Persistence of plant DNA sequences in the blood of dairy cows fed with genetically modified (Bt176) and conventional corn silage.

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.