Antibiotic use in livestock
Antibiotic use in livestock is the use of antibiotics for any purpose in the husbandry of livestock, which includes treatment when ill (therapeutic), treatment of a batch of animals when at least one is diagnosed as ill (metaphylaxis, similar to the way bacterial meningitis is treated in children), and preventative treatment (prophylaxis). The use of subtherapeutic doses in animal feed and water to promote growth and improve feed efficiency is discouraged by the FDA as part of their Veterinary Feed Directive, which seeks voluntary compliance from drug manufacturers to re-label their antibiotics. Nevertheless this article focuses on the use of antibiotics for growth promotion, which has been banned in Europe since 2006, and on legislation regarding antibiotic use in farm animals in the USA.
In 2013, the CDC finalized and released a report detailing antibiotic resistance and classified the top 18 resistant bacterium as either being urgent, serious or concerning threats. Of those organisms, three (C. diff, carbapanem-resistant enterobacteriaceae, and Neisseria gonorrhoeae) have been classified as urgent threats and require more monitoring and prevention. In the US alone, more than 2 million people are diagnosed with antibiotic-resistant infections and over 23,000 die per year due to resistant infections.
Given the concerns about antibiotic use for feed conversion, research into alternatives is ongoing.
- 1 History
- 2 Growth stimulation
- 3 Concentrated animal feeding operations
- 4 Use and regulation by country
- 5 Antibiotic resistance
- 6 Research into alternatives
- 7 See also
- 8 References
- 9 External links
In 1910 in the United States, a meat shortage resulted in protests and boycotts. After this and other shortages, the public demanded government research into stabilization of food supplies. Since the 1900s, livestock production on United States farms has had to rear larger quantities of animals over a short period of time to meet new consumer demands. Factory farming originated in the late 19th century when advances in technology and science allowed for mass production of livestock. Global agriculture production doubled four times within 1820 and 1975, feeding one billion in 1800 and up to 6.5 billion in 2002.[page needed] The increase in animal densities brought the threat of disease, necessitating greater disease control. In 1950, a group of United States scientists found that adding antibiotics to animal feed increases the growth rate of livestock. American Cyanamid published research establishing the practice.
By 2001, this practice had grown so much that a report by the Union of Concerned Scientists found that nearly 90% of the total use of antimicrobials in the United States was for non-therapeutic purposes in agricultural production.
Certain antibiotics, when given in low, sub-therapeutic doses, are known to improve feed conversion efficiency (more output, such as muscle or milk, for a given amount of feed) and may promote greater growth, most likely by affecting gut flora. The drugs listed below are used to increase feed conversion ratio and weight gain. Some drugs listed below are ionophores, which are not antibiotics and do not pose any potential risk to human health.
|Antibiotic Growth Promoters used in Livestock Production|
|Bacitracin||Peptide||Beef cattle, chickens, swine, and turkeys; promotes egg production in chickens|
|Bambermycin||Beef cattle, chickens, swine, and turkeys.|
|Lincomycin||Chickens and swine|
|Monensin||Ionophore||Beef cattle and sheep; promotes milk production in dairy cows|
|Neomycin/ oxytetracyclinee||Beef cattle, chickens, swine, and turkeys|
|Penicillin||Chickens, swine, and turkeys|
|Roxarsone||Chickens and turkeys|
|Tylosin||Chickens and swine|
|Virginiamycin||Peptide||Beef cattle, chickens, swine, turkeys|
Concentrated animal feeding operations
Concentrated animal feeding operations (CAFO) refer to large, often multi-species, farming operations which lead to close animal housing quarters, rampant infections and disease, among many other malaises.
These animals are sedentary due to the lack of space in the cramped cages. They often catch disease due to the packed rooms and ease of transmission among the manure, blood and bodily fluids. The current justification for these conditions is the belief that due to the animals not roaming, they save energy, and therefore better digest their food; this energy is reserved for growth of the animals.
The large amounts of manure produced in cattle livestock populations are a problem for many CAFOs. Dependent on size of the operation, there can be 2,800 to 1.6 million tons of manure produced per year. Annually, the livestock population in the United States produces 3 to 20 times more manure than people. However, many operations lack ultimate sewage treatment.
The manure produced from concentrated populations of animals can be diseased and have negatives impact on the environment itself. Livestock manure can be tainted by blood, pathogens such as E. coli, antibiotics, growth hormones, chemical additives, etc. Some of this manure can be treated and used as fertilizer by liquefying and spraying it, but larger operations often revert to storing it until it can be disposed of properly. Manure is also trucked off site, stored in containers, or held in holding ponds. There can be problems associated with storing manure; manure can have detrimental effects on the surrounding area due to leaking containers or holding ponds. This, known as manure leaching, can lead to manure run-off affecting the ground or soil water by percolation or direct contamination.
