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Chicken Antibiotics: Why Are Chickens Given Antibiotics?

April 27, 2022

A variety of antibiotics are routinely given to chickens on factory farms, which can disastrous results for humans.

A patient’s organs start shutting down at the hospital. She’s confused and has a fever. Eventually, she’s intubated because her body cannot breathe on its own. In a viral YouTube video, we learn that the patient, JC, was infected with deadly bacteria at the site of her intravenous fluid injection. The antibiotic-resistant bacteria were transferred from the bed of a nearby patient, and JC experienced sepsis as a result of the bacteria entering her blood. 

Bacteria are small single-celled organisms and many live on the surface of your skin—mostly good, some bad. Without practicing good hygiene like hand-washing,, we could be spreading deadly bacteria unknowingly. Bacterial infections used to be the primary cause of death, killing more people than heart attacks, cancer, or strokes. As doctors began to understand bacteria, they changed how they practiced medicine. As a result, we now understand how important it is to keep medical tools and surfaces clean in hospital surgery rooms in order to prevent the spread of diseases and infections.

Antibiotics have become a central part of our modern medical system, allowing people to perform surgeries and other procedures that would be impossible without these drugs. Antibiotics kill most bacteria, but overuse can lead to some bacteria resisting antibiotics and forming stronger populations, or mutating and gaining resistance. The bacteria that nearly killed JC was MRSA, a drug-resistant “superbug” that has become common in hospitals in the last few decades. Each year in the United States alone, superbugs cause 2.8 million nonlethal infections such as the one that JC experienced, yet there is a lot we can do to fight against the rise of superbugs.

Antibiotics should be a last resort, but they've come to be viewed as a wonder drug and used with little restraint. Factory farms around the world have been using antibiotics as a first resort for decades—as growth promoters and  to prevent animals from succumbing to diseases that  are more readily transmitted in confined animal feed operations.  . Farmed animals raised for their meat—such as chickens, pigs, and cows—live in crowded and dirty conditions that are perfect for spreading harmful bacteria. Rather than improve the living conditions of farmed animals, which can be expensive, farmers use antibiotics instead. Nearly two-thirds of all the medically important antibiotics used in the United States are fed to nonhuman animals. Only 2 percent of the antibiotics used in agriculture, however, are given to chickens, while the majority goes to cows and pigs

Are Antibiotics Given to Chickens?    

Antibiotics are given to all farmed animals, including chickens. However, a 2020 report indicates that only 1 percent of broiler chickens are raised on full-spectrum antibiotics, and half are raised without any use of antibiotics at all.

In the past decade, environmental  groups such as Natural Resources Defense Council (NRDC) and their allies have worked to convince U.S. food companies to stop selling chicken meat from farms that rely on antibiotics for routine use (instead of for disease treatment). Companies like McDonald’s, Subway, KFC, Chick-Fil-A, Chipotle, Panera and other major buyers of chicken, and even Foster Farms, a major chicken producer, have committed to reducing their use of antibiotics, all because of successful advocacy. This change in the chicken industry is one that advocates are continuing to press for in other industries like beef and pork where antibiotic use has continued to rise 

Are Antibiotics Legal in Chicken?

Yes, it is legal to feed antibiotics to chicken. In 2017, the United States Food and Drug Administration (FDA) issued rules to ban the use of antibiotics for growth promotion. The European Union’s European Medicines Agency (EMA) had already banned the use of antibiotics for growth promotion in 2005. Between 2011 and 2020, European farmers reduced their use of antibiotics by 43 percent. 

Instead of admitting to using antibiotics for growth promotion, however, chicken producers can say that they are preventing diseases—and continue routinely feeding antibiotics to their flocks. To close this loophole, the EMA is expected to ban the use of antibiotics for preventive use in 2022. 

Why Are Chickens Given Antibiotics?    

Chickens are given antibiotics to help their bodies fight back against diseases. Farmed chickens live in overcrowded conditions that are hard to keep clean and where it’s easy for the birds to spread harmful bacteria. Antibiotics are seen as a low-cost, immediate way to stop chickens from getting sick or sicker. This view is increasingly outdated, however, and chicken producers have led the way within the meat industry in significantly reducing antibiotics use from 2016 to 2020. Unfortunately, antibiotic use has increased in other animal industries, despite the new rules against growth promotion.

Which Antibiotics Are Used on Chickens?    

