Agriculture Reference
In-Depth Information
with a minimum of harmonization and
standardization of used DNA-based
detection methods avoiding irrelevant data
sets.
Since the earliest studies investigating
DNA degradation in farm animals fed
conventional versus GM plants, it is now
generally accepted that nucleic acids are not
completely degraded during digestion.
Fragments of highly abundant plant DNA
(e.g. chloroplast genomes) are routinely
found in the digestive tract and/or specii c
organs of distinct farm animals (cattle,
chicken); Fig. 9.1 depicts a theoretical
deduced route of feed DNA in animals. In
contrast, no transgenic or conventional
plant DNA fragments have been found in pig
or i sh organs (Sanden
et al
., 2004; Walsh
et
al
., 2011). One exception is bee honey, where
native pollen particles collected from GM
plants are, in principle, present, causing
positive GM signals. For example, the
presence of recDNA pollen in honey initiates
massive public concerns and subsequently
might provoke specii c legal decisions. But
recent studies have documented that even
the adverse ef ects on the vitality of
honeybees directly fed Bt pollen can be
neglected (Duan
et al
., 2008; Hendriksma
et
al
., 2011).
In conclusion, small fragments of feed
DNA will pass through the intestinal tract
and appear in some body tissues of some
farm animal species. No transfer of recDNA
from commercialized GM crops has been
reliably detected in animal organs or
secondary animal products like meat, milk
or eggs, as supported by the majority of
publications investigating the fate of
ingested feed DNA in animals (Alexander
et
al
., 2007; Einspanier and Flachowsky, 2009).
No data have ever indicated that transgenic
DNA and native plant DNA are degraded
dif erently during feed processing and
digestion in animals.
Due to the fact that dietary proteins are
mostly denatured during feed preparation
and the subsequent digestion process, a
reliable measurement of degraded feed
proteins is challenging. h erefore, the
minority of published studies deal with the
detection of GM proteins, because trace
amounts and fragmented proteins are hardly
detectable due to missing the exponential
amplii cation technology of DNA. However,
by using highly sophisticated immunoassays,
it is nowadays possible to trace degraded
recProteins satisfactorily during GM feed
processing and intestinal digestion. When
summarizing all the current publications, it
was found that a rapid degradation of Cry-
toxin from Bt maize had been measured
within the bovine gastrointestinal tract
(GIT) (Lutz
et al
., 2005; Wiedemann
et al
.,
2006; Paul
et al
., 2010), the pig
gastrointestinal tract (GIT) (Walsh
et al
.,
2012) and in the chicken (Scheideler
et al
.,
2008). All published data ai rm a rapid
degradation and fragmentation of Bt pro-
teins, starting with ensiling and continuing
during the digestion process in all animals
investigated. A specii c allergic potential of
GM-feed
uptake
Intestinal
tract
Lymph/immune
/blood system
Meat
Animal
tissues
Milk
recProtein
recDNA
Eggs
Fragmented recProtein
Fragmented recDNA
Fig. 9.1.
Potential transfer of recombinant feed components in animals.