When manure run-off or percolation enters a water system, the infecting agents thrive in that environment. Previous studies have shown private well water in Idaho found high levels of veterinary antibiotics as well as additive chemicals. The surrounding areas of concentrated animal feeding operations are at particular risk for groundwater or soil water sources of contamination. When manure enters a water source, either underground or above ground, whatever pathogens inhabiting the manure enters the water as well. All the agents inside the manure can contaminate a water source. Pathogens survive longer in groundwater than surface water due to lower temperatures and protection from the sun and other harsher elements. Additionally, this water will not be treated until far later in the process, allowing bacterial colonies to grow.
Groundwater is one of the larger sources of water that humans are supplied from. As of 2010, 53% of people in the United States relied on groundwater as their primary source of drinking water. Groundwater also gradually leads to surface waters, such as rivers and streams. Water as a contaminant is a major source of outbreak in human populations – the areas around concentrated animal feeding operations are typically at a higher risk of exposure to antibiotic-resistant bacteria strains and subsequent outbreaks.
The living conditions of animal feeding operations leads to a shotgun approach at targeting a sick population of livestock. Due to denser amounts of animals in smaller spaces, illness spreading and affecting a few animals can signal a precursor that more animals in an area will be infected by pathogens. In the United States, 80% of all antibiotics are given as feed additives. The antibiotics given to treat all the animals in dense area are not specific to each animal's illness and use a general approach to dosing. This leads to the antibiotics not being fully metabolized by the animals. This has been tested by levels of antibiotics still present in the manure of these animals.
A vector, in this context, is an organism that transmits disease to another organism. Insects such as flies and mosquitoes have high amounts of breeding grounds and nests of eggs around manure waste, allowing rapid reproduction and fresh vectors for potential disease. Typically with dense populations of livestock, transmission of disease from one animal to another can be on account of insects, such as flies, mosquitoes or ticks, spreading blood from one animal to another.[not in citation given] This can be particularly dangerous for sick animals spreading diseases to healthier animals, promoting general malaise in a concentrated area. Additionally, the animals can be infected from other animals' manure making contact with their food; fecal-oral transmission are one of the largest sources for pathogen transmission. Within concentrated animal farming operations, there is no mandatory testing of novel viruses, only reporting known illnesses to the World Organization for Animal Health. Thus, certain mutations or recombinant bacteria strains, which are more efficient in translation to human to human events, can be unnoticed.
Additionally, insect beds around manure pools or containers are a particular threat for contamination. These insects feed and reproduce in the runoff of treated manure, so they can acquire resistant strains of bacteria from blood and the manure of livestock treated with antibiotics. Since most manure holding ponds are on or near the sites of the operations, the insects are not far from livestock populations. These insects are also particularly dangerous because they can spread bacteria or other pathogens to humans by infecting human food. This is prevalent when treated manure is used as fertilizers of liquefied for spraying and as a result of the unsanitary handling of meat in kitchens.
Use and regulation by country
The use of drugs in food animals is regulated in nearly all countries. Historically, this has been to prevent alteration or contamination of meat, milk, eggs and other products with toxins that are harmful to humans. Treating a sick animal with drugs may lead to some of those drugs remaining in the animal when it is slaughtered or milked. Scientific experiments provide data that shows how long a drug is present in the body of an animal and what the animal's body does to the drug. Of particular concern are drugs that may be passed into milk or eggs. By the use of "drug withdrawal periods: before slaughter or the use of milk or eggs from treated animals, veterinarians and animal owners ensure that the meat, milk and eggs is free of contamination.
Brazil is the world's largest exporter of beef. The government regulates antibiotic use in the cattle production industry.
China produces and consumes the most antibiotics of all countries. Antibiotic use has been measured by checking the water near factory farms in China as well as through animal feces. It was calculated that 38.5 million kg (or 84.9 million lbs) of antibiotics were used in China's swine and poultry production in 2012. The abuse of antibiotics caused severe pollution of soil and surface water in Northern China.
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. Serval 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.
