How Do Factory Farms Use Antibiotics?

Antibiotic resistance is a major global public health crisis.  Over 1.2 million people have died from infections resulting from antibiotic-resistant bacteria, with the number of casualties projected to increase by millions in the coming decades. One of the major drivers of antibiotic resistance is livestock farming. Animals are kept in crowded and often unhygienic conditions that encourage disease, and as a result farms resort to the excessive use of antibiotics to control infection. 

How Much Antibiotics Does the Factory Farming Industry Use per Year?

The FDA reports that over 6 million kilograms of medically important antibiotics were used in the U.S. in 2020, down from a historic peak in 2015, but an increase since 2017. Worldwide, It’s estimated that roughly 73 percent of all medically important antibiotics are used in animal agriculture. Analysis suggests that global antibiotic use is set to continue to grow through at least 2030. Instead of being used to treat diseases, most of these antibiotics go toward preventing disease and increasing productivity. 

The heavy use of these antibiotics in animals is driving the global rise of antibiotic-resistant bacteria, which are causing diseases that killed over a million people worldwide in 2019, and are responsible for more than 35,000 deaths in the U.S. every year. 

How Are Antibiotics Used in Factory Farming?

According to the FDA, more than half of the antibiotics used on farms in 2020 were medically important antibiotics — also used to treat humans — used by livestock producers to prevent disease and encourage productivity. 

New rules from the FDA preventing the use of antibiotics solely to encourage growth in livestock went into effect in 2017, yet use of these drugs on farms remains at a high level. Antibiotics are generally necessary on factory farms to counteract the severe health impacts that stem from living in crowded and dirty conditions. Meanwhile, in the EU antibiotics for the purpose of “compensating for inadequate husbandry or poor hygiene” is illegal. 

Which Antibiotics Do Farmers Use?

Most of the antibiotics used on factory farms in the U.S. are medically important. Of the 11 antibiotics that were reported to the FDA as being used in livestock in 2020, nine are medically important. 

• Aminoglycosides. Originally introduced for clinical use in 1944, these drugs lost favor with medical professionals in the 1980s as doctors began to turn to newer antibiotics that were considered safer. However, increasing antibiotic resistance to these new drugs has caused a renewed interest in aminoglycosides. Examples of medications in this class include gentamicin and tobramycin. For livestock, the drugs are mostly used to prevent disease. 
• Amphenicols. Amphenicols, which are medically important, include drugs such as chloramphenicol and florfenicol. These drugs are used for farm animals relatively infrequently. According to the FDA, in 2020 just under 52,000 kilograms of these drugs were used for livestock. 
• Cephalosporins. Cephalexin and cefazolin are cephalosporins. The drugs in this family are frequently used to treat meningitis, skin and other infections. Since 2011, the use of these drugs for animals has decreased slightly, though in 2020 26,262 kilograms were administered to livestock and other animals. 
• Fluoroquinolones. There are numerous important antibiotics that fall under the classification of fluoroquinolones, including levofloxacin and ciprofloxacin. These medications are often used to treat pneumonia, gastroenteritis and urinary tract infections. 
• Lincosamides. There is only one drug in this class that is used clinically, clindamycin. Uses include treating vaginosis, skin infections and respiratory infections. Just over 147,000 kilograms were used for animals in 2020. 
• Macrolides. Azithromycin and erythromycin are two of the drugs in the macrolides family. They can be used to treat pneumonia, tonsillitis and middle ear infections. They accounted for more than 430,000 kilograms, or 7 percent, of the medically important antibiotics used in farmed animals in 2020. 
• Penicillins. Drugs in the penicillin class are some of the most commonly prescribed antibiotics. Among them are penicillin G and amoxicillin. They can be used to treat urinary tract infections, ear infections and dental infections, among other ailments. More than 762,000 kilograms of the drugs were used for animals in 2020. 
• Sulfonamides. These medically important antibiotics are also known as “sulfa drugs.” Included in the group are zonagram and sulfisoxazole. In 2020, these drugs made up 3 percent of all antibiotics used for farm animals. They can be used to treat urinary tract infections, eye infections and even bowel disease. 
• Tetracyclines. Two examples of tetracyclines are doxycycline and minocycline. This group of medically important antibiotics can be used to treat a variety of infections and even acne, though they are ineffective against viral infections. They are the most heavily used medically important antibiotics within animal agriculture, accounting for 38 percent of all antibiotics given to animals. Almost 4 million kilograms were used in 2020. 

