There have been some concerns that functional transgenes from GM-derived feed materials might be incorporated into livestock products for human consumption (milk, meat and eggs). Biologically active genes and proteins are common constituents of food and feed, but digestion in both animals and humans is known to rapidly degrade their DNA, and the subsequent uptake of DNA fragments from the intestinal tract into the body is a normal physiological process.
In a statement published on 20 July 2007, EFSA advised that 'a large number of experimental studies with livestock have shown that recombinant DNA fragments or proteins derived from GM plants have not been detected in tissues, fluids or edible products of farm animals such as broilers, cattle, pigs or quails'.
When reviewing the issue later the same year, EFSA noted that 'the recombinant sequence is present in the GM plant only as a single or low copy number, which makes the potential absorption a rare event and therefore difficult to detect', and that 'when more studies are carried out with more sensitive detection methods, such recombinant DNA fragments may be more frequently found in the future'. It is therefore possible that DNA fragments derived from GM plant materials may occasionally be detected in animal tissues, in the same way that DNA fragments derived from non-GM plant materials can be detected in these same tissues. EFSA also noted that 'no technique is currently available to enable a valid and reliable tracing of animal products (meat, milk, eggs) when the producer animals have been fed a diet incorporating GM plants'.