Antibiotic use in livestock

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Antibiotic use in livestock is the use of antibiotics for any purpose in the husbandry of livestock, which includes not only the treatment or prophylaxis of infection but also the use of subtherapeutic doses in animal feed to promote growth and improve feed efficiency in contemporary intensive animal farming. Antimicrobials (including antibiotics and antifungals) and other drugs are used by veterinarians and livestock owners to increase the size of livestock, poultry, and other farmed animals. The use of some drugs is banned in some countries due to food contamination or concern about increasing antibiotic resistance and what some consider antibiotic misuse. Other drugs may be used only under strict limits, and some organizations and authorities seek to further restrict the use of some or all drugs in animals . Other authorities, particularly those in animal industry, food animal medicine, and pharmacology industry, say that concerns for bacterial resistance in humans is overblown and restricting the availability of medicine is detrimental to animal health and the economical production of food.

History of the practice[edit]

In 1910 in the United States, a meat shortage resulted in protests and boycotts.[1][2] After this and other shortages, the public demanded government research into stabilization of food supplies.[1] 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. Along with the new large animal densities came the threat of disease, therefore requiring a greater disease control of these animals. In 1950, a group of United States scientists found that adding antibiotics to animal feed increases the growth rate of livestock.[1][3] American Cyanamid published research establishing the practice.[1]

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.[4]

Drugs and growth stimulation[edit]

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/or may promote greater growth, most likely by affecting gut flora.[5]

Antibiotic Growth Promoters used in Livestock Production
drug class effect
Bambermycin increase feed conversion ratio; growth promotion in poultry and cattle[6]
Lasalocid Ionophore increase feed conversion ratio[6]
Monensin Ionophore increase feed conversion ratio; increase weight gain in cattle and sheep[6]
Salinomycin Ionophore increase feed conversion ratio; increase weight gain[6]
Virginiamycin peptide promotes growth of poultry[6]
Bacitracin peptide promotes growth of poultry[6]

Use in different livestock[edit]

In swine production[edit]

The use of antibiotics to increase the growth of pigs is most studied of all livestock.

In production of other livestock[edit]

Organic beef comes from cattle who have not been fed antibiotics.

Regulatory context[edit]

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.

These restrictions include not only poisons or drugs (such as penicillin) which may result in allergic reactions but also contaminants which may cause cancer. It is illegal in the USA to administer drugs or feed substances to animals if they have been shown to cause cancer.

One of the main restrictions is the amount that is administered to animals in the industry. These drugs should be administered to healthy livestock at a low concentration of 200 g per ton of feed. The amount distributed is also altered throughout the lifespan of livestock in order to meet specific growth needs.[7]

Legality of the use of specific drugs in animal medicine varies according to location.

Just as in human medicine, some drugs are available over the counter and others are restricted to use only on the prescription of a veterinary physician. In the USA, the Food and Drug Administration (FDA) requires specific labels on all drugs, giving directions on the use of the drug. For animals, this includes the species, dose, reason for giving the drug (indication) and the required withdrawal period, if any. Federal law requires laypersons to use drugs only in the manner listed. Veterinarians who have examined an animal or a herd of animals may issue a replacement label, giving new directions, based on their medical knowledge. It is illegal in the USA for any layperson to administer any drug to a food animal in a way not specific to the drug label. Over-the-counter drugs which may be used by laypersons include anti-parasite drugs (including fly sprays) and antimicrobials. These drugs can be applied as sprays, creams, injections, oral pills or fluids, or as a feed additive, depending on the drug and the label.

In December 2013, the FDA updated its regulations to try to begin reducing use of antibiotics for growth enhancement.[8] Significant lobbying comes from all directions, from those against tighter regulation to those who complain it doesn't go far enough.[9]

Nearly all hormones and painkillers are illegal for laypersons to use in food animals. Additionally, there are very few drugs labelled for use in laying hens, ducks, goats, meat rabbits, or other minor species.

If a layperson gives a drug to a food animal, they are responsible for ensuring that an adequate withdrawal period is allowed to ensure that the meat or milk is not contaminated.

For drugs that can not be legally given by lay persons, or if the animal or herd does not respond to treatment, a veterinary physician may prescribe a different drug or one at a different dose than is on the label. The veterinarian will also give directions as to the appropriate withdrawal period.

