Genetically modified (GM) crops, produced by introducing new genes into major crops using recombinant DNA technology, have raised several consumer concerns in the EU and elsewhere. As few GM crops are actually grown in the EU, the main consumer issues relating to freedom of choice have moved towards labelling of GM-derived foods and animals fed with imported GM feed.

Mandatory labelling of GM-plant-derived products has been introduced in several countries including Japan and the EU. This has resulted in many food companies discarding ingredients derived from GM plants or organisms. However, there has been little focus on the labelling of products from animals fed with GM plants or feed containing GM plants. Together with calls for traceability, consumers have also raised issues about the effects of DNA sequences from GM plants used as feed on animal health and products, and thus on human health.

The increasing use of GM organisms (GMO) worldwide has resulted in several studies examining the fate of dietary DNA and proteins from GMO in animals. Findings from these studies have suggested that GM-derived sequences could be detected in animals fed GM material. However, end-point PCR methods were generally used without identifying the amplicon which is required by international standards. In addition, there is a need for analytical control methods for detecting analytes (DNA or protein) derived from GM plants in animals or animal products.

A study by Bertheau et al.¹, investigated the presence of plant DNA sequences (including transgenic sequences) in animal blood, which is a complex intermediate between the digestive tract and animal matrices. Blood samples from Holstein cows fed with either Bt176 GM corn or conventional corn were examined using real-time PCR and sandwich ELISA analyses.

Results were unable to clearly show the presence of transgenic DNA or proteins in bovine blood, despite demonstrating the ability of small plant DNA fragments to cross the intestinal barrier. Findings indicated difficulties associated with detecting transgenic sequences in the blood of cows fed GM corn, and the lack of a cost-effective analytical procedure at present.
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¹ Bertheau, Y; Helbling, JC; Fortabat, MN; Makhzami, S; Sotinel, I; Audeon, C; Nignol, AC; Kobilinsky, A; Petit, L; Fach, P; Brunschqig, P; Duhem, K; Martin, P (2009). Persistence of plant DNA sequences in the blood of dairy cows fed with genetically modified (Bt176) and conventional corn silage. Journal of Agricultural and Food Chemistry 57 (2) 509-516.

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