The longest duration of animal studies that we (DuPont Pioneer) conduct is 90 days, but it’s important to know that the feeding studies are just one part of the comprehensive testing we undertake for each new trait. The proteins that are expressed in these crops are tested extensively with laboratory studies and computer comparisons to make certain that they are not similar to proteins that are known to be allergenic or otherwise toxic.
We also conduct an extensive amount of composition testing where a GM plant will be grown in the field along with non-GM plants. When the grain is harvested, it is subjected to analytical chemistry testing to determine the concentration of the individual components we know are there. The concentrations of the different components are then compared between the GM and the non-GM plants. There is usually some variability in the concentrations of some of the different components, but that is nearly always observed in crops bred with traditional methods too. Therefore, the historic concentrations from non-GM crops are available at an open access website for further comparison. These methods have been very effective in demonstrating that GM technology does not introduce composition variability and that the grains obtained from these plants are “substantially equivalent” to those obtained from non-GM crops.
The 90-day rat feeding studies you are asking about have been conducted to assess the possibility that unintended changes could have occurred during the development process that may not have been detected in the chemical analysis. Ninety-day feeding studies in rats are common practice in supporting pre-commercialization product safety across many industries, including human pharmaceuticals, chemicals, etc. To date, no adverse effects associated with consuming diets containing GM grainhave been observed in any of these studies so there simply is no indication that longer term studies would be necessary.