The following list includes categories, or classes, of antibiotics that are used for  chickens and other farmed animals. Except for ionophores, all of these drugs are also used to fight human illness. This means that if the use of these drugs on farms leads to antibiotic-resistant bacteria, the drugs become less useful in human medicine as well. Advocates for the environment, farmworkers, public health, and animals agree that antibiotics should be reserved for treating diseases, and not routinely fed to factory-farmed animals to prevent them from becoming sick in the intensively-confined conditions..

Aminoglycosides: Treat Intestinal Infections

Aminoglycosides are considered critically important medicine to humans. Not only are they used for chickens and other animals, they are also used as a pesticide among citrus growers in California and Florida. 

Bambermycins: Prevent the Synthesis of the Cell Walls of Bacteria

Bambermycins were banned in Europe in 2006, but remain permitted in the United States. In “Big Chicken,” Maryn McKenna documents their use in the 2000s via Craig Watts, a chicken farmer she met with in North Carolina who shared with her the receipts containing chicken feed nutrient information for the flocks he raised.

Ionophores: Prevent Intestinal Infections

Except for one version called nystatin, which treats fungal infections, ionophores are not used in humans. In other words, as the FDA reported in 2020, ionophores are not medically important. Ionophores replaced bambermycins on Craig Watts’ timeline of receipts in the 2000s, which seemed to indicate an attempt within the chicken industry to manage antibiotic resistance. Ionophores have not been found to lead to antibiotic resistance, except against bacitracin, an antibiotic that is used in first-aid ointments in the U.S.  

Beta-Lactams: Penicillins and Cephalosporins

Beta-lactam antibiotics include penicillin and cephalosporins. Cephalosporins were originally developed in response to early waves of resistance to penicillin in the mid-20th century. 

Maryn McKenna features cephalosporins in a story about Danish poultry farmers. Even though they had stopped using cephalosporins for a decade, they were still seeing E. coli resistance to the drug. It turned out that their chickens’ ancestors had been hatched in Scotland, where cephalosporin use was allowed. The Danish chickens were still passing on drug-resistant E. coli to each new generation of chickens. 

Lincosamides: Combat Joint and Bone Infections

Lincosamides are used in animal agriculture to treat birds and pigs. Doctors also prescribe the drug to humans for bacterial infections. Antibiotics from this class of drugs are considered highly important in treating humans experiencing toxic shock syndrome. Another use for lincosamides is to treat dental infections in humans. 

Macrolides: Treat a Fatal Condition called Necrotic Enteritis, Which Is Caused by Overeating

Macrolides are considered critical to human medicine. Doctors use macrolides to treat Campylobacter and respiratory infections like pneumonia. Macrolides such as azithromycin (e.g., Zithromax or Z-pak), are also used to treat sexually-transmitted diseases,severe gut infections, and a myriad of other infections in humans. Meanwhile, chickens, pigs, and cows are allowed to receive unregulated amounts of macrolides in the United States for disease prevention. 

Quinolones: Broad-Spectrum Drugs That Affect a Wide Range of Bacteria

Quinolones are a type of antibiotic that includes fluoroquinolone, a medically important drug for humans. Antibiotics can be classified as narrow- or broad-spectrum, depending on how many microorganisms they kill. Fluoroquinolone is a broad-spectrum antibiotic. Medical doctors give fluoroquinolones to patients seeking treatment for pneumonia, urinary tract infections, and severe gut infections. 

In chickens, fluoroquinolone is used to treat respiratory infections. These infections occur because of the high level of ammonia in chicken houses. Chickens live on top of composted litter, meaning that their houses are never cleaned of their droppings the whole time that they are alive, leading to the build up of ammonia.

Streptogramins: Prevent Cell Wall Formation and Protein Synthesis, Used to Treat and Prevent Necrotic Enteritis

Streptogramins are used to treat cows, birds, and pigs. They’re also used for humans who suffer from superbug infections, including skin and soft tissue infections. For humans, this highly important antibiotic is used to treat urinary tract infections, heart infections, and infections from antibiotic-resistant bacteria like Enterococcus and methicillin-resistant Staphylococcus aureus (MRSA).

Sulfonamides: Prevent and Combat Salmonella, E. coli, and Other Pathogens

Sulfonamides are one of two antibiotic classes that, when used in combination, are considered critically important to treating urinary tract infections and foodborne illnesses in humans. They are also approved as a preventative health measure for cows, pigs and chickens.

What Do Antibiotics Do to the Chickens?    

Antibiotics have been used in the past to help chickens grow faster so farms can slaughter them and bring their meat to market quicker. With the banning of antibiotic use for growth promotion, chickens are now fed antibiotics for preventive health purposes or to treat a specific ailment. For example, ionophores help prevent coccidiosis, a potentially fatal disease that inflames the bird’s intestines. Coccidiosis is common in overcrowded poultry houses, and ionophores are used in European and American chicken farms to combat this disease. 