- Implementation of Exit Plan, to encourage the drop of antibiotics as the growth promoters
- Regulation of drug market, to strengthen the registration and management of veterinary antibiotics
- Improvements on AMR surveillance system
- Strengthening on the testing of antibacterial residue
- Exemplification on effective models of decreasing the use on antibiotics
- Education on public and professions
In 1999, the European Union (EU) implemented an antibiotic resistance monitoring program and a plan to phase out antibiotic use for the purposes of growth promotion by 2006. The European Union banned the use of antibiotics as growth agents starting on 1 January 2006 with Regulation (EC) No 1831/2003. In Germany, 1,734 tons of antimicrobial agents were used for animals in 2011 compared with 800 tons for humans. Sweden banned their use in 1986 and Denmark started cutting down drastically in 1994, now using 60% less. In the Netherlands, the use of antibiotics to treat diseases increased after the ban on its use for growth purposes in 2006.
In 2011, the European Parliament voted for a non-binding resolution that called for the end of pre-emptive use of antibiotics in livestock.
A revised regulation on veterinary medicinal products, proposed in procedure 2014/0257/COD, would limit 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.
In 2011 the Indian government proposed a "National policy for containment of antimicrobial resistance". Other policies set schedules for requiring that food producing animals not be given antibiotics for a certain amount of time before their food goes to market. A study released by Centre for Science and Environment (CSE) on 30 July 2014 found antibiotic residues in chicken. This study claims that Indians are developing resistance to antibiotics – and hence falling prey to a host of otherwise curable ailments. Some of this resistance might be due to large-scale unregulated use of antibiotics in the poultry industry. CSE finds that India has not set any limits for antibiotic residues in chicken and says that India will have to implement a comprehensive set of regulations including banning of antibiotic use as growth promoters in the poultry industry. Not doing this will put lives of people at risk.
In 1999 the New Zealand government issued a statement that they would not then ban the use of antibiotics in livestock production. In 2007 ABC Online reported on antibiotic use in chicken production in New Zealand.
In 1998 some researchers reported use in livestock production was a factor in the high prevalence of antibiotic-resistant bacteria in Korea. In 2007 The Korea Times noted that Korea has relatively high usage of antibiotics in livestock production. In 2011, the Korean government banned the use of antibiotics as growth promoters in livestock.
In 1970 the FDA started recommending that antibiotic use in livestock be limited but set no actual regulations governing this recommendation. By 2001, the Union of Concerned Scientists estimated that greater than 70% of the antibiotics used in the U.S. are given to food animals (for example, chickens, pigs, and cattle), in the absence of disease.
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 that the FDA does not have enough information to create effective policy changes regarding antibiotic use. In response, the FDA insisted that more research was being conducted and voluntary efforts within the industry would solve the problem of antibiotic resistance.
Few policies exist that limit antibiotic use on factory farms, and some proposed legislation in the US has failed to be adopted. In 2007, two federal bills (S. 549 and H.R. 962) aimed to phase out nontherapeutic antibiotics in U.S. food animal production. The Senate bill, introduced by Sen Ted Kennedy, died. The House bill, introduced by Rep. Louise Slaughter, died after being referred to Committee. The U.S. Animal Drug User Fee Act was passed by Congress in 2008, requiring that drug manufacturers report all sales of antibiotics into the food animal production industry.
By 2011, a total of 13.6 million kg (30 million lb) 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. Of the antibiotics given to animals from 2009 through 2013, just above 60% distributed for food animal use are "medically-important" drugs that are also used in humans. The rest were drug classes like ionophores, which are not used in human medicine.
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.
Numerous state senators and members of congress showed support for the Preservation of Antibiotics for Medical Treatment Act of 2013 and Preventing Antibiotic Resistance Act of 2015. These acts proposed amendments be made to the Federal Food, Drug and Cosmetic Act which would limit and preserve the use of antibiotics for medically necessary situations. Both of these bills died in Congress in 2015.
In 2015, the FDA approved a new Veterinary Feed Directive (VFD), which is an updated guideline that give instructions to pharmaceutical companies, veterinarians, and producers about how to administer necessary drugs through the animal's feed and water. The FDA has asked drug companies to voluntarily edit its labels to exclude growth promotion as an indication for antibiotic usage. FDA regulations on off-label use prohibit using a drug off-label for non-therapeutic purposes, which would make using the re-labeled drug for growth enhancement illegal. Some drugs are also being re-classified from OTC to VFD; VFD drugs require a veterinarian's authorization before it can be delivered in feed. The new guidelines took effect on 1 January 2017.
