The editors of Scientific American recently encouraged U.S. hog farmers to “follow Denmark and stop giving farm animals low-dose antibiotics.” Sixteen years ago, in order to reduce the threat of increased development of antibiotic resistant bacteria in their food system and the environment, Denmark phased in an antibiotic growth promotant ban in food animal production. Guess what? According to Denmark’s Ministry of Food, Agriculture and Fisheries the ban is working and the industry has continued to thrive. The government agency found that Danish livestock and poultry farmers used 37% less antibiotics in 2009 than in 1994, leading to overall reductions of antimicrobial resistance countrywide.

Except for a few early hiccups regarding the methods used in weaning piglets, production levels of livestock and poultry have either stayed the same or increased. So how did Danish producers make this transition, and why isn’t the U.S. jumping to follow suit? Like many things in industrial agriculture, the answer is not clear.

If any country knows how to intensively produce food animals, particularly pigs, it is Denmark. In 2008, farmers produced about 27 million hogs. In fact, the Scandinavian country claims to be the world’s largest exporter of pork.  Thus Scientific American editors argue that the Danish pork production system should serve as a suitable model to compare to ours. U.S. agriculture economists from Iowa State University agree. In a 2003 report, Drs. Helen Jensen and Dermot Hayes stated that Denmark’s pork industry is “…at least as sophisticated as that of the United States… and is therefore a suitable market for evaluating a ban on antibiotic growth promotants (AGPs).”

Based on Denmark’s experience, concerns that an AGP ban in the U.S. would cripple the industry appear to be overblown. A study published last year in the American Journal of Veterinary Medicine by Danish researchers suggested that Denmark’s AGP ban in food animals reduced overall antibiotic use and did not significantly impact production. In fact, recent numbers from Denmark show production levels of hogs increased by roughly 50% between 1992 and 2008.


So what additional changes did Danish hog producers make in their methods of production to ensure that the AGP ban did not negatively affect their bottom line to a significant degree? Robert Martin, Senior Officer of the Pew Environment Group and former Executive Director of the Pew Commission on Industrial Farm Animal Production, visited several Danish hog farms in 2009 to see first hand what producers were doing to compensate for not being able to use antibiotics as growth promoters. Martin listed some of what he describes as the most important changes:


•Switching to lower density models of housing pigs

•The use of open pen & deep bedding systems

•Cleaning barns more frequently and systematically

•Improved ventilation systems

•Improved quality of feed

•Extending weaning period for piglets


Martin explains that many of these changes were phased in as farmers adopted a set of new best practices. Martin says immediately following the ban, Danish producers did see an increase in mortality of young pigs. “But instead of reverting to using antibiotics as a crutch,” Martin continued, “they initiated changes in their system.” For example, Martin learned that many producers extended the piglet weaning times by about 10 days, allowing maternal antibodies in milk to provide increased immunity. Martin also pointed out that reducing the crowded conditions and switching to a dry, deep bedding system, “allowed them to manage waste more effectively.” He said the changes are also “more humane for the pigs.” Moreover, Martin says, “They also paid more attention to feed mixtures instead of relying on antibiotics for weight gain.”


Dr. Jensen and Hayes’s report, published in the Iowa Ag Review, determined a ban similar to Denmark’s could cost the U.S. industry more than $700 million dollars over 10 years and increase the price of pork by about 2 percent at the grocery store. Hayes noted, in recent email exchanges with the Center for a Livable Future, that in the long run a ban would not keep producers from making money. He also wrote, “hog farmers would reduce production until prices recovered, so there is no profit impact.” When it comes to the study’s findings Hayes believes the economics are secondary:


“The key take away for me from our studies was that the ban at the finishing stage worked as planned and reduced antibiotic use by a lot. However, when they extended the ban to the weaning state they ended up using more antibiotics and these were stronger human-use antibiotics. So a ban at the weaning stage did not work in terms of its original intent.”


It is worth noting that recent Denmark data shows weaner mortality is significantly lower since the ISU study was published in 2003. Despite that fact, Hayes is correct. The therapeutic use of antibiotics has increased since the ban was instituted. According to the latest Danish Integrated Antimicrobial Resistance Monitoring and Research Program (DANMAP) report, therapeutic antibiotic use rose by almost 13% from 2008 to 2009. DANMAP also found the occurrence of resistance in Danish pork increased during that time period, “and is not significantly lower than in imported pork.” However, resistance to the antibiotic ciprofloxacin, an important antibiotic in human medicine, was very low in E. coli from Danish pork in contrast to imported pork.  It is important to point out that therapeutic use poses much less antibiotic resistance risk than low-dose application.  Don’t forget, Denmark’s overall antibiotic use in all food animal production remains nearly 40% lower then when the ban was first initiated.


