As the use of genetically modified crops becomes more practical, health concerns become increasingly relevant, both for humans as well as other organisms. While some research has focused on the effects of feeding genetically modified diets to organisms such as pigs and mice, little work has been done to observe the long term effects of feeding GM maize to dairy cows. Guertler et al. (2012) investigated the presence of nucleic acid or protein residue from GM maize in blood, milk, urine and feces, as well as testing for differences in apoptosis, inflammation, and cell cycle pathways between cows on GM and isogenic diets. The study finds no significant differences in any of these cell pathways, nor in the production or consumption of the cows. However, residue of the Cry protein produced in the GM maize was detected in feces.—Chad Redman
Guertler, P., Brandl, C., Meyer, H. H. D., Tichopad, A., 2012. Feeding Genetically Modified Maize (MON810) to Dairy Cows: Comparison of Gene Expression Pattern of Markers for Apoptosis, Inflammation and Cell Cycle. Consumer Protection and Food Safety 7, 195–202.
Guertler et al. noted the lack of long term analysis of the effects of GM crops being fed to livestock, leading them to perform a study on how a diet of GM maize can impact dairy cows in the long run. The process began simply, feeding 36 cows identical diets, with the exception that half were fed GM maize and the other half near perfectly isogenic maize. This stage of the procedure was conducted using crops that were grown in controlled conditions, as were animals, effectively controlling for all variables save the condition of eating GM maize.
During this 25 month period, the subject cows were monitored closely, having samples of feces, blood, milk, and urine taken throughout. The researchers were testing for the presence of Cry proteins and nucleic acids which are only present in GM maize. After the time period of 25 months, ten cows from the experimental group and seven from the control group were slaughtered, and tissue samples from the liver, rumen, abomasum, small intestine, large intestine, and appendix were removed and tested for the same Cry residue. The specific technique used to detect Cry residue was quantitative polymerase chain reaction (qPCR).
In order to access the cell pathways of apoptosis, inflammation, and cell cycle, Guertler et al. chose a reference and a target gene for each. The reference genes histone, ubiquitin and GAPDH were chosen because they were highly expressed in the sample tissues, giving researchers a base level to go by. The target genes, on the other hand, were chosen because their activation would indicate the activity of a cell pathway. Several specific target factors were analyzed for each of the three pathways in question using qPCR.
The results of this study are promising for the safety of GM crops. Guertler et al. did not discover any remnants of nucleic acids in any tested product of the experimental group of dairy cows. They did find traces of Cry protein in the feces of the cows, but this is not as concerning as it might have been had residue been discovered in milk or blood. The same holds for the sample tissues from the test group of cows; none of the organs showed a significant trace of the GM maize. These results basically show that, on a long run scale, GM maize and its products are not detectable in the cow that consumed it. What’s more, none of the target genes were expressed significantly differently from the reference genes. That means that, for these three major cell functions, there was no detectable impact from the GM maize diet. This clear paper does an outstanding job of presenting data that are promising for the future use of GM crops.