Cyclic exposure of poultry to drugs: Antimicrobial drugs discovered in feather meal used as food supplement

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  • Published: Apr 1, 2012
  • Author: Steve Down
  • Channels: Base Peak
thumbnail image: Cyclic exposure of poultry to drugs: Antimicrobial drugs discovered in feather meal used as food supplement

Feather fillers

Animal feed supplements made from poultry feathers contain antimicrobial drugs which will re-enter the food chain when fed to farm animals, say US researchers, in the first study of its kind. 

Poultry is the most common meat consumed in the US, with an annual production of 80 million turkeys and 9 billion broiler chickens, contributing to an average consumption rate of 45 kg per person, according to the USDA. That's a lot of poultry but the industry also produces a mountain of food waste, with about 33% of the total mass of animals being inedible.

Apart from the heads, bones and internal organs, about 2 billion kilograms of feathers are generated as waste but an industry has grown up around the feathers to recycle them into useful products. During rendering, the feathers are converted to a substance known as feather meal, which can be used to produce plastics and biofuels.

Two further applications of feather meal are as fertilisers and a component of animal feedstuffs, both of which are a potential cause for concern for human health. Recent studies by scientists in Chile have revealed that poultry feathers contain traces of antimicrobial drugs, given to the animals primarily to promote growth. So the feeds could reintroduce the drugs into the human food chain, supplementing the drug residues already present in the animals. Fertiliser use is a second possible route.

Building on the Chilean work, researchers from Johns Hopkins University, Baltimore, MD, and Arizona State University, Tempe, AZ, have investigated the levels of drugs in feather meal. David Love and coworkers decided to measure 59 pharmaceuticals and personal care products (PPCPs) to see if the drugs survived the rendering process which converts the feathers into meal.


Drugs recycled to poultry via meal supplements

The team purchased five samples of feather meals labelled as feed ingredients originating in the USA and China and seven samples of feather meal fertiliser from US sources. The PPCPs were extracted and analysed by liquid chromatography-tandem mass spectrometry with positive-ion electrospray ionisation, using an official EPA method for drugs in tissue which gave detection limits of 0.2-10 ng/g depending on the particular drug.

Every sample of feather meal contained antimicrobial drugs with 17 different drugs detected out of the 46 tested. They included sulphonamides (detection frequency 83%), macrolides (75%), fluoroquinolones (67%), tetracyclines (58%), folic acid antagonists (33%) and streptogramins (17%). Each sample contained at least two drugs, with the two Chinese samples the worst offenders concealing ten different drugs each.

One surprising find was the presence of fluoroquinolones in six of the ten US samples because these drugs have been banned in US poultry production since 2005. Their occurrence indicates that the ban is being flouted or that poultry feed is being contaminated by ingredients from industries that are not covered by the ban. Of course, once fluoroquinolones have entered the feed system, their migration into feathers used to produce meal establishes a cycle of re-exposure to the drugs.

Apart from the drugs, the team also tested for nine non-antimicrobial personal care products in the meals. Caffeine and its metabolite 1,7-dimethylxanthine were found in the majority of samples, possibly due to the use of coffee pulp and green tea powder in poultry feeds.

The pain reliever acetaminophen was detected in ten samples. It is used as a feed additive in China and is used legitimately in Europe to treat diseases in poultry. The other products included diphenhydramine (an antihistamine), thiabendazole (a fungicide and antiparasitic), fluoxetine (an antidepressant) and norgestimate (a sex hormone). There are a few literature reports describing the use of these PCPs in poultry and this was backed up by anecdotal evidence from poultry farmers collected by the team.

In practice, there may be more drugs present in the original feathers than were detected because thermally sensitive compounds will be degraded during the rendering process. The researchers illustrated this by heating feather meal dosed with the drugs in a simulation process. They did not use fresh feathers but the results went some way to explaining the absence of some drugs in meal and the presence of others.

"Further research would need to be performed to determine whether these drugs were present but denatured by the autoclaving process, or whether they were not present initially in unrendered feather meal, either through lack of exposure for the birds or lack of accumulation in the feathers," said Love and co-workers.

This is the first reported study of antimicrobial drugs and personal care products in poultry feathers and confirms a novel source of these drugs in animal feed. "Because this is the first study of PPCPs in feather meal, we invite independent verification of our results by others," the team declared.

However, they said that the consequences for human health remain to be resolved. "More work is needed to determine whether the detected levels of PPCPs in feather meal have an impact on the quality of food animal products and the safety of consumers."

Related Links

Environmental Science and Technology 2010 (Article in Press): "Feather meal: A previously unrecognized route for reentry into the food supply of multiple pharmaceuticals and personal care products (PPCPs)"

Article by Steve Down

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The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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