The ecology of antibiotic resistance on farms is complicated. Animals receive antibiotic doses in their food and water, for reasons of growth promotion, disease prophylaxis, and treatment. Other chemicals in the environment, such as cleaning products or antimicrobial metals in the feed, may also act as drivers of antibiotic resistance. Antibiotic-resistant organisms may also be present in the environment already, from the air, soil, or manure pits within or near the barns. Ecologically, it's a mess and makes it more difficult to attribute the evolution and spread of resistance to one particular variable.
A new paper emphasizes just what a mess it really is, and what animals are exposed to in addition to "just" antibiotics. Led by Keeve Nachman at the Johns Hopkins University Center for a Livable Future, his team took a different approach to examining farm exposures, by looking at "feather meal." What is feather meal, you may ask? I did when I met with Keeve last month at Hopkins as we discussed his research. Well, feathers are one obvious byproduct of chicken slaughtering, and waste not, want not, right? So feathers are processed into meal, which can then be used in a number of ways--among them fertilizer, and as an additive to feed for chickens, pigs, fish, and cattle.
We already knew that chickens receive antibiotics in their food and water supplies, just as other farm animals do. It was also known that some antibiotic residues persisted on chicken feathers--another potential driver of resistance in farm animals. However, Nachman and colleagues wanted to assess what other chemicals may be present in this feed meal besides antibiotics, and also whether those antibiotic residues persisted in the feather meal after processing/treatment of the feathers. As lead author David Love notes:
Why study feather meal? We know that antibiotics are fed to poultry to stimulate growth and to make up for crowded living conditions in poultry houses, but the public does not know what types of drugs are used and in what amounts. It turns out that many of these drugs accumulate in poultry feathers, so by testing feathers we have a non-invasive way of learning about what drugs are actually fed to poultry.
To do this, they examined 12 feather meal samples from the U.S. (n=10) and China (n=2). All 12 samples contained at least one antibiotic residue, and some contained residues of 10 different drugs (both of those were from China). While many of the antibiotics were ones used in poultry farming (or their metabolites), they also found drugs they did not expect. Most significantly, this included residues of fluoroquinolones, which they found in 6 of 10 U.S. feather meal samples. Why is this important? Fluoroquinolone use was banned in U.S. poultry production as of 2005 because of the risk to human health--so where are these residues coming from? The authors make a few suggestions for this:
These findings may suggest that the ban is not being adequately enforced or that other pathways, for example, through use of commodity feed products from livestock industries not covered by the ban, may inadvertently contaminate poultry feed with fluoroquinolones. Furthermore, if feather meal with fluoroquinolone residues is fed back to poultry, this practice could create a cycle of re-exposure to the banned drugs. Unintended antimicrobial contamination of poultry feed may help explain why rates of fluoroquinolone-resistant Campylobacter isolates continue to persist in poultry and commercial poultry meat products half a decade after the ban.
Interestingly, the authors tested whether antibiotic residues at the level they found could influence bacterial growth, and found that they did inhibit growth of wild-type E. coli, but allowed a resistant strain to flourish.
Besides antibiotic residues, a number of other chemicals were also detected, including many I'd never thought to associate with farming. In the U.S. samples, they found caffeine--apparently chickens may be fed coffee pulp and green tea powder, which may account for this finding; acetaminophen (Tylenol), which can be used to treat fevers in poultry just as it can for humans; diphenhydramine (the active ingredient in Benadryl), which apparently is used for anxiety issues in poultry; and norgestimate, a sex hormone. Any kind of health significance to these (either to people or to the animals who are ingesting these via feather meal) is uncertain. In an interview with Nick Kristof in the New York Times, Nachman noted:
"We haven't found anything that is an immediate health concern," Nachman added. "But it makes me question how comfortable we are feeding a number of these things to animals that we're eating. It bewilders me."
So what we're seeing here are the presence of antibiotics and other drugs in feather meal, which is spread around as a fertilizer or fed to many species of domestic animals as an additive. It's difficult to keep up with these additional feed additives--in addition to feather meal, many animals could also receive distiller's grains in their diet, ethanol by-products which are another potential source of antibiotic residues.
This, my friends, is a clusterfuck.
Though I've focused on the U.S. data here, the paper notes that the Chinese samples are relevant as well--while most feather meal used here is domestically produced, we do import some, and about a quarter of what we import is from China, where antibiotics that are restricted or banned in the U.S. may still be in use. Furthermore, farmers may not even know this is in the feed they're using, as many mixes are proprietary. (And if farmers don't know, you can imagine how difficult it is for a researcher to determine if this is playing a role in antibiotic resistance or other public health issues on these farms).
Works cited
Love, D., Halden, R., Davis, M., & Nachman, K. (2012). Feather Meal: A Previously Unrecognized Route for Reentry into the Food Supply of Multiple Pharmaceuticals and Personal Care Products (PPCPs) Environmental Science & Technology, 46 (7), 3795-3802 DOI: 10.1021/es203970e
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Flourouquinolone??? As someone who has had to take Cipro a number of times for complicated UTIs, that disturbs me. Plus, it should absolutely be out of the feed chain for cattle, since cattle are vectors for anthrax, and that's one of the main *treatments* for anthrax.
