Investigations and Concerns about the Fate of Transgenic DNA and Protein in Livestock

Abstract

The fate of transgenic DNA (tDNA) and protein from feed derived from Genetically Modified organisms (GMOs) in animals has been a major issue since their commercialization in 1996. Several studies have investigated the risks of horizontal gene transfer (HGT) of tDNA and protein to bacteria or animal cells/tissues, but some of the reported data are controversial. Previous reports showed that tDNA fragments or proteins derived from GM plants could not be detected in tissues, fluids, or edible products from livestock. Other researchers have shown that there is a possibility of small fragments entering animal tissues, fluids and organs. This motivated us to update our knowledge about these concerns. Therefore, this review aimed to evaluate the probable transfer and accumulation of tDNA/proteins from transgenic feeds in animal samples (ruminant and non-ruminant) by evaluating the available experimental studies published scientifically. This study found that the tDNA/protein is not completely degraded during feed processing and digestion in Gastro-Intestinal Tract (GIT). In large ruminants (cattle), tDNA fragments/proteins were detected in GIT digesta, rumen fluid, and faeces. In small ruminants (goats), traces of tDNA/proteins were detected in GIT digesta, blood, milk, liver, kidney, heart and muscle. In pigs, they were detected in blood, spleen, liver, kidney, and GIT digesta. In poultry, traces were detected in blood, liver and GIT digesta but not in meat and eggs. Notwithstanding some studies that have shown transfer of tDNA/protein fragments in animal samples, we cannot rely on these few studies to give general evidence for transfer into tissues/fluids and organs of farm animals. However, this study clearly shows that transfer is possible. Therefore, intensive and authentic research should be conducted on GM plants before they are approved for commercial use, investigating issues such as the fate of tDNA or proteins and the effects of feeding GM feed to livestock.