How drugs are given[edit]

Drugs can be administered to animals in a variety of means, just as with humans. Among these are topical (on the skin), by injection (including intravenous, subcutaneous, subcutaneous implants, intramuscular and intraperitonial), and orally. Oral drugs can be in pill or liquid form, or can be given by mixing with feed or water. The appropriate route for treatment depends on the specific case and can vary by: illness, severity of illness, selected drug, age or condition of the animal, species of the animal, type of housing and other factors. For animals that are not regularly fed a concentrated feed or which can be handled repeatedly, a slow-release injection might be the most appropriate. Some drugs are not available or appropriate in this form and should be delivered orally. For animals that are fed regularly (rather than grazing freely) or that can not be easily handled, the most appropriate means of administering the drug may be to include the drug in feed or water. This eliminates the stress of daily (or more frequent) handling of animals, which can make the animals more ill. Poultry are most commonly medicated in this fashion, as they are easily stressed to the point of dying. Administering the drug by feed also prevents injection wounds in animals.

When drugs are given[edit]

The timely administration of drugs is key to preventing animal suffering and economic loss to the farmer. Animals which are ill can infect other animals, and may become so ill that they can not be sold. A variety of techniques are used to monitor animals for illness so that they can be treated appropriately. Stress reduction, adequate nutrition, shelter, and quarantine of incoming stock are all important factors to promote growth and reduce illness and the need for active treatment. The age and status of an animal is also important in determining correct treatment - a young animal or pregnant animal is at greater risk and are treated more aggressively than an older animal.

One complicating factor for treating illnesses in animals is the difficulty in catching a disease before a large number of animals are infected. In many significant diseases, the animal may be infectious for several days before showing signs of the illness. Others may be carriers of the disease but do not actually show illness themselves. In these cases, a flock or herd of animals may have a mix of sick animals, completely well animals, and animals which are infected but are not yet showing signs. In these cases, attempting to separate the ill animals would be of little help, as the extra stress would only serve to make the situation worse. In these cases, treating the entire group would result in the most rapid recovery of the sick animals with the least amount of suffering and death.

Use by country[edit]

European Union[edit]

Although the European Union banned the use of antibiotics as growth agent in 2006, its use has not changed much until recently. In Germany, 1,734 tons of antimicrobial agents were used for animals in 2011 compared with 800 tons for humans. On the other hand, Sweden banned their use in 1986 and Denmark started cutting down drastically in 1994, so that its use is now 60% less.[10] In the Netherlands, the use of antibiotics to treat diseases increased after the ban on its use for growth purposes in 2006.[11] In 2011, the EU voted to ban the prophylactic use of antibiotics, alarmed at signs that the overuse of antibiotics is blunting their use for humans.[12]

United States[edit]

In 1952, 2 million pounds of antibiotics were produced, by 1998 at least 50 million pounds were produced, about half of which was used for human treatment and about forty percent of which was used in animals, the "lion's share" of which was mixed into feed to promote growth.[13] in 2011 80% of antibiotics went to livestock production.[14]

China[edit]

Of all countries, China produces and consumes the most antibiotics.[15]

Antibiotic use has been measured by checking the water near factory farms in China.[16][17] Measurements have also been taken from animal dung.[18]

Half of the antibiotics manufactured in China are used in the production of livestock.[19]

India[edit]

In 2012 India manufactured about a third of the total amount of antibiotics in the world.[20]

Brazil[edit]

Brazil is the world's largest exporter of beef and the government regulates antibiotic use in the cattle production industry.[21]

South Korea[edit]

New Zealand[edit]

Concerns about antibiotic resistance[edit]

More recently, 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. The use of antimicrobials has been linked to the rise of resistance in every drug and species where it has been studied, including humans and livestock. However, the role of antibiotic use in food animals - in contrast to the use of antibiotics in humans - in the rise of resistant infections in humans is in dispute. The use of antimicrobials in various forms is widespread throughout animal industry, and is presented as key to preventing animal suffering and economic loss. It is linked by some activist groups to animal welfare concern, large scale commercial agriculture, international food trade, agricultural protectionist laws, environmental protection (including climate change) and other topics, which make the aims of some groups on both sides of the debate difficult to untangle.

