At the request of the SPD, the Bavarian Parliament decided in May 2005 to undertake a long-term feed trial with genetically modified Bt maize.
Two groups of 18 milk cows each were fed the maximum portion of maize according to their needs over a period of 25 months. One group was fed genetically modified Bt maize MON810, the other with a conventional maize (isogenic) variety that was identical except without the active ingredient, a Bt protein. The milk cows fed MON810 maize ingested 5.3 mg of Bt protein daily.
Both the Bt and conventional maize were grown under similar conditions in Bavaria. During the trial, each group lost nine cows as a result of illness or infertility. These were replaced by young cows.
Blood, milk and excrement samples from each cow were tested monthly. The feed was examined weekly. A total of 19,000 samples were analysed in each of the two groups. The Bavarian feed trials on the influence of Bt maize on cow milk cover a significantly longer trial period and a greater number of animals than any other similar trial carried out to date.
Milk production was the same in both groups. After being fed Bt maize for 25 months, no indication was found that this has any influence on animal health or fertility. Nutritional content and calorific values were the same for both the Bt and the conventional maize feed.
The DNA analysis techniques used in this study were further developed. Despite improved detection sensitivity and higher sampling intensity, no indication was found of a transfer of transgenic components from the Bt maize to the milk. "There was no difference at any time between the milk of cows fed isogenic maize or transgenic maize," said Assistant Secretary Friedrich Mayer during the presentation of the study in the agricultural committee of the state parliament.
The trials were carried out at the Munich Technical University (Weihenstephan Science Centre) and at several agricultural research facilities in Bavaria.