Jun 2, 2006

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Feedstuff from GM and conventional crops

No difference in quality

For the health and performance of farm animals it makes no difference whether their feed contains components from genetically modified plants or only conventional plant material. This is the conclusion reached by researchers of the research centres within the German Ministry of Agriculture. In an article in the ForschungsReport journal they summarise the findings of their own experiments as well as the available scientific literature on the topic.

The federal research centres investigated the contents of the GM feed and also carried out feeding experiments on various farm animals, in some cases over several generations.

Feeding experiments with genetically modified plants are designed to achieve two main research aims:

• Firstly, they are part of the safety assessment of genetically modified plants and enable conclusions to be drawn about human health.
• Secondly, these kinds of experiment can be used to compare the nutritional value of animal feed from genetically modified and conventional plants. This is important, because the majority of the GM crops grown worldwide are fed to farm animals. Researchers at the Federal Agricultural Research Centre in Braunschweig (FAL) have conducted 17 of these feeding experiments over the past few years. Worldwide, the findings from 100 feeding experiments with GM plants have been published.

Ten quail generations: feeding with genetically modified maize

The trial animals studied in Germany included ruminants like dairy and beef cattle, as well as pigs and poultry.

For each animal species the FAL researchers compared two trial groups. The feed given to one group had a GMO content of 20 to 80 percent, while the other group was fed comparable conventional feed.

After a certain trail period factors relevant for the animals’ performance and health were measured, such as the weight of the young animals. Depending on the species, the feeding experiments lasted up to 250 days (pigs and cattle). A long-term trial was conducted for quails which measured their weight, laying rate and hatching rate over ten generations.

The researchers were unable to identify any significant differences between the animals fed on GM feed and those fed on conventional feed in any of the 17 series of feeding experiments. The content analyses corroborate this essential equivalence, because here too, the researchers found no difference: apart from the genetically inserted proteins and DNA segments, the substances contained in the genetically modified and conventional parent plants were the same – within the range of normal natural variation.

The internationally published study findings also tie in with those of the German research centres. Only one difference was found between feedstuffs from genetically modified and conventional plants in various studies: animal feed from Bt maize often contains lower quantities of harmful fungal toxins (mycotoxins) than conventional maize feed. This is because the insect-resistant Bt maize plants are attacked less frequently by mould fungi.

The GM plants currently used commercially generally have modified cultivation properties. The fact that the nutritional value and substances contained in these plants are no different from those of conventional plants is therefore in line with the original expectations and objectives of the plant breeders. In future, the main focus will be on modifying the content and nutritional characteristics of plants using genetic methods. With these types of crop, so the Ministry of Agriculture researchers believe, it will be particularly important to investigate whether the new substances in the plants have nutritional physiological effects and what these are.

New DNA, new proteins: break-down in the body

In their article, the researchers from the federal research centres also summarise the findings regarding the breakdown of the new substances contained in the GM plants. These include new DNA segments and the new proteins formed as a result of the inserted genes.

Less than 0.1 per cent of the total DNA volume in GM plants is at all different from the DNA of the conventional parent varieties. There is no indication in the scientific literature, according to the Ministry of Agriculture researchers, that these new DNA segments or the new proteins behave any differently during digestion in the digestive tract than those from conventional plants: absorbed DNA and proteins are quickly broken down in the digestive tract by gastric acid and microbial activity. In some pre-treated feedstuffs like silage maize, a large part of the DNA and proteins is destroyed during the ensiling process through heat or extraction.

Even when isolated DNA segments survive the pre-treatment or the digestion in the digestive tract, findings from scientific studies shows that various mechanisms within the animal and human body ensure that these gene segments cannot become active. Firstly, the promoters in the consumed plant DNA which switch the genes on and off do not work in human and animal cells. This means that the genes cannot be activated. Secondly, the body is able to recognise foreign DNA segments and get rid of them.

The study authors are: Prof. Dr. Gerhard Flachowsky, Dr. Hartwig Böhme, Dr. Ingrid Halle (FAL, Institute of Animal Nutrition), Dr. Karen Aulrich (FAL, Institute of Organic Farming); Dr. Frei Schägele (Federal Research Centre for Nutrition and Food), Hermann Broll (Federal Institute for Risk Assessment)