Positions of advocates for restricting antibiotic use[edit]

The practice of using antibiotics for growth stimulation is problematic for these reasons:

  • it is the largest use of antimicrobials worldwide[22]
  • subtherapeutic use of antibiotics results in bacterial resistance[22]
  • every important class of antibiotics are being used in this way, making every class less effective[22]
  • the bacteria being changed harm humans[22]

Donald Kennedy, former director of the United States Food and Drug Administration, has said "There's no question that routinely administering non-therapeutic doses of antibiotics to food animals contributes to antibiotic resistance."[23] David Aaron Kessler, another former director of the FDA, said that "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."[24]

Some scientists have said that "all therapeutic antimicrobial agents should be available only by prescription for human and veterinary use."[25]

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."[26]

Moderate positions[edit]

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.[27]

Positions of advocates for status quo[edit]

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."[28] The statement contradicts scientific consensus,[29] 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".[30]

The National Pork Board, a Government-owned corporation of the United States, has said that "the vast majority of producers use (antibiotics) appropriately."[31]

Effects of restricting antibiotic use[edit]

When government regulation restricts use of antibiotics the negative economic impact is not often considered.[32]

Regulation of antibiotics in livestock production would affect the business models of corporations including Tyson Foods, Cargill, and Hormel.[33]

Difficulties with determining relevant facts[edit]

It is difficult to set up a comprehensive surveillance system for measuring rates of change in antibiotic resistance.[34] 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.[35]

Specific resistance that has been identified[edit]

In the late 1980s doctors in Europe first reported that certain bacteria were becoming resistant to vancomycin.[36] They began to study whether there was a connection between resistance and the practice of feeding a drug related to vancomycin to animals as a growth stimulant.[36] Vancomycin-resistant enterococci can spread from animals to humans.[37]

CC398 is a methicillin-resistant Staphylococcus aureus which was produced by the use of antibiotics in livestock production.[38]

The appearance of Carbapenem resistant enterobacteriaceae has been attributed in part to antibiotic use in livestock.[39]

Mechanisms for transfer to humans[edit]

There is evidence that a large proportion of resistant E. coli isolates causing blood stream infections in people are from livestock produced as food.[40]

When manure from antibiotic-fed swine is used as fertilizer elsewhere, the manure may be contaminated with bacteria which can infect humans.[41]

Action and advocacy by country[edit]

Legislation and activism worldwide have aimed at restricting antibiotic use in livestock.

European Union[edit]

On 1 January 2006 the European Union banned the non-medicinal use of antibiotics in livestock production.[42]

United States[edit]

Some grocery stores have policies about voluntarily not selling meat produced by using antibiotics to stimulate growth. 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.[43]

The U.S. Animal Drug User Fee Act was passed by Congress in 2008 and requires that drug manufacturers report all sales of antibiotics into the food animal production industry.[44][45]

Some proposed legislation in the US has failed to be adopted.[46] The Animal Drug and Animal Generic Drug User Fee Reauthorization Act of 2013 proposes other regulation.

In the United States the danger of emergence of antibiotic-resistant bacterial strains due to wide use of antibiotics to promote weight gain in livestock was determined by the United States Food and Drug Administration in 1977, but nothing effective was done to prevent the practice. 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 which violated FDA regulations.[47] On 11 April 2012 the FDA announced a program to phase out unsupervised use of drugs as feed additives and, on a voluntary basis, convert approved uses for antibiotics to therapeutic use only, requiring veterinarian supervision of their use and a prescription.[48][49]

China[edit]

In 2012 an American newspaper described the Chinese government's regulation of antibiotics in livestock production as "weak".[50]

India[edit]

In 2011 the Indian government proposed a "National policy for containment of antimicrobial resistance".[51] 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.[52][53]

Brazil[edit]

Antibiotic resistant bacteria have been found in Brazilian cattle.[54]

South Korea[edit]

In 1998 some researchers reported use in livestock production was a factor in the high prevalence of antibiotic resistant bacteria in Korea.[55] In 2007 The Korea Times noted that Korea has relatively high usage of antibiotics in livestock production.[56] In 2011 the Korean government banned the use of antibiotics as growth promoters in livestock.[57]

New Zealand[edit]

In 1999 the New Zealand government issued a statement that they would not then ban the use of antibiotics in livestock production.[58] In 2007 ABC Online reported on antibiotic use in chicken production in New Zealand.[59]

References[edit]

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    • "Boycott on Meat is Rapidly Spreading; Men Who Are Blamed For High Price", Atlanta Constitution, January 25, 1910, p1
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External links[edit]