There are only two groups of antibiotics that are not considered medically important that are used heavily within animal agriculture. 

• Ionophores. This class of drugs — which includes monensin and narasin — makes up 35 percent of all antimicrobial drugs used in animals. In 2020, just over 3.6 million kgs of these drugs were given to farm animals. 
• Pleuromutilins. Retapamulin and valnemulin are two of the drugs in this family. Collectively, they made up 2 percent of all antibiotics given to livestock in 2020. 

Why Are Antibiotics Used in Farming?

Antibiotics are used in farming for two primary reasons: to increase efficiency and prevent disease. These two motives are connected, because disease spread can also have a large impact on productivity and efficiency. Although it is viral rather than bacterial, the ongoing avian flu pandemic is one such example. Entire flocks are killed once disease exposure is suspected.

Increasing Efficiency

Although giving antibiotics to livestock for the sole purpose of increasing growth is technically illegal in the U.S., the same antibiotics are often given as disease prevention in similar dosages and for similar time periods. 

Preventing Disease Spread

Livestock production systems are breeding grounds for disease. That’s why antibiotics are used to prevent disease from spreading, even in animal populations that show no signs of illness. 

How Do Factory Farms Spread Treatment-Resistant Bacteria?

As was the case with Staphylococcus aureus, a bacteria that causes everything from minor skin infections to lethal blood infections, bacteria can spread from people who work on factory farms to animals and vice versa. Resistant bacteria spreads in the same way, often spreading in pathogens. Once enough resistant bacteria accumulates in a person or animal, antibiotics will no longer be effective at treating disease in that individual. 

Should Antibiotics Be Used in Farming?

The primary reason that most antibiotics are used on factory farms is to compensate for a lack of hygiene and welfare. Given both the public health and animal welfare consequences of continuing to routinely administer antibiotics en masse to livestock, public health experts urge reduced or eliminated use of antibiotics for those reasons, recommending that they be used only when necessary to treat sick animals.  

Antibiotic Use in Agriculture by Country

Antibiotic use varies by country. Brazil, China and the United States currently use the most antibiotics in livestock farming. However, the practice is projected to increase in several other countries as industrial agriculture continues to grow. These countries include Myanmar, Indonesia, Nigeria, Peru and Vietnam. 

What Effect Will Giving Antibiotics to Animals Have on the People Who Eat Those Animals?

There are a variety of ways that giving antibiotics to animals can impact people. One risk is that there will be antibiotic residue in meat, though the risk is small in places with withdrawal periods before slaughter, during which time antibiotics cannot be given. 

Another risk associated with giving antibiotics to livestock is that some of the resistant bacteria will be introduced directly to the consumer. However, if food is properly cooked the chances of this happening are minimal. 

How Does Factory Farming Contribute to Antibiotic Resistance?

Every single time that an antibiotic is administered, whether to humans or animals, there is always some drug-resistant bacteria that remains in the body. The more that resistant bacteria is allowed to flourish the more it will spread — it’s also found in soil and water on farms, spreading easily between animals and humans. Factory farming contributes to the problem of antibiotic resistance due to the sheer quantity of antibiotics administered to farm animals. 

Antibiotic Resistance

Administering antibiotics in the food and water of livestock, whether they are ill or not, is routine practice on factory farms. This provides an opportunity for resistant bacteria to spread to staff or those who consume the meat if residue is still detected. 

Antibiotics and the Environment

The role that the environment plays in spreading antibiotic-resistant bacteria is not fully understood. However, what researchers have discovered is that antibiotic-resistant bacteria are present in the natural environment, including in the soil and water. The bacteria comes from a number of sources, including human and animal waste. 

Public Health Threat

Antibiotic resistance has been acknowledged as a public health threat by experts around the world. The World Health Organization calls it “one of the biggest threats to global health, food security, and developments today.” As the situation worsens, a variety of infections are becoming increasingly difficult to treat, leading to a steadily increasing number of casualties. 

What You Can Do

Antibiotic resistance is a serious threat to global public health. Reducing meat consumption by shifting to a plant-rich diet is one way to help, as well as supporting public health advocacy groups. You can also donate to projects such as Transfarmation that seek to transition farmers out of raising livestock. If you’re a teacher or other educator, consider scheduling a presentation from Factory Farming Awareness Coalition, an organization that exists to educate students about the impacts of factory farming.