date: May 2016
Website name: AMR Review
URL: https://amr-review.org/sites/default/files/160518_Final%20paper_with%20cover.pdf
Access date: 22 March 2025
The World Health Organization (WHO) supports these projections, estimating that AMR could lead to 10 million deaths annually by 2050 if no action is taken.World Health Organization (2019)
Title: New report calls for urgent action to avert antimicrobial resistance crisis
Author: World Health Organization
Publisher: WHO
Date: 29 April 2019
Website name: World Health Organization
URL: https://www.who.int/news/item/29-04-2019-new-report-calls-for-urgent-action-to-avert-antimicrobial-resistance-crisis
Access date: 22 March 2025
Title: New report calls for urgent action to avert antimicrobial resistance crisis
Author: World Health Organization
Publisher: WHO
Date: 29 April 2019
Website name: World Health Organization
URL: https://www.who.int/news/item/29-04-2019-new-report-calls-for-urgent-action-to-avert-antimicrobial-resistance-crisis
Access date: 22 March 2025
Title: New report calls for urgent action to avert antimicrobial resistance crisis
Author: World Health Organization
Publisher: WHO
Date: 29 April 2019
Website name: World Health Organization
URL: https://www.who.int/news/item/29-04-2019-new-report-calls-for-urgent-action-to-avert-antimicrobial-resistance-crisis
Access date: 22 March 2025
Recognizing the interconnectedness of human, animal, and environmental health, the WHO and other international bodies emphasize the need for a coordinated "One Health" approach to mitigate the spread of antimicrobial resistance. This strategy calls for global cooperation across sectors to improve antibiotic stewardship, strengthen surveillance systems, and promote sustainable alternatives to antibiotic use in agriculture.
However, the World Organisation for Animal Health has acknowledged the need to protect antibiotics but argued against a total ban on antibiotic use in animal production. A total ban on antibiotics might drastically reduce protein supply in some parts of the world,
Although quantifying health benefits may be difficult, the economic impact of antibiotic restriction in animals can also be evaluated through the economic impact of antibiotic resistance in humans, which is a significant outcome of antibiotic use in animals. The World Health Organization identifies antibiotic resistance as a contributor to longer hospital stays and higher medical costs. When infections can no longer be treated by typical first-line antibiotics, more expensive medications are required for treatment. When illness duration is extended by antibiotics resistance, the increased health care costs create a larger economic burden for families and societies. The Center for Infectious Disease Research and Policy estimates approximately $2.2 billion in antibiotic resistance- related healthcare costs each year. So while restricting antibiotics in animals causes a significant economic burden, the outcome of antibiotic resistance in humans that is perpetuated by antibiotic use in animals carries comparable economic burdens.
In 2012, U.S. News & World Report described the Chinese government's regulation of antibiotics in livestock production as "weak".
On the UK 5-Year Antimicrobial Resistance (AMR) Strategy 2013–2018, the importance of addressing AMR negative effects on animal health has been considered as same as human health. Several scientific partnerships with low-middle income countries would be established. UK-China Newton fund has started to build multi-discipline collaboration cross the border to stop the increasing global burden caused by AMR. To achieve the goal of citizen public health and food safety, "The National action Plan on Controlling Antibiotic-Resistance Bacteria on animal origins (2016–2020)" has been published by Ministry of Agriculture and Rural Affairs of People's Republic of China since 2017. This plan is fully integrated with the concept of one health. It covers not only the research and development, but also social context.
In 2011, the European Parliament voted for a non-binding resolution that called for the end of the preventative use of antibiotics in livestock.
A revised regulation on veterinary medicinal products, proposed in procedure 2014/0257/COD, proposed limiting the use of antibiotics in prophylaxis and metaphylaxis. An agreement on the regulation between the Council of the European Union and the European Parliament was confirmed on 13 June 2018, and the new Veterinary Medicines Regulation (Regulation (EU) 2019/6) is due to come into effect on 28 January 2022.
While sales data give an overview of levels of use, products are often licensed for use in many species and therefore it is not possible to determine levels of use in different species without more specific usage data from each sector. In 2011, British Poultry Council members, representing 90% of the UK poultry meat industry, formed a stewardship programme that started recording antibiotics used to treat birds in the poultry meat sector in 2012. The first report was published in 2016 and reported a 44% reduction in antibiotic use between 2012 and 2015. Since then, the organisation has produced three further reports, with the 2019 report confirming that the sector is maintaining reductions of over 80% in total use since it started its stewardship group, as well as reducing use of Highest Priority Critically Important Antibiotics by over 80% by stopping use of 3rd and 4th generation cephalosporins in 2012 and colistin in 2016, and only using macrolides and fluoroquinolones as a last resort. Preventative use of antibiotics has also stopped.