If the AGP ban is, at the very least, reducing overall antibiotic use and Danish pork production levels are increasing why wouldn’t U.S. producers follow suit? The National Pork Producers Council (NPPC) lobbyists publicly maintain they still don’t believe antibiotic use in food animals poses a risk to human health. In a presentation prepared for the World Pork Expo 2010, Chelsea Redalen, the NPPC’s Director of Government Relations, maintained that there is “little to no evidence that restricting or eliminating the use of antimicrobials in food-producing animals would improve human health or reduce the risk of antimicrobial resistance to humans.”


Statements like these, repeatedly made by hog industry representatives, leave many public health experts exasperated.  Numerous peer reviewed research studies including in the U.S. and the Netherlands clearly demonstrate the transmission of antibiotic resistant bacteria from food animals to people. Studies out of the Netherlands published in the Journal of Emerging Infectious Diseases and the Annals of Clinical Microbiology and Antimicrobials, demonstrate that MRSA (Methicillin-resistant Staphylococcus aureus) was transmitted from pigs to a farmer, and between pig farmers and their family.


Despite industry claims, U.S. government health officials have concluded there are direct links between antibiotic use in food animal production and the risk of antibiotic resistant infections in people. Responding to a letter from Drs. Robert Lawrence and Keeve Nachman of the Johns Hopkins Center for a Livable Future (CLF), the director of the U.S. Centers for Disease Control and Prevention, Dr. Thomas Frieden, confirmed that the CDC, “feels there is strong scientific evidence of a link between antibiotic use in food animals and antibiotic resistance in humans.”


CLF helped bring to light recently released FDA data showing that 80% of the antibiotics produced for human and animal use in the U.S. are sold for use in food animals. Even if significant portions of those antibiotics are used to treat disease, Dr. David Love, CLF scientist, says he finds that statistic, “astounding.” Love believes, “if producers are reliant on the use of antibiotics to produce animals in a highly concentrated way, it means that the design of these farms makes them breeding grounds for diseases.” “Even more troubling to me,” Love says, “is the unwise use of antibiotics for growth promotion in animal production, which compromises antibiotics, a precious resource used to protect the public’s health.”


Currently there is proposed federal legislation that would greatly limit antibiotic use in U.S. food animal production. Congresswoman Louise Slaughter (D-NY) recently reintroduced the Preservation of Antibiotics for Medical Treatment Act, better known as PAMTA. The bill would ban the routine use of antibiotics “deemed” critical in human medicine to promote growth in healthy animals.


So, should the U.S. follow Denmark’s lead and stop all food animal producers from dishing out low dose-antibiotics? Public health experts say it appears that those with a higher priority on limiting health risks are at loggerheads with those unwilling to change or corporations more concerned about the risks of increased costs.  One thing is clear – most large pork producers do not plan on instituting a ban voluntarily.



Ralph Loglisci’s “Will the U.S. hog industry ever kick its reliance on low-dose antibiotics?” first appeared in Grist on April 5, 2011 and on Loglisci’s Livable Future Blog on April 6, 2011. Republished with permission.


  • Heh, while you fools are flailing around blindly crucifying hog farms the breaking news is in India.
    Now, that’s how you grow an antibiotic-resistant human pathogen – in humans, not pigs or gerbils or goldfish.
    Scientific illiterates on parade! That’s what happens when Johns Hopkins University sells out to the highest bidder.

  • Steve Gilman

    Once Again, it’s Mr Mud further muddying the waters…. yes, sanitation matters — and antibiotic-resitant cholera and Other resistant strains are very dangerous — wherever they are…
    So — here, this is a preventable problem –why allow antibiotics in animal feed when the dangers to humans are just as real?
    Answer: because that’s the only way the CAFO factory farm system can keep the animals alive and gaining market weight in deplorable crowed conditions… Score another Insane Solution that Creates More Problems for Industrial Ag!

