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[SANET-MG] transgenic DNA from feed in tissues of sheep and pigs
J. Agric. Food Chem., ASAP Article 10.1021/jf052459o S0021-8561(05)02459-3
Web Release Date: February 10, 2006
Detection of Transgenic and Endogenous Plant DNA in Digesta and Tissues
of Sheep and Pigs Fed Roundup Ready Canola Meal
Ranjana Sharma, Dana Damgaard, Trevor W. Alexander, Mike E. R. Dugan,
Jennifer L. Aalhus, Kim Stanford, and Tim A. McAllister*
Agriculture and Agri-Food Canada Research Centres, Lethbridge, Alberta,
Canada T1J 4B1, and Lacombe, Alberta, Canada T4L 1W1, and Alberta
Agriculture, Food and Rural Development, Lethbridge, Alberta, Canada T1J
4V6
Abstract:
The persistence of plant-derived recombinant DNA in sheep and pigs fed
genetically modified (Roundup Ready) canola was assessed by PCR and
Southern hybridization analysis of DNA extracted from digesta,
gastrointestinal (GI) tract tissues, and visceral organs. Sheep (n = 11)
and pigs (n = 36) were fed to slaughter on diets containing 6.5 or 15%
Roundup Ready canola. Native plant DNA (high- and low-copy-number gene
fragments) and the cp4 epsps transgene that encodes 5-enolpyruvyl
shikimate-3-phosphate synthase were tracked in ruminal, abomasal, and
large intestinal digesta and in tissue from the esophagus, rumen,
abomasum, small and large intestine, liver, and kidney of sheep and in
cecal content and tissue from the duodenum, cecum, liver, spleen, and
kidney of pigs. High-copy chloroplast-specific DNA (a 520-bp fragment)
was detected in all digesta samples, the majority (89-100%) of
intestinal tissues, and at least one of each visceral organ sample
(frequencies of 3-27%) from sheep and swine. Low-copy rubisco fragments
(186- and 540-bp sequences from the small subunit) were present at
slightly lower, variable frequencies in digesta (18-82%) and intestinal
tissues (9-27% of ovine and 17-25% of porcine samples) and infrequently
in visceral organs (1 of 88 ovine samples; 3 of 216 porcine samples).
Each of the five cp4 epsps transgene fragments (179-527 bp) surveyed was
present in at least 27% of ovine large intestinal content samples
(maximum = 64%) and at least 33% of porcine cecal content samples
(maximum = 75%). In sheep, transgene fragments were more common in
intestinal digesta than in ruminal or abomasal content. Transgene
fragments were detected in 0 (esophagus) to 3 (large intestine) GI tract
tissues from the 11 sheep and in 0-10 of the duodenal and cecal tissues
collected from 36 pigs. The feed-ingested recombinant DNA was not
detected in visceral tissues (liver, kidney) of lambs or in the spleen
from pigs. Of note, however, one liver and one kidney sample from the
pigs (different animals) were positive for a 278-bp fragment of the
transgenic cp4 epsps (denoted F3). Examination of genomic libraries from
these tissues yielded no conclusive information regarding integration of
the fragment into porcine DNA. This study confirms that feed-ingested
DNA fragments (endogenous and transgenic) do survive to the terminal GI
tract and that uptake into gut epithelial tissues does occur. A very low
frequency of transmittance to visceral tissue was confirmed in pigs, but
not in sheep. It is recognized that the low copy number of transgenes in
GM feeds is a challenge to their detection in tissues, but there was no
evidence to suggest that recombinant DNA would be processed in the gut
in any manner different from endogenous feed-ingested genetic material.
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