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DNA Barcoding Study Finds South African Game Meat Labels Often Unreliable

NEW YORK (GenomeWeb News) – A study that used DNA barcodes to identify source animals in commercially sold meat in South Africa found that the majority of game meat samples contained animals other than those described in product labeling.

As described online today in the journal Investigative Genetics, a team from South Africa and Argentina used sequences from two mitochondrial genes — cytochrome c oxidase subunit I and cytochrome b — to barcode almost 150 commercial meat samples from South Africa, focusing on beef and wild game products.

The beef samples all checked out, evidently containing only beef as listed. But results for game products were much more variable. There, the analysis revealed rampant inaccuracies in food labeling, with more than three-quarters of the game meat samples yielding sequences from animals not mentioned in product labels. In one instance, barcode sequences suggested that some of the substituted meat came from cape mountain zebra, a species listed as endangered by the Convention on International Trade in Endangered Species, or CITES.

"The reliability of commercial labeling of game meat in South Africa is very poor," corresponding author Maria Eugenia D'Amato, a researcher with the University of the Western Cape's forensic DNA lab, and her co-authors concluded.

They explained that "extensive substitution of wild game has important implications for conservation and commerce, and for the consumers making decisions on the basis of health, religious beliefs, or personal choices."

Meat from southern African game animals is finding favor in the area, especially among those looking for natural, lean forms of meat, the team explained.

Though most South African regulations call for wild meat products to be accompanied by a permit and processed at an accredited slaughterhouse, seasoned and dried strips of game meat called biltong — which can come from wildlife farms, families, or hunters — are not necessarily subjected to such inspection, according to D'Amato and colleagues.

"Biltong is manufactured both industrially and in small-scale family businesses, resulting in a mixed market of branded and unbranded products," they wrote. "The labeling of game meat and biltong relies largely — or solely — on wholesalers and manufacturers."

In an effort to understand how well meat labels matched up with products, the group turned to DNA barcoding for food identification — an analysis that also made it possible to gauge the utility and limitations of different DNA sequences and analytical approaches for such applications.

The study centered around 146 meat samples collected in South Africa. Of these, 14 were labeled as containing beef, while the ingredients for 132 samples listed wild game animals such as ostrich, kudu, wildebeest, and springbok.

The group barcoded each sample by amplifying stretches of mitochondrial DNA encoding parts of the cytochrome c oxidase subunit I and cytochrome b genes by PCR before sequencing these amplicons by Sanger sequencing.

Bits of the cytochrome b gene have been sequenced for studies going back more than two decades, leading to a fairly robust collection of these sequences, researchers noted, while a slew of more recent data on cytochrome c oxidase subunit I sequences have come out of projects including the Barcode of Life effort.

Both barcodes have been proposed for forensic or conservation science, they explained, with some suggesting that the cytochrome b gene provides better species resolution or phylogenetic information and others favoring cytochrome c oxidase subunit I sequences.

A 2009 study in Conservation Biology demonstrated that it was possible to discern between bushmeat samples from dozens of mammal and reptile species using part of cytochrome c oxidase subunit I as a barcode, for example.

Even so, authors of the new study explained that there are still far fewer cytochrome c oxidase subunit I than cytochrome b sequences in the GenBank database when considering ungulate animals often found in game meat in southern Africa.

Consequently, they opted to test both regions, using multiple analytical methods to identify each sample from these barcodes. In so doing, the researchers found a wide range of animal species — from beef to blesbok and blue wildebeest.

Unlike product tests that have made headlines in Europe of late, though, inaccurate labeling issues were not identified for beef samples. In fact, the group's barcoding analyses verified all 14 beef samples as authentic.

That was not always the case for the game meat. Based on DNA sequences detected, just over 76 percent of game samples appeared to contain meat from an animal not listed amongst the product ingredients.

In supposed ostrich samples, for instance, the team tracked down DNA sequences from springbok, kudu, black wildebeest, kangaroo, lamb, pork, and beef. Samples described as kudu or springbok sometimes contained beef, lamb, horse, kangaroo, or alternative game species such as hartebeest or eland.

Such slips don't just impact consumers, D'Amato and her colleagues explained. They may also be important from a wildlife conservation standpoint.

In the current study, investigators identified cape mountain zebra meat in a sample ostensibly made up of kudu — a potential concern since the zebra species is CITES-listed and classified as vulnerable by the International Union for Conservation of Nature.

On the flip side, the analysis made it possible for researchers to get a peek at the utility of using barcodes to identify various animal species from southern Africa.

Limitations in this process still exist, they explained, in part due to the incomplete nature of barcode-containing databases. Still, the reliability and applicability is expected to continue growing as researchers put together more complete catalogs of DNA barcodes that capture genetic variation across animal species or populations.

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