As many products are licensed for use in poultry and pigs, the increasing transparency around use in the UK poultry meat sector motivated the UK pig sector to set up a stewardship programme in 2016 through the National Pig Association. In 2017, an electronic Medicine Book for pigs (eMB-Pigs) was launched by levy body Agriculture and Horticulture Development Board. eMB-Pigs provides a centralised electronic version of the existing paper or electronic medicine book kept on farms, and allows pig producers to record and quantify their individual use of medicines for easy review with the veterinary surgeon, at the same time as capturing use on each farm so that data can be collated to provide national usage figures. After it became a requirement of Red Tractor farm assurance for pigs that annual, aggregated records of antibiotic use must be logged on the eMB system, data released May 2018 showed that according to records covering 87% of the UK slaughter pig population, antibiotic use had halved between 2015 and 2017, Data for 2018 confirms that overall antibiotic use in the UK pig sector fell further, by 60% from the estimated 2015 figure, to 110 mg/kg. Use of Highest Priority Critically Important Antibiotics also fell to 0.06 mg/kg, a reduction of 95% from 2015, with use of colistin almost nil.
Factors such as levels of infectious disease domestically or internationally, weather and vaccine availability can all affect antibiotic use. For example, the Scottish salmon farming sector worked with Government and researchers to introduce a vaccine for the disease Furunculosis ( Aeromonas salmonicida) in 1994, which significantly reduced the need for antibiotic treatments, but the trout sector is still without an effective vaccine for this disease. Lack of data can also make it difficult for farmers to know they compare with their peers or what they need to focus on, a particular problem for the sheep and cattle sectors in the UK, which are in the process of trying to set up their own electronic medicines hub to capture data.
In 2004 the Government Accountability Office (GAO) heavily critiqued the FDA for not collecting enough information and data on antibiotic use in factory farms. From this, the GAO concluded the FDA did not have enough information to create effective policy changes regarding antibiotic use. In response, the FDA said more research was being conducted and voluntary efforts within the industry would solve the problem of antibiotic resistance. However, by 2011, a total of of antimicrobials were sold for use in food-producing animals in the United States, which represented 80% of all antibiotics sold or distributed in the United States.
In March 2012, the United States District Court for the Southern District of New York, ruling in an action brought by the Natural Resources Defense Council and others, ordered the FDA to revoke approvals for the use of antibiotics in livestock that violated FDA regulations. On 11 April 2012 the FDA announced a voluntary program to phase out unsupervised use of drugs as feed additives and convert approved over-the-counter uses for antibiotics to prescription use only, requiring veterinarian supervision of their use and a prescription. In December 2013, the FDA announced the commencement of these steps to phase out the use of antibiotics for the purposes of promoting livestock growth.
In 2015, the FDA approved a new Veterinary Feed Directive (VFD), an updated guideline giving instructions to pharmaceutical companies, veterinarians and producers about how to administer necessary drugs through the animal's feed and water. Around the same time, the FDA published a report of antibiotics sold or distributed for food-producing animals which found that between 2009 and 2013, just over 60% were "medically important" drugs also used in humans; the rest were from drug classes like ionophores, which are not used in human medicine. Following this, the FDA asked drug companies to voluntarily edit its labels to exclude growth promotion as an indication for antibiotic usage. It subsequently reports that "Under Guidance for Industry (GFI) #213, which went into effect January 1, 2017, antibiotics that are important for human medicine can no longer be used for growth promotion or feed efficiency in cows, pigs, chickens, turkeys, and other food animals."Summary Report On Antimicrobials Sold or Distributed for Use in Food-Producing Animals. (2018). US Food and Drug Administration. Retrieved from
Because of concerns about antibiotics residues getting into the milk or meat of cattle, in the United States, the government requires a withdraw period for any animal treated with antibiotics before it can be slaughtered, to allow residue to exit the animal.
Some grocery stores have policies about antibiotic use in the animal whose produce they sell. In response to consumer concerns about the use of antibiotics in poultry, Perdue Farms removed all human antibiotics from its feed in 2007 and launched the Harvestland brand, under which it sold products that met the requirements for an "antibiotic-free" label. In 2012 in the United States advocacy organization Consumers Union organized a petition asking the store Trader Joe's to discontinue the sale of meat produced with antibiotics.