  • Doc Mudd

    Perfect rambling illustration courtesy of organic pitchman Gilman that his and the Johns Hopkins CLF agenda is merely anti-agriculture. It bears no genuine concern or understanding for emergence of antibiotic resistant human pathogens.
    Simply amazing how dreamy dung worshipers like Gilman and career spin journalists like Longlisci have, ready at their fingertips, all the easy answers to complex scientific questions – and those always begin and end by bashing modern agriculture.
    Just one fly in the ointment: with no pigs, no CAFOs involved India has produced the superbug boogieman that Loglisci, Gilman and other blathering alarmists could only conjure up as a fictional possibility.
    Our intrepid amateur faux-pharmacologists are obviously barking up the wrong tree, as it turns out. But then, science and medicine really aren’t their strong suits, are they now? No, fearmongering is their strength – so be afraid, be very afraid!

  • Harvey Cole

    It is time past time to stop the use of antibiotic feed additives.
    I am not against antibiotics. They saved my life once and maybe several times. My Dr. has on occasion prescribed against my will.
    When I had quite extensive second and third degree burns to 23 percent of my body I had to argue and offered to sign off for no prophylactic antibiotics. My reward was came later as others with relative minor burns were ill from lost intestinal flora. I did not have that problem. I did benefit from antibiotics for the bladder infection I received from being catheterized. Then I was glad to get antibiotics.
    I have done many types of surgery and most without antibiotics but I see most of my colleques using antibiotics for prophylaxis.
    As I see it they are selecting the one or 10 bacteria out of the 10 thousand or more bacteria that have the best ability to develop resistance with this unnecessary use of antibiotics.
    My clients are to call me if they have given antibiotics
    without taking the temperature first. I think antibiotics should only be used for treating infection.
    Years ago I saw some research where one of the first experiments
    on adding antibiotics to a feed was flawed. As I remember the animals were in two houses but the antibiotic were given to the animals in the new house and the ones that got no antibiotics
    were in the old house. This experiment kicked off the feed additive theory. Normally the animals in the new clean new
    house would do better even without antibiotics.
    To break even based on information I found in about 1975 based on cost of antibiotics used in prepared feeds they had to produce 2 percent of the gain in all animals involved to just break even economically. I doubt it.

  • Michael Bulger

    Rep. Louise Slaughter reports on her website the her bill would phase out nontherapeutic usage of antibiotics in animals while preserving the right to use antibiotics to treat a sick animal.
    Additionally, the website cites the widespread support of this bill by scientific, medical, and agricultural groups. From the website:
    “Over 300 organizations representing health, consumer, agricultural, environmental, humane and other interests including the American Medical Association, the American Public Health Association, the National Association of County and City Health Officials, and the National Campaign for Sustainable Agriculture, have supported enactment of legislation to phase out non-therapeutic use medically important antibiotics in farm animals.”
    The emergence of antibiotic resistant human pathogens is a fascinating subject. It has been understood for decades that low-doses of antibiotics in livestock feed can spur the development of antibiotic resistant pathogens.

  • Doc Mudd

    I’m certain there are opportunities to employ antibiotic technologies more sensibly and effectively not only in livestock but in humans, as well (the situation in India underscores that). In fact, human use/abuse might reasonably be the highest priority at this time.
    Modern medical science will have to be relied upon to identify and answer meaningful questions, however. Populist opinions contribute nothing to this complex discussion.
    Credentialed medical professionals must be left unmolested to accomplish their best work for our general benefit. That’s unlikely to happen when activist crackpots insist upon corrupting the scientific process and forcing a contrived result in the court of professionally misinformed popular opinion.
    Science is didactic, impartial and unemotional; unbiased by what dopey organized scaremongers and conspiracy theorists circulate in their twisted propaganda. Medical science isn’t a churning democratic process where the emotional masses campaign and vote for their preferred scientific discovery to magically materialize.