The key aspect of FDA’s strategy is the request that animal drug sponsors (those who own the right to market the product) voluntarily work with FDA to revise the approved use conditions for their medically important antimicrobial drug products to remove production uses (such as growth enhancement or feed efficiency), and bring the remaining therapeutic uses under veterinary oversight. Once manufacturers voluntarily make these changes, products can no longer be used for production purposes and therapeutic use of these products would require veterinary oversight.
Some grocery stores have policies about voluntarily not selling meat produced by using antibiotics to stimulate growth. In response to consumer concerns about the use of antibiotics in poultry, Perdue 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. By 2014, Perdue had also phased out ionophores from its hatchery and began using the "antibiotic free" labels on its Harvestland, Simply Smart, and Perfect Portions products. By 2015, 52% of the company's chickens were raised without the use of any type of antibiotics.
There has been increased concern about the use of anti-microbials in animals (including pets, livestock, and companion animals) contributing to the rise in antibiotic-resistant infections in humans. Around 70% of all antibiotics administered are used for livestock. Some drugs are used in livestock feed to prevent illnesses and or increase growth rates, but others are used as treatment for illnesses. The use of antibiotics in livestock can bring antibiotic-resistant bacteria to humans via consumption of meat and ingestion through airborne bacteria. Manure from food-producing animals can also contain antibiotic-resistant bacteria and is sometimes stored in lagoons. This waste is often sprayed as fertilizer and can thus contaminate crops and water with the bacteria.
The World Health Organization has published a list, "Critically Important Antimicrobials for Human Medicine", with the intent that it be used "as a reference to help formulate and prioritize risk assessment and risk management strategies for containing antimicrobial resistance due to human and non-human antimicrobial use."
Effects in humans
The effects of antibiotic usage in livestock transferring to humans has been well documented for over 40 years. It was first documented in 1976, where a study followed a novel antibiotic being used in livestock. The bacteria in animals and workers were regularly followed to record translational effects. The findings revealed that within 2 weeks, the bacteria found in the guts of animals fed antibiotics were resistant to the new antibiotic. Additionally, the resistant bacteria had spread to farm's laborers within 6 months. The bacteria in the stool of the laborers were tested and contained more than 80% resistance to the initial antibiotic given to the livestock. Since the primary study, there have been many well-documented events showing that antibiotic usage in livestock results in direct influence of antibiotic resistance in humans.
Major bacterial infections in humans can be traced back to livestock. The family Enterobacteriaceae includes many opportunistic bacteria, including E. coli, which are commonly found in livestock. Other bacteria include Klebsiella and Staphylococcus aureus. They cause infections in the urinary tract, digestive system, skin, and bloodstream, and account for a significant portion of antibiotic-resistant bacterial infections.
Advocates for restricting antibiotic use
The practice of using antibiotics for growth stimulation is problematic for these reasons:
- It is the largest use of antimicrobials worldwide
- Subtherapeutic use of antibiotics results in bacterial resistance
- Every important class of antibiotics are being used in this way, making every class less effective
- The bacteria being changed harm humans
Donald Kennedy, former director of the FDA, has said "There's no question that routinely administering non-therapeutic doses of antibiotics to food animals contributes to antibiotic resistance." David Aaron Kessler, another former director, stated, "We have more than enough scientific evidence to justify curbing the rampant use of antibiotics for livestock, yet the food and drug industries are not only fighting proposed legislation to reduce these practices, they also oppose collecting the data."
In 2013, the US Centers for Disease Control and Prevention (CDC) published a white paper discussing antibiotic resistance threats in the US and calling for "improved use of antibiotics" among other measures to contain the threat to human health. The CDC asked leaders in agriculture, healthcare, and other disciplines to work together to combat the issue of increasing antibiotic resistance.
Some scientists have said that "all therapeutic antimicrobial agents should be available only by prescription for human and veterinary use."
The Pew Charitable Trusts have 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 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."
HSBC produced a report in October 2018 warning that the use of antibiotics in meat production could have “devastating” consequences for humans. It noted that many dairy and meat producers in Asia and the Americas had an economic incentive to continue high usage of antibiotics, particularly in crowded or unsanitary living conditions.
Advocates for status quo
In 2011 the National Pork Producers Council, an American trade association, has said, "Not only is there no scientific study linking antibiotic use in food animals to antibiotic resistance in humans, as the U.S. pork industry has continually pointed out, but there isn't even adequate data to conduct a study." The statement contradicts scientific consensus, and 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".
Effects of restricting antibiotic use
When government regulation restricts use of antibiotics, the negative economic impact is not often considered.
Difficulties with determining relevant facts
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.
