Feeding antibiotics to livestock creates an ever-increasing number of resistant bacteria, including many that can harm humans
A recent study from the Maryland School of Public Health has found a simple way to help overcome the health problems caused by antibiotic resistance: stop adding antibiotics to animal feed. The study found that when poultry and beef are produced without these antibiotics, bacterial resistance quickly declines.
Feeding antibiotics to livestock creates an ever-increasing number of antibiotic-resistant bacteria, including many that cause disease in humans. Yet up to now, no one has been able to say how quickly the damage can be undone by ending this practice or if it can be undone at all.
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The study, by a team that included researchers from Pennsylvania State University and Johns Hopkins Bloomberg School of Public Health as well as the Maryland School of Public Health, found an immediate and substantial decrease in antibiotic-resistant bacteria on poultry farms that had just switched from conventional to organic practices. (1) And this happened in the very first flock raised organically.
"While we know that the dynamics of antibiotic resistance differ by bacterium and antibiotic, these findings show that, at least in the case of enterococci, we begin to reverse resistance on farms even among the first group of animals that are grown without antibiotics," said lead researcher Amy R. Sapkota, an assistant professor with the Maryland Institute for Applied Environmental Health in a university press release.
But this study's findings won't become reality on their own. Meat and poultry farmers must embrace it. For that to happen, consumers will have to persuade them through the power of the pocketbook.
Over Half a Century of Antibiotics in Animal Feed
Including antibiotics in animal feed became routine soon after the rise of feedlots. Meat animals are fed antibiotics because doing so increases their weight and makes meat production cheaper. As far back as 1946, it was known that healthy animals fed low doses of antibiotics -- doses strong enough to kill some of the animals' internal bacteria but not all of them -- grew to market weight on less feed than animals that weren't fed antibiotics.
"You start giving [cattle] antibiotics, because as soon as you give them corn, you've disturbed their digestion, and they're apt to get sick, so you then have to give them drugs, says Michael Pollan, author of In Defense of Food: An Eater's Manifesto. "That's how you get in this whole cycle of drugs and meat.... Once they start eating the [corn], they're more vulnerable. They're stressed, so they're more vulnerable to all the different diseases cows get." (2)
Because of this, meat animals are also fed antibiotics protectively, to prevent the spread of disease before disease even occurs. Meat animals are raised under highly crowded conditions, which means that on the typical meat or poultry farm, one sick animal can easily infect all the others. This is similar to what occurs with people living in overcrowded conditions, where disease rates traditionally soar.
All these antibiotics add up. The Union of Concerned scientists estimated that 70 percent of all antibiotics in the U.S. (24.6 million pounds annually) are fed to healthy livestock, not taken by people. (3)
When antibiotics are fed to farm animals, even at the low levels used to aid growth, the remaining bacteria within the animals tend to acquire resistance to them. This was seen as early as 1951 in streptomycin-fed turkeys. (4) But it didn't set off many alarm bells. The main impact of antibiotic resistance is seen in infections in humans, but back in the 1950s an infection that couldn't be cured with streptomycin could still be cured by using penicillin or some other antibiotic. But that was about to change.
The Spread of Antibiotic Resistance
Bacteria spread antibiotic resistance to other bacteria, even bacteria of a different species, by genetic transfer. This means that a harmless intestinal bacterium could make a disease-causing bacterium antibiotic resistant. Sewers are excellent breeding grounds for such transfer. This began to set off the alarm bells. But it wasn't until the advent of methicillin-resistant Staphylococcus aureus -- MRSA -- that the alarm bells really began ringing.
(1) Sapotka AR, Hulet RM, Zhang G, et al. Lower Prevalence of Antibiotic-resistant Enterococci On U.S. Conventional Poultry Farms That Transitioned to Organic Practices. Environmental Health Perspectives, Aug 10, 2011. Published online ahead of print. http://dx.doi.org/10.1289/ehp.1003350 Last accessed September 10, 2011.
(2) PBS interview with Michael Pollan, part of the Frontline show, "Modern Meat" http://www.pbs.org/wgbh/pages/frontline/shows/meat/interviews/pollan.html Last accessed Sept 10, 2011.
(3) Mellon M, Benbrook C, and Benbrook KL. Hogging it: Estimates of Antimicrobial Abuse in Livestock. January 2001. Union of Concerned Scientists website http://www.ucsusa.org/assets/documents/food_and_agriculture/hog_front.pdf Last accessed September 10, 2011.
(4) Starr MP and Reynolds DM. Streptomycin resistance of coliform bacteria from turkeys fed streptomycin. Proceedings of the 51st General Meeting, Society of American Bacteriology, Chicago, IL. 1951:15-34.