Agriculture Reference
In-Depth Information
further harmonization to provide more
reproducible and scientii cally reliable data
sets that are not confusing to the public
(Snell et al ., 2012).
In summary, the exact biological
importance of the naturally occurring DNA
transfer into the animal remains
questionable. Due to highly fragmented feed
DNA and proteins present after digestion
within the GIT, the signii cant ef ects of GM
polymers on animals have never been
published. Generally, it can be stated that
recDNA fragments may survive the digestion
process and might only be detected in the
excretion of animals.
GM plants, it could be stated that similar
antibiotic-resistant genes were frequently
found in microorganisms of the conventional
environment, as well as within the untreated
animal. When investigating the specii c
ef ects of GM plant material on intestinal
microbiota, no signii cant inl uence on the
pattern of the microbial populations
persisting in bovine rumen was found under
Bt maize feeding (Einspanier et al ., 2004).
Similar experiments investigating horizontal
gene transfer in goats generated comparable
results (Rizzi et al ., 2008); a study performed
in pigs showed that the overall composition
of the caecal microbe population was almost
unchanged after GM feeding (Buzoianu et
al ., 2012). Such results indicate that Bt
maize feeding does not show obvious
inl uences on the intestinal microbiota of
dif erent farm animals.
As shown by dif erent authors (Clark et
al ., 2005; Gruber et al ., 2011), excreted Cry-
protein fragments persist during slurry
storage but are degraded successively after
spreading on the i elds. Deduced from these
reports, the delivery of excreted, partially
digested Bt proteins into the normal
agricultural environment will result in their
total degradation within months.
Another interesting point deals with
game animals, such as wild boar and deer,
being considered as uncontrollable targets
and distributors of GM plant material in the
environment (Guertler et al ., 2008).
Currently, there is no scientii c indication
for dif erent behaviours of these animals
concerning ingestion, digestion and
excretion of fed recDNA or recProteins when
compared with the formerly observed fates
of recDNA and recProteins in farm animals.
An upcoming concern will be the
introduction of newly developed GM crops
of the next generation. In the case of
transplastomic GM crops, the chance to
detect thereof derived more enriched
recDNA, for example in animal products like
meat, milk or eggs, may arise.
One more item may concern potential
synergistic and cross-ef ects between GM
forage plants and animals under specii c
stress (stacked traits, diseased, weaned and
9.3 Special Issues Concerning
Distribution of Transgenic Polymers
From the above-mentioned studies, it is well
known that fragmented Cry-DNA and
degraded Cry-proteins are detectable within
the content of the animal's GIT and therefore
may subsequently be excreted. h is fact
might indicate potential interactions of
recDNA/recProteins with the environment,
concerning, for example, horizontal gene
exchange with the microbiota or the ef ects
of Cry-peptides on the pattern of soil
organisms. Currently, the hypothetical
horizontal gene transfer of feed recDNA to
intestinal bacteria or the mammalian
genome must be considered very unlikely.
h is statement is supported by the
observation that neither the presence of
plant genes nor an expression of foreign
genes has ever been observed in animals
(Einspanier and Flachowsky, 2009;
Flachowsky and Wenk, 2010). In addition,
the potential horizontal gene l ow among
microorganisms was formerly discussed as a
possible mechanism for spreading novel
genetic material into the environment
(Nielsen and Townsend, 2004). However,
the horizontal transfer of novel genes from
GM plants to microorganisms may be
neglected under i eld conditions (Brigulla
and Wackernagel, 2010). When searching
for antibiotic-resistant genes, which were
initially present in some i rst-generation
 
 
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