Consumer Health Effects of Chicken Antibiotics  

Antibiotic-resistant strains of bacteria in chicken can lead to food-borne illnesses. About 1 in 6 salmonella infections and about 1 in 3 campylobacter infections are due to antibiotic-resistant strains of those bacteria. The consumption of chicken and turkey is the source of two-thirds of campylobacter infections and one-fifth of salmonella infections in the United States.

Current U.S. Federal Regulators    

Regulation of the use of antibiotics in meat production is weak in the United States. It’s so weak that advocates have targeted slaughterhouses to push for requiring vaccinations and probiotics for birds as a way of curbing the overuse of antibiotics in the meat industry. 

Other suggestions advocates have made for reform include requiring slaughterhouses to test more chickens and reject birds carrying dangerous bacteria. At the slaughterhouses, better hygiene practices could be implemented, including sterilizing defeathering machines and conveyor belts. Reforms like this have been difficult to achieve due to the limited resources of the USDA and influence of lobbyists for the animal agriculture industry  on regulatory policies.

How Does USDA Operate?

The U.S. Department of Agriculture has limited oversight of chicken farms and hatcheries. Its Animal and Plant Health Inspection Service can take measures to promote animal health, but its power is limited to making farmers vaccinate their hens against specific strains of salmonella. The same is true of the Food Safety Inspection Service’s role in ensuring meat safety at the processing plant. While there is potential for more leadership in regulating the use of antibiotics in chickens, some of the most effective actions have not been taken.. For example, the USDA could decide to withhold their “USDA Inspected” seal to any processing plant, which would make it illegal to sell their chicken. Meanwhile, the USDA is not able to issue recalls—that is something that companies must do voluntarily.  

How Does the FDA Regulate the Use of Chicken Antibiotics?

The Food and Drug Administration (FDA), a division within the U.S. Department of Health and Human Services, issued rules to ban the use of antibiotics for growth promotion in 2017. However, it preserved the use of antibiotics for preventive care, which is allowing the continued excessive use of the drugs. David Wallinga of the NRDC insists that the FDA is not doing enough to regulate the use of antibiotics in chickens and other farmed animals. For example, the FDA is reporting sales of antibiotics but there is no data on how the antibiotics are actually used in farms. 

There is some overlap between how the USDA and the FDA regulate the U.S. food supply, the nuances of which are beyond the scope of this article. In terms of the chicken industry the USDA regulates meat, poultry, and egg products, while the FDA regulates “whole eggs in the shell.”

What Does the CDC Say About Antibiotic Resistance?

The U.S. Centers for Disease Control and Prevention (CDC), part of the U.S. Department of Health and Human Services, has called antibiotic resistance one of the world’s most pressing health problems. In a comprehensive report on the topic in 2019, the CDC reported that efforts taken in the U.S. to prevent antibiotic resistance since 2013—in the context of human, animal, and environmental health—have been successful. There has been a decrease in deaths from antibiotic resistance in and outside of hospital settings in the U.S., despite a rising death toll from antibiotics worldwide. But there is more to do,  from promoting hand washing to addressing antibiotic overuse.

What Is Antibiotic-Free Chicken?    

According to the Antibiotics Off the Menu Coalition website, antibiotic-free chicken can mean that there are no residues of antibiotics on the actual meat that is sold, which would be illegal. But the problem is the microorganisms that are resistant to antibiotics that may be present on meat, leading to infections.

What Do “No Antibiotics” Claims Really Mean?

The claim of “no antibiotics” can mean different things depending on who is saying it. It does not necessarily mean that a chicken was raised entirely without antibiotics, or that antibiotics were only used according to recommended practices. The Antibiotics Off the Menu Coalition website has a list of third-party-verified labels to look for if you decide to purchase chicken that was raised with responsible antibiotic use. Fortunately there is a plethora of plant-based alternatives to chicken that are becoming more accessible every day, in addition to standard plant-based proteins like beans and tofu. 


The reduction of antibiotic use in the U.S. chicken industry is a promising example of how meat producers and food companies can be pressured by activists to change their practices for public health. The movement to fight antibiotic resistance is global and continues to gain momentum. It unites people whose interests lie in public health, farming, animal advocacy, and environmental justice. While there's still much more to be done, one thing is clear: our collective demand for animal products plays a major role in the proliferation of antibiotic resistant bacteria, and we can help support a shift away from antibiotic-dependent factory farms by choosing plant-based chicken and other plant proteins over chicken, beef, and pork.