  • rbbaker

    The sad news is that most research done in the field with the pigs indicates that low doses of antibiotics – the so called growth promotion or sub-therapeutic levels actually prevent antibiotic resistance more often than they promote it. Any time antibiotics are used there is a risk of resistance development and this is the case for all species especially humans. Bacteria that reside in the gut of an animal are most often involved. Although sub-therapeutic levels of antibiotic use in animal agriculture has been accused as a major issue in the resistance debate, the facts don’t support this assumption. Although it seems to make sense that low doses will cause resistance, that is counter to the highly competitive evolutionary processes that occur in the normal and occasional (pathogens) abnormal bacterial flora which compete in the gut of the pig or other mammal. The bottom line is when a bacteria is under great competitive pressure to survive in its micro-environment thus when it is exposed to antibiotics it must respond or die. To do this, it may mutate, pick up resistance genes from other bacteria or express resistance factors it already possesses. But it does so at a cost which will make it less competitive when the antibiotic is removed. Thus the resistance factor(s) is quickly eliminated when the antibiotic is removed. The removal of antibiotics always happens in modern production due to withdrawal requirements and decreasing marginal value of antibiotic use as the pig grows. Research confirms this process. Treatment especially in human medicine where most resistance arises will select for resistant strains of bacteria if they already exist which is unfortunately common. What happens is the treatment levels kill off the weak non-resistant bacteria and leave the resistant strains to propagate the next generations of bacteria which are now all genetically resistant. Methods of administration and monitoring which minimize resistance are needed in all animals including humans. Most of our methodologies which guide us on resistance determination and antibiotic selection are by modern standards based on ancient and archaic technologies and philosophy. Only science can solve this – picking on animal agriculture is only a distraction that avoids dealing with causation.

  • Doc Mudd

    Thank you, rbbaker for a knowledgeable explanation of complex medical microbiology. The evolution of human pathogens, of quiet killers is a fascinating study requiring science of the highest order. Nicely done.

  • Michael Bulger

    rbbaker, do you have any links or references to scientific articles supporting your statement?
    The literature review I have done into this matter shows nothing to support your claim that pathogens that acquire R+ plasmids and antibiotic resistance are at an evolutionary disadvantage once the antibiotics are removed.
    What you say, “What happens is the treatment levels kill off the weak non-resistant bacteria and leave the resistant strains to propagate the next generations of bacteria which are now all genetically resistant,” is supported in all the studies and reports I’ve read. However, that is making the case that subtherapeutic antibiotics increase the populations of resistant pathogens. That is the position of every medical, scientific, and world body with a published opinion on the matter. If you believe these organizations are incorrect, and assert that the general consensus of medicine and public health is resting on the “ancient and archaic”, it would be helpful if you cited scientific studies.
    Please, rbbaker, provide some reference as to why we should believe you.

  • Bulger apparently missed science class in 6th grade that day the concept of ecological competition was explained. Here’s a simple description, Mike:
    Watch out, rbbaker, you’ve got a junkscience-fueled master’s degree candidate lecturing you on medical microbiology. Be forewarned; Bulger’s sources are painstakingly cherrypicked for their depth…deep in organic fertilzer, that is.

  • Michael Bulger

    I’ll continue waiting for the relevant reference. There is nothing in Mudd’s elementary link that suggests the R+ plasmids render the pathogens “less competitive when the antibiotic is removed”.
    “Ecological competition” is actually a tenet of why low-doses of antibiotics increase resistance frequency. Those that are not resistant, and do not obtain resistance genes from nearby microbes, are killed by the antibiotics. Those that survive are the resistant ones, left with less “ecological competition,” as it is.
    Let’s not expect this “Mudd” to venture from its preconceived notion, though. Science is not important to “Mudd”, just unsubstantiated claims and abuse to those who would actually look at matters with objectivity and a rational eye.
    I will continue to rely on sources… they are better then the zero sources offered by rbbaker.
    For those who would like to learn more, the FDA’s Center for Veterinary Medicine has created an animation to help explain. Further exploration of their website might help illuminate the science that clearly shows that:
    “the use and sometimes misuse of antimicrobials in both human and veterinary medicine has resulted in the emergence of strains of bacteria that no longer respond to antimicrobial therapy.”