Yikes!
I'm glad they did this study. I wonder what the solution will be. I mean, we can't withhold all medications from food animals; that would be inhumane. They deserve to have their problems treated. But certainly we could discontinue routine dosing with prophylactic antibiotics and hormones. And there have to be other solutions to the anxiety issues. You don't want your chickens pecking each other to death, and it would be good to have an alternative to battery hen situations that isn't pharmaceutical.
To follow on CA's sound comments, I add this about the last line: THe answer to the battery cage system is at the supermarket where eggs from open housed hens are labeled and sold alongside regular ones. I observe that for every cage-free egg carton, there will be ten cheaper, unmarked cartoon facings (rows).
Unforunately price means that much more to shoppers over humane conditions. The supermarket execs also look at this as a specialty: Stick it to the consumer (higher mark up).
I worked two months in a battery layer operation and have kept backyard flocks. Tho 90% of birds would produce in cages, but their feathering was very poor and it was so unnatural and a cruel system. Course they didnt get devoured by racoons, hawks, etc.
You cant feed 300 million people with eggs gathered from small flocks...not enough land or willing workers.
Still, check the supermarket facings for progress on the issue.
Excellent post, Dr. Smith. Clusterfuck sums it up quite nicely.
As a home brewer, I was also struck by the feeding of mash grains to animals. Since the purpose of mashing is to help convert starches to fermentable saccharides, I would be quite curious what nutrient value the discarded mash grains have for the animals. In addition to the horrific conditions in concentrated animal feeding operations, adding mash grains seems like yet another cruelty if these are little more than nutrient depleted fibrous filler.
Not a good article to read while eating chicken nuggets...
Jed Clampett II:
Yeah; I buy cage-free eggs whenever possible for this reason. But there is the problem that chickens are, honestly, little bastards at times. They can peck the dickens out of one another, and it's easy to get them stressed. One of the advantages of caging them is that they (theoretically) can't reach one another to do this. The solutions are all imperfect; maybe we need a Temple Grandin for poultry.
Dave, much of the spent grain is from alcohol for fuel. They use antibiotics to suppress lactic acid bacteria which ferment sugars to lactic acid instead of alcohol, usually penicillin and virginiamycin. . Only the alcohol is removed, so the proteins and minerals should remain. The spent grain tends to be high in phosphate. The use of those spent grains as feed is not regulated.
The effect of antibiotics on weight gain and feed efficiency was first discovered by using the spent fermentation residues from the generation of antibiotics as feed.
There are lots of cross-resistance pathways, so exposure to one antibiotic tends to increase resistance via broad resistance pathways to other antibiotics.
This makes me wonder if poultry farms here in the Philippines have problems like this.
daedalus2u:
Many thanks for the eye-opening information. I had no idea that antibiotics were used in ethanol production. That is very disconcerting.
Silly me, I quoted from the top search result, which was a 2005 claim of no antibiotic residues.
Further down in the search results:
What We Know about Feeding Dried Distillers Grains ...
antibiotic residues were detected in 24 of 45 samples. ⦠... FDA to detect antibiotic residues as low as 0.1 ppm (dry matter basis) ...
www.ddgs.umn.edu/.../2009-Shurson-%20George%20Young%20Conference.pdf
That is disturbing for so many reasons.
My local Safeway had 'organic garlic' from China and US garlic from California. I don't subscribe to conspriacy theories but what would you think is safer?
I try to buy local food, but, but, but unless you know your farmer you don't know what you get.
Ken
Yuck. I'm all about reducing waste and increased efficiency, but not when it makes things worse! Eww...
Many thanks for the eye-opening information. I had no idea that antibiotics were used in ethanol production. That is very disconcerting.
Ditto. I like to think of myself as knowledgeable about agriculture and science but I had never heard of this before. And not to go OT, but has not the entire ethanol mess turned out to be a total disaster? (Or a clusterfuck, to borrow Dr. Smith's scientific description.)
Most people have no idea what chickens, pigs, cows or fish are fed. When I tell them at work, they can hardly believe it. Several years ago, I engaged Kroger in a conversation about the need for food labeling. At first, I was given pat answers and a pat on the head so to speak, now go buy our stuff and leave us alone. lol Well, I didn't and upped the ante, at one point saying they were forcing us to be part of a food experiment, because knowledgeable consumers cannot make informed decisions. I told them if they looked at their customers the way a rancher looks at his cattle, it would be obvious they have a big problem. You would have to be blind not to see how cruel bad food is to many people. Some are so big and fat they can hardly waddle. Even young kids. The good news is, they have adopted their own line of organic food, called Simple Truth. I want to give credit where credit is due. Thank you Kroger.
I have recently been looking for an organic nitrogen fertilizer to add to my garden. Organic feather meal seems like a good alternative, right? Turns our that feather meal from any source is an approved input in any organic farming (not animal raising) operation. So even organic products may be further contaminated and soil microorganisms made resistant via the USDA approved use of animal byproducts, regardless of source, for growing "organic" plants. I buy only organic, but find the organic regs frequently fraudulent to the normal consumer. Write to the USDA to change the regs to make source of such inputs organic only for organic final products.