How CAFOs Contribute to Antibiotic Resistance

Antibiotic Resistance Resources

The rise in public concern about antibiotic resistant bacteria in the environment could well be the Achilles’ heel of industrial livestock operations or factory farms. The association of antibiotic resistant bacteria with the routine feeding of antibiotics to livestock and poultry in large-scale confinement operations has been known by animal scientists since at least the 1970s. The problem of disease outbreaks discouraged the widespread crowding of animals into confinement buildings until animal scientists discovered that routine use of antibiotics could suppress diseases to a manageable level. The discovery that low-levels of antibiotics in feed also increased feeding efficiency, resulting in faster animal growth, was an economic bonus for the owner.

70-80% of all antibiotics in US are used in industrial livestock production.

Routine feeding of antibiotics at sub-therapeutic (low dose) levels provides an ideal breeding ground for antibiotic resistant organisms, such as the deadly methicillin-resistant Staphylococcus aureus (MRSA), which killed more than 18,000 people in 2008 – more than AIDS. The low doses are not sufficient to eradicate all the bacteria, and those that survive change their genetic make-up in response to the antibiotic.. They then multiply rapidly to generate a new population of bacteria that are antibiotic-resistant..

Since many human diseases were transmitted from farm animals to humans, it is not surprising that many antibiotics that are widely used to treat humans are effective for animal diseases. Prior to routine antibiotic feeding to animals, antibiotic resistance was generally linked to misuse of antibiotics in hospitals or by individual patients of private physicians. While misuse is still a logical source of antibiotic resistance, scientific evidence is mounting that links antibiotic resistant bacteria in humans with routine feeding of antibiotics to livestock in confinement facilities.

With the advent of factory farms, livestock producers quickly became a major user of antibiotics in the United States. An estimated 70-80% of all antibiotics in the U.S. are used in industrial agriculture. The majority of antibiotics are fed at sub-therapeutic (low dose) levels for disease prevention and growth stimulation. A comprehensive 2004 U.S. General Accounting Office review of the scientific literature on antibiotic resistance clearly linked antibiotic resistance to livestock feed. They reported that “many studies have found that the use of antibiotics in animals poses significant risks for human health, but a small number of studies contend that the health risks of the transference are minimal.”[1]

By 2013, a U.S. Center for Disease Control and Prevention report concluded that any doubt about the potential for transference of antibiotic resistant bacteria from animals to humans had been resolved: “Scientists around the world have provided strong evidence that antibiotic use in food-producing animals can harm public health through the following sequence of events: Use of antibiotics in food-producing animals allows antibiotic-resistant bacteria to thrive while susceptible bacteria are suppressed or die. Resistant bacteria can be transmitted from food-producing animals to humans through the food supply. Resistant bacteria can cause infections in humans. Infections caused by resistant bacteria can result in adverse health consequences for humans.”[2] The evidence is clear that antibiotic resistant bacteria is a major risk to public health, and it is clearly linked to factory farms.

1) U.S. Government Accounting Office report to congressional requestors, “ANTIBIOTIC RESISTANCE Federal Agencies Need to Better Focus Efforts to Address Risk to Humans from Antibiotic Use in Animals,” April 2004, .

2) US Center for Disease Control and Prevention, ANTIBIOTIC RESISTANCE THREATS IN THE UNITED STATES, 2013 Executive Summary, .

Antibiotic Resistance Resources used with permission from Iowa Alliance for Responsible Agriculture.