  • Doc Mudd

    The intrepid Bulger, erstwhile poet and relative novice to science (having accomplished in the biological sciences the equivalent of Webelo status and aspiring to rank of cub scout by ongoing master’s level studies at NYU) now deigns to sternly lecture us on points of microbial ecology.
    Bulger undertakes to do this, without benefit of formal training, simply because he holds an opinion…a layman’s opinion that, in his partisan mind is as lofty and meaningful as any, indeed, superior to most. Behold in Mike’s proud confusion a living, breathing example of an evangelist of “superficial observations of the world around us rather than deep analysis, shrill opinion rather than considered judgment”, a class of poseur anticipated by Andrew Keen in his book ‘The Cult of the Amateur’
    Bulger, in the true spirit of Keen’s modern amateur wallows noisily among “animations” and generic reports and assorted unscientific propaganda, crying out for relevant “sources” he is blissfully unaware of, and unable or otherwise too slothful to procure for his own edification. Well, here’s one relevant scientific source to get you started, Mikey:
    You might also find worthy background reading, Michael, in a book; ‘Quiet Killers: The Fall and Rise of Deadly Diseases’, authored by one Robert Baker, a specialist in infectious diseases and microbiology who lectures at Devon.
    Considering Keen’s apprehension, his warning of internet-emboldened self-styled lay “experts” and the potential damage they can achieve, it is dangerous to offer snippets of scientific information to someone like Mike. He will only misuse them. Informing a Keen “amateur” is the equivalent of handing a chimpanzee a loaded handgun – appalling to watch, even from a safe distance.
    Ah, well. Kumbaya, campers!

  • Michael Bulger

    I’m going to try to be brief, as I have quite a bit of work. First off, let me just say how pleasantly surprised I was that you actually responded with a real-life reference that really pertained to the discussion. Perhaps, this is the turning over of a new leaf? Now if only we could abandon the crass personal attacks and vulgar dung tossing that seems to propel you..
    The study you cite (Effect of the growth promoter avilamycin on emergence and persistence of antimicrobial resistance in enteric bacteria in the pig [2004]) does in fact show that after a period of withdrawal the resistance of the pathogens dropped significantly. Let’s pause there.
    Now, this was encouraging, save for the fact that resistance remained above the original levels that existed before the hogs were fed antibiotics. Additionally, it is discouraging that the MIC levels were so high during treatment. Documentation of the risk of farm workers contracting pathogens from animals, through animal contact, soil, and water, exists.
    A report of the FAO/OIE/WHO entitled “Non-Human Antimicrobial Usage and Antibiotic Resistance” also concurs that this “contributes to resistance problems in humans.” The WHO concluded that Sweden’s ban on antibiotics as growth promoters reduced the prevalence of resistant bacteria in animals. The National Research Council published that a “link can be demonstrated between the use of antibiotics in food animals, the development of resistant microorganisms in those animals, and the zoonotic spread of pathogens to humans.”
    So while it is interesting that post-treatment levels of antibiotic-resistance drops significantly in comparison to levels during the low-dosing of hogs, it is important to note that these levels are still elevated. Also, the variety of resistance genes present in treated hogs increased (as shown by your reference). Perhaps most important to remember is that hogs in treatment with significantly elevated levels of resistance can also transmit resistant pathogens to humans.
    The report, which I commend you so sincerely for sharing with all of us, is evidence of the importance of a adequate withdrawal period for treated hogs. Unfortunately, it is not evidence that antibiotic-feed results in lower levels of resistance (either during or after treatment). Quite the opposite.
    Sincerely, thank you for bringing the study to my attention. I will add it to my files. And, if I could take a moment to defend myself from your personal attacks, I would like to remind anyone concerned that these are not positions which I myself developed. Far from junk-science or the like, the basic premise of “low-dose antibiotics leading to resistance leading to human infection with resistant strains” is that of highly-qualified scientific bodies such as the FDA, CDC, AMA, and WHO. So instead of insulting me, it would better serve any agenda you might have to lead with credible references.
    As I said, I have other things I must attend to. I appreciate the reference. As I see it, the fact remains that the low-dose antibiotic feed increases resistance and contributes to a more varied resistance profile of the bacteria. It is great that a withdrawal period reduces the resistance levels. However, resistance still poses a threat and the subtherapeutic use of antimicrobials aggravates the situation.

  • Doc Mudd

    And a distracted egotistic young idealogue brashly dismisses accomplished scientists, sobering (and exciting) realities of ecology, microbiology, infectious disease…and a fascinating live experiment in India yielding important information to guide public health research.
    Trained in poetry, failed in science with definite prospects in politics. Just what we need, another vain politician determined to supplant venerated science-based institutions with silly mirages of woo and popular superstition.
    Oh well, amateurs – Andrew Keen is a prophet!

  • ICBM

    Et Tu Muddie? The only expertise YOU demonstrate in ANY of your posts is of the personal insult kind — that’s ALL you Got, Doc — and boy is it tiresome… But I guess if you don’t have a Life than bashing is what you do for a living………..
    …and in each of your posts — there it is, a Big Zero, plain as day for All to see, time after time. Sad really.