Residual Antibiotics in Food


All animals are subject to bacterial infections from time to time. Most infections can be treated with a simple injection. But there are an increasing number of bacteria developing a resistance to common drugs. This has many consumers and food safety agencies, like the CDC, worried that antibiotic-resistant bacteria can begin infecting humans. Answering this concern, many consumers are opting for organic foods which are produced without using antibiotics. And some restaurants are now offering organic meal options to meet this increasing demand.

Antibiotic Residue

When humans and animals are injected with antibiotics, the drugs accumulate in the body. These accumulated drugs are called antibiotic residue. Antibiotic residue is detectable in the blood, muscle tissue and body fluids, like milk. After the animal is taken off the antibiotics, the drug residue eventually passes out of their system. There are tests to determine the level of antibiotic residue present in the animal’s system. High residue levels will signal the farmer to withhold that animal’s product from the market for a longer period of time.

Manufacturing facilities are also subject to annual audits to assure that the production processes and materials used still conform to NSF standards.

The big question for both sides of the argument is how much antibiotic residue is too much? Some claim that any amount of antibiotic residue is too much and will cause bacteria to mutate and become drug resistant in both humans and animals. But those who use antibiotics in livestock argue that current tests are sensitive enough, and can detect any residue present, even at levels that are too low to cause any concern.

Of course, when purchasing meat and dairy products to use in restaurant meals, the argument always comes down to money. Organic farmers do not use antibiotics, so there will be no residue. But organic foods yield less and therefore cost more. It is important to judge your customer base and determine if providing organic meal options will bring more clients through the door. Usually customers who choose to go organic are willing to pay the extra cost.

(The actual amount of antibiotics being used on animals in the United States is not available to either the government or the public. But the Animal Health Institute estimates that 20.2 million pounds of antibiotics were used on livestock and pets in 2003.)

Purpose for Antibiotic Use in Food Animals

Food-producing animals are given antibiotics for three different reasons.

  • Fight disease. Antibiotics are used to kill bacteria in sick animals and make them healthy again.
  • Prevent disease. Much like a human flu shot, animals that are considered healthy are often given antibiotics during times of the year when they may become susceptible to disease.
  • Promote growth. Low doses of antibiotics are sometimes added to cattle, poultry and swine feed to increase their body size.


Withdrawal Period

All food animals that are injected with antibiotics must go through a withdrawal period before the meat or milk can be shipped to the market. A withdrawal period is the amount of time it takes any antibiotic residue to be flushed out of the animal’s system, enough that it will not show up on standard tests. All of the antibiotics are labeled with the appropriate withdrawal period. Whether it is hours, days or weeks, withdrawal periods vary per drug.

Manufacturing facilities are also subject to annual audits to assure that the production processes and materials used still conform to NSF standards.

Typically, during the withdrawal period, a dairy farmer simply milks an injected cow last and dumps her milk down the drain, so the antibiotic-laden milk does not contaminate the entire supply. Meat producers just have to withhold sending an injected animal to slaughter until the withdrawal period is over.

Source of the Controversy

Conventional farmers say they need to use antibiotics to keep their animals healthy and productive. Farmers also state that antibiotic tests are so sensitive that any residual antibiotics are at levels too low to be harmful to humans. Opponents of antibiotics fear that even trace amounts are causing antibiotic resistant germs that can threaten human health.

(In the summer of 2007, the FDA halted imports of several fish species raised in China after detecting residues of a banned antibiotic and three cancer-causing antimicrobials, also banned in the United States. News reports like this help fuel the debate against antibiotic use in food-producing animals.)


Arguments for Antibiotics

  • Antibiotics keep the animals healthy. The primary reason for using antibiotics is to prevent and fight diseases. Without their use, many food animals would die, putting more strain on food prices. » Learn More
  • The antibiotics are not harmful to humans. One of the most common antibiotics used is penicillin. This antibiotic is also used to fight common infections in human as well, so residual penicillin poses little threat to human health.
  • Residue tests are sensitive enough to assure safety. If milk from a single dairy cow is contaminated with antibiotic residue (one dairy cow can average eight gallons of milk a day), standard tests are able to detect that residue in 64,000 gallons of milk.1 With this level of sensitivity, antibiotics that are detected are often at levels too low to cause concern.
  • There is no profit in being caught. Before milk or meat is made available to the public, it is tested for antibiotic residue. If even a trace amount is located, the responsible farmer has to pay for all subsequent contamination. For example, if a dairy farmer was found responsible for contaminating an entire truckload of milk (worth approximately $10,000 or one month’s income for a small dairy farmer) 2 ; the milk hauler makes the farmer pay for the entire shipment. The farmer is even responsible for disposing of the tainted milk. So no farmer would risk a month’s income through carelessness.


Argument Against Antibiotics

  • Antibiotic resistant pathogens are increasing. Two of the most common bacteria responsible for foodborne illnesses are Salmonella and Campylobacter. But the rate at which resistant strains are evolving is increasing to the point that many doctors are no longer prescribing antibiotics to treat most cases.
  • Antibiotics kill helpful bacteria. Humans and animals naturally have helpful bacteria in their intestines. These bacteria usually keep harmful pathogens in check when ingested. But if a person takes an antibiotic that inadvertently kills off helpful bacteria, the few remaining harmful bacteria can cause illness.
  • The food supply may be a source of resistant genes. It does not take harmful bacteria that are antibiotic resistant to pose a threat. If humans ingest helpful bacteria that are resistant, those resistance genes can be passed to disease-causing bacteria that will reproduce and spread.


What the Government has to Say

Currently, government regulations in the United States still allow antibiotic use in food-producing animals. Dosage and withdrawal periods are clearly labeled on all drugs, so as long as those are strictly followed, no harmful amount of antibiotic residue should enter the food supply. But the CDC is tracking antibiotic-resistant strains and recognizes it as an increasing concern for human health.

Also, the World Health Organization has determined that using antibiotics to promote animal growth is the leading cause of bacterial resistance. The WHO recommends that antibiotics not be used for this purpose out of concern for public health and well-being.

1 John Rahm (Owner/Operator, Daisy Lane Registered Jerseys), in discussion with the author, October 17, 2008.
2 Ibid.

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