Currently,[when?] there is no regulatory agency in the United States that systematically collects detailed data on antibiotic use in humans and animals. It is not clear which antibiotics are prescribed for which purpose and at what time. Furthermore, the world has no surveillance infrastructure to monitor emerging antibiotic resistance threats. Because of these issues, it is difficult to quantify antibiotic resistance, to regulate antibiotic prescribing practices, and to detect and respond to rising threats.
Specific resistance that has been identified
At this time,[when?] the most well-documented impact on humans is foodborne gastrointestinal illness. In most cases, these illnesses are mild and do not require antibiotics; though if the infectious bacteria is drug-resistant, they have increased virulence (ability to cause disease) and lead to prolonged illness. Furthermore, in approximately 10% of cases, the disease becomes severe, requiring more advanced treatments. These treatments can take the form of intravenous antibiotics, supportive care for blood infections, and hospital stays, leading to higher costs and greater morbidity, with a trend toward higher mortality. Though all people are susceptible, populations at higher risk for severe disease include children, the elderly, and those with chronic disease.
Over the past 20 years, the most common drug-resistant foodborne bacteria in industrialized countries have been non-typhoidal Salmonella and Campylobacter. Research has consistently shown the main contributing factors are bacteria sourced in livestock. A 1998 outbreak of multidrug-resistant Salmonella in Denmark linked back to two Danish swine herds. Coupled with the discovery of this link, there have been improved monitoring systems that have helped to quantify the impact. In the United States, it is estimated that there are approximately 400,000 cases and over 35,000 hospitalizations per year attributable to increasing resistant strains of Salmonella and Campylobacter. In terms of financial impact in the US, the treatment of non-typhoidal Salmonella infections alone is now estimated to cost $365 million per year. In light of this, in its inaugural 2013 report on antibiotic resistance threats in the United States, the CDC identified resistant non-typhoidal Salmonella and Campylobacter as "serious threats" and called for improved surveillance and intervention in food production moving forward.
There are other bacteria as well, where research is evolving and revealing that bacterial resistance acquired through use in livestock may be contributing to disease in humans. Examples of these include Enterococcus (including E. coli 0157) and Staphylococcus aureus. For foodborne illness from E. coli, which is still not typically treated with antibiotics because of associated risk of renal failure, increasing rates of antibiotic-resistant infections have been correlated with increasing virulence of the bacteria. In the case of Enterococcus and S. aureus, resistant forms of both of these bacteria have resulted in greatly increasing morbidity and mortality in the US. At this point, there have been studies, though a limited number, that definitively link antibiotic use in food production to these resistance patterns in humans and further research will help to further characterize this relationship.
Mechanisms for transfer to humans
The amounts given are termed "sub-therapeutic", i.e., insufficient to combat disease. Despite no diagnosis of disease, the administration of these drugs result in decreased mortality and morbidity and increased growth in the animals so treated. It is theorized that sub-therapeutic dosages kills some, but not all, of the bacterial organisms in the animal – likely leaving those that are naturally antibiotic-resistant. The actual mechanism by which sub-therapeutic antibiotic feed additives serve as growth promoters is thus unclear. Some people have speculated that animals and fowl may have sub-clinical infections, which would be cured by low levels of antibiotics in feed, thereby allowing the creatures to thrive.
Humans can be exposed to antibiotic-resistant bacteria by ingesting them through the food supply. Dairy products, ground beef, and poultry are the most common foods harboring these pathogens. There is evidence that a large proportion of resistant E. coli isolates causing blood stream infections in people are from livestock produced as food.
When manure from antibiotic-fed swine is used as fertilizer elsewhere, the manure may be contaminated with bacteria which can infect humans.
Sampling of retail meats such as turkey, chicken, pork and beef consistently show high levels of Enterobacteriaceae. Rates of resistant bacteria in these meats are high as well. Sources on contaminated meat put humans at direct risk by handling the meat or ingesting it before it is completely cooked. Ingesting contaminated meat sources accounts for 20% of antibiotic-resistant infections in humans. Food preservation methods can help eliminate, decrease, or prevent the growth of bacteria. 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.
Research into alternatives
Increasing concern due to the emergence of antibiotic-resistant bacteria has led researchers to look for alternatives to using antibiotics in livestock.
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.
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. 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. All of the alternative methods listed pose no known threat to human health and all can lead the elimination of antibiotics in factory farms. With further research it is highly likely that a cost effective and health effective alternative could and will be found.
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- PBS report on antibiotics in livestock production
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- Resources on antibiotic use and resistance