The CDC and FDA do not now support the use of antibiotics for growth promotion because of evidence suggesting that antibiotics used for growth promotion purposes could lead to the development of resistant bacteria. In addition to this, The Pew Charitable Trusts has stated that "hundreds of scientific studies conducted over four decades demonstrate that feeding low doses of antibiotics to livestock breeds antibiotic-resistant superbugs that can infect people". The FDA, the U.S. Department of Agriculture and the Centers for Disease Control and Prevention have all testified before Congress that there is a definitive link between the routine, non-therapeutic use of antibiotics in food animal production and the challenge of antibiotic resistance in humans." However, the National Pork Board, a government-owned corporation of the United States, has said: "The vast majority of producers use (antibiotics) appropriately." In 2011 the National Pork Producers Council, an American trade association, also said, "Not only is there no scientific study linking antibiotic use in food animals to antibiotic resistance in humans, as the US pork industry has continually pointed out, but there isn't even adequate data to conduct a study."*
It is difficult to set up a comprehensive surveillance system for measuring rates of change in antibiotic resistance. The US Government Accountability Office published a report in 2011 stating that government and commercial agencies had not been collecting sufficient data to make a decision about best practices. There is also no regulatory agency in the United States that systematically collects detailed data on antibiotic use in humans and animals, which means it is not clear which antibiotics are prescribed for which purpose and at what time. While this may be lacking at a regulatory level, the US poultry meat sector has been working on the issue of data collection itself, and has now reported comparative data showing significant reductions in antibiotic use. Among the highlights in the report was a 95% decrease in in-feed tetracycline use in broiler chicks from 2013 to 2017, a 67% reduction in in-feed use of tetracycline in turkeys, and a 42% drop in hatchery use of gentamicin in turkey poults. This is an encouraging sign; the 53% overall reduction in antibiotic use seen in the UK between 2013 and 2018 was initiated from a voluntary stewardship programme developed by the UK poultry meat sector.
Probiotics, cultures of a single bacteria strain or mixture of different strains, are being studied in livestock as a production enhancer.
Prebiotics are non-digestible carbohydrates. The carbohydrates are mainly made up of oligosaccharides which are short chains of monosaccharides. The two most commonly studied prebiotics are fructooligosaccharides (FOS) and mannanoligosaccharides (MOS). FOS has been studied for use in chicken feed. MOS works as a competitive binding site, as bacteria bind to it rather than the intestine and are carried out.
Bacteriophages are able to infect most bacteria and are easily found in most environments colonized by bacteria, and have been studied as well.
In another study it was found that using probiotics, competitive exclusion, enzymes, immunomodulators and organic acids prevents the spread of bacteria and can all be used in place of antibiotics.Doyle, M.E. 2001: Alternatives to Antibiotic Use for Growth Promotion in Animal Husbandry. Food Research Institute, University of Wisconsin-Madison. Another research team was able to use bacteriocins, antimicrobial peptides and bacteriophages in the control of bacterial infections. While further research is needed in this field, alternative methods have been identified in effectively controlling bacterial infections in animals.
Other alternatives include preventative approaches to keep the animals healthier and so reduce the need for antibiotics. These include improving the living conditions for animals, stimulating natural immunity through better nutrition, increasing biosecurity, implementing better management and hygiene practices, and ensuring better use of vaccination.
/ref> and when use of antibiotics is reduced or eliminated in livestock through legislation or voluntarily, both animal health and welfare and economic impacts can be negatively affected. For example, experiences from farms where antibiotic use has been cut back or eliminated in the interests of meeting a consumer demand for 'antibiotic-free' or 'reared without antibiotics' produce have been shown to have a detrimental effect on animal health and welfare. When antibiotics are used sub-therapeutically (for animal performance, increased growth, and improved feed efficiency), then the costs of meat, eggs, and other animal products are lowered. One big argument against the restriction of antibiotic use is the potential economic hardship that would result for producers of livestock and poultry that could also result in higher cost for consumers. In a study analysing the economic cost of the FDA restricting all antibiotic use in animal livestock, it was estimated that the restriction would cost consumers approximately $1.2 billion to $2.5 billion per year. In order to determine the overall economic impact of restricting antibiotic use, the financial cost must be weighed against the health benefits to the population. Since it is difficult to estimate the value of potential health benefits, the study concluded that the complete economic impact of restricting antibiotic use has not yet been determined.
Use and regulation by country
Brazil
Canada
China
European Union
India
New Zealand
/ref>
Compared to other countries, New Zealand has a very low prevalence of AMR in animals and plants. This is due to their low use of antibiotics in animal treatment.
South Korea
United Kingdom
United States
target="_blank" rel="nofollow">[3] These new 2017 guidelines for instance prohibited using a drug off-label for non-therapeutic purposes, which would make using the re-labeled drug for growth enhancement illegal. In addition, some drugs were reclassified from 'Over the Counter' (OTC) to 'Veterinary Feed Directive' (VFD); VFD drugs require a veterinarian's authorization before they can be delivered in feed. As a result, the FDA reported a 33% decrease from 2016 to 2017 in domestic sales of medically important antibiotics for use in livestock. Despite this progress, the Natural Resources Defense Council (NRDC) remains concerned that sales of antibiotics to the beef and pork industries remain elevated in 2017 compared with the poultry industries, and their use could still primarily be for preventing diseases in healthy animals, which further increases the threat on antibiotic resistance.Dall C. (2018). FDA reports major drop in antibiotics for food animals. CIDRAP News. Retrieved from http://www.cidrap.umn.edu/news-perspective/2018/12/fda-reports-major-drop-antibiotics-food-animals However, the FDA policy remains the same as it stated in 2013:
The statement was issued in response to a United States Government Accountability Office report that asserts: "Antibiotic use in food animals contributes to the emergence of resistant bacteria that may affect humans".
Research into alternatives
See also
External links
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