Agriculture Reference
In-Depth Information
threefold between 2001 and 2012, probably
due to increased agronomic productivity
and decreased use of pesticides. Beside the
more than 28 commercialized transgenic
traits, herbicide-tolerant (EPSPS) and/or
insect-resistant (Cry-toxin) maize and
soybeans are currently the dominant GM
crops. Interestingly, developing countries
are at present in the majority and have
shown obviously higher increase rates
within the last years in planting GM crop
compared with the industrial countries
(ISAAA, 2011). For example, in 2012 more
than 70% of the world production of
soybeans contained GM varieties routinely
used as the major protein source in farm
animal feed. Furthermore, it is expected
that a new generation of transgenic plants
will be commercialized and will further
increase the spectrum and global abundance
of GM forage plants in the future (see
Chapter 12). As a practical consequence, the
continuous increase of GM crop production
makes these crops an important source for
farm animal feeding. For example, in
Germany more than 90% of feedstuf for
pigs contains GM material (Bendiek and
Grohmann, 2006), indicating that, based on
European regulations, feed containing
>0.9% GM components must be labelled.
h e ubiquitous monitoring approach is to
trace distinct recDNA sequences within feed
or animal substrates (dif erent organs and
secondary products like meat, milk and
eggs) after GM plant feeding. As has been
reviewed before (Phipps et al ., 2006;
Alexander et al ., 2007; Einspanier and
Flachowsky, 2009), a broad scientii c
knowledge regarding the uptake, ef ect and
disposition of GM feed in animals is
nowadays available. Despite the fact that
nearly all studies were unable to discover a
specii c health problem for animals fed
commercialized GM plants (see Chapters
6-8), some concerns about the fate and
impact of consumed transgenic biopolymers
(recDNA, recProteins) and derived food
products thereof are still being publicly
debated (Fagerstroem et al ., 2012).
In general, DNA and proteins are common
components of feed, and after ingestion, a
rapid intestinal degradation into short
fragments has been suggested. Based on the
fact that a complete destruction of feed DNA
and proteins during digestion will not occur,
adopted international safety assessments
have been liberated (EFSA, 2008, 2011).
h is chapter summarizes the animal feeding
studies published to date concerning the
fate of GM feed DNA and proteins, together
with the resulting signii cance and con-
sequence of a potential GM transfer into
animals and their secondary products, and
the correlating safety aspects.
9.2.1 The fate of ingested feed DNA
Initially, it has to be acknowledged that the
integrity of dietary DNA remains stable
enough during feed processing to become
the most suitable molecule for forensic
approaches. One of the i rst studies
introducing the tracing of feed DNA within
farm animals fed GM crops provides
essential results about the presence and
distribution of ingested DNA in selected
tissues (Einspanier et al ., 2001). By use of
specii cally developed, highly sensitive
amplii cation techniques (polymerase chain
reaction, PCR), it is nowadays possible to
trace single DNA molecules quantitatively in
most complex samples (Einspanier, 2006).
However, due to the variety of dif erent
methods, severe specii city problems arise
(sample preparation, normalization, cross-
contamination), directly interacting with
the reliability of the generated results.
h erefore, confounded data interpretations
are unavoidable when inadvertent DNA
contaminations distort such extremely
sensitive PCR assays; for example, when
detecting highly abundant plant genes
versus single copy genes (Klaften et al .,
2004). In this context, it has to be asserted
that nearly all feeding studies use sensitive
PCR techniques searching for foreign DNA
in animal tissues or secondary products.
Only in conjunction with optimized and
professional sample selection and process-
ing, contamination-free DNA extraction,
and suitable (real-time) PCR methods will
reliable data interpretation be possible.
h erefore, all studies should cope carefully
 
 
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