Persistence of Plant DNA Sequences in the Blood of Dairy Cows Fed with Genetically Modified (Bt176) and Conventional Corn Silage

Abstract

To determine whether plant sequences, including transgenic sequences, are present in animal blood, we tested blood samples from Holstein cows fed with either Bt176 genetically modified corn or conventional corn. We used previously described sensitive real-time PCR assays targeting transgenic sequences (35S promoter and Bt176 specific junction sequence), a monocopy maize-specific sequence (ADH promoter), and two multicopy sequences from plant nucleus (26S rRNA gene) and chloroplast (psaB gene). The presence of Cry1A(b) protein in bovine blood samples was also tested using a sandwich ELISA kit. Our study shows the ability of plant nuclear and/or chloroplast DNA fragments to enter bovine blood circulation. However, maize nuclear DNA, both mono- and multicopy sequences, was less detected than chloroplast DNA, probably because the higher number of chloroplast copies and also possibly because nuclear DNA might be less protected by the nuclear membrane. Despite our data confirm the ability of small (ca.150 bp) plant DNA fragments to cross the intestinal barrier, we were unable to demonstrate clearly the presence of transgenic DNA or proteins in bovine blood. No sample tested positive with the two real-time PCR assays targeting transgenic sequences (35S promoter and Bt176 specific junction sequence). Only faint punctual positive results occurred randomly and were probably due to postsample collection or laboratory contamination or can be considered as artifact as they have never been confirmed. Our data highlight the difficulties to detect transgenic sequences in blood of dairy cows fed genetically modified corn (Bt176) silage. Those results show that in order to meet the consumers' demand of animals fed with GM products there is currently no cost-effective analytical procedure to replace documentary traceability.

Long-term feeding of genetically modified corn (MON810) — Fate of cry1Ab DNA and recombinant protein during the metabolism of the dairy cow

“…On the other side, a rapid degradation throughout the gastrointestinal tract takes place (Phipps et al, 2003;Wiedemann et al, 2006), which might explain the absence of recombinant DNA in blood after feed intake. The low number of copies of cry1Ab which might cross the intestinal barrier into the blood stream would also impede the tracing of a possible transfer of recombinant DNA into the blood stream (Bertheau et al, 2009). In contrary to Bertheau et al, end-point PCR was used in this study to detect plant DNA, which might explain the absence of small fragments of rubisco in blood samples.…”

“…In feces, blood and urine, a 206 bp fragment of cry1Ab could not be detected by means of PCR, which is in accordance to other studies (Einspanier et al, 2001;Phipps et al, 2003;Nemeth et al, 2004). On the one side, it is reported, that genomic DNA fragments are able to cross the intestinal barrier into the blood stream (Alexander et al, 2007;Bertheau et al, 2009). On the other side, a rapid degradation throughout the gastrointestinal tract takes place (Phipps et al, 2003;Wiedemann et al, 2006), which might explain the absence of recombinant DNA in blood after feed intake.…”

“…However, small fragments of recombinant DNA were also detected in milk samples from the Italian market, which the authors suspected to be due to feed and fecal contamination during milking (Agodi et al, 2006). Despite the finding, that DNA fragments can cross the intestinal barrier, neither fragments of cry1Ab DNA nor the Cry1Ab protein were detectable in blood (Bertheau et al, 2009). However, fragments of foreign DNA were found in blood and several organs of piglets (Mazza et al, 2005), in contents of all segments of the intestine of mice 2 h after feeding soybean leaves (Hohlweg and Doerfler, 2001), and in feces, blood and several organs of mice (Schubbert et al, 1997).…”

Assessment of Genetically Modified Organisms (GMO) in Meat Products by PCR

“…Model studies to detect GMOs in animal products have been carried out, showing that analysis of milk, muscle, or blood cannot serve as an indicator of the use of GMOs for feeding animals (Poms et al 2003 ;Nemeth et al 2004 ;Bertheau et al 2009 ), and a few However, particle size, composition, or heat and pressure processing might induce distortions in the results of GMO quantifi cation due to their infl uence on DNA degradation (Moreano et al 2005 ;Hird et al 2006 ). Then, cell membrane lysis by enzymatic activity and/or mechanical disruption is performed, mostly in the presence of detergents (guanidinium isothiocyanate, SDS, CTAB) and chelating agents (EDTA); cleanup steps come next, using organic solvents (chloroform, phenol); and fi nally, DNA is separated and concentrated by alcohol/salt precipitation (ethanol or isopropanol), affi nity, or ion/ exchange purifi cation columns (Hernandez et al 2005 ).…”

Considerations for Managing Agricultural Co-Existence between Transgenic and Non-Transgenic Cultivars of Outcrossing Perennial Forage Plants in Dairy Pastures

“…Although DNA fragments from high copy number endogenous plant genes such as rubsico have been detected in the blood and digesta [11,12], transgenic DNA (tDNA) has been shown to be broken down in the rumen and duodenum of cattle [9], and a number of studies have shown that tDNA was not detected in the milk of cows fed diets containing GM feeds [11,[13][14][15][16][17][18][19]. These data from milking trials are consistent with those from wide ranging reviews of animal production trials that have focused on meat producing animals [2,20] with the conclusion that there are no detectable or reliably quantifiable traces of GM feed components in eggs, meat, or milk [2,20].…”