Aug 13, 2010

Research Projects

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Feeding study: Long-term use of MON810 Bt maize in dairy cows

(2005 – 2007) Chair of Physiology, Center of Life and Food Sciences Weihenstephan, Technische Universität München

Topic

This project investigated the potential impacts on dairy cows of long-term feeding with genetically modified MON810 Bt maize. It investigated

• the health of the animals, their fertility, metabolism and milk yield,
• possible changes in the digestive tract,
• the milk quality and its components.

The project also studied the breakdown of the Bt protein and of the recombinant DNA in the feed and in the animals.

Summary

• The studies found no differences between the conventional and transgenic feedstuffs. The nutrient composition and energy content were the same, providing confirmation of their substantial equivalence.
• Feeding the cows with MON810 Bt maize over a period of 25 months had no negative impact on their performance or metabolic parameters. There was no indication that feeding the cows with Bt maize has any effect on animal health.
• At the end of the study period, neither the Bt protein nor the transgenic DNA were found in the blood, urine or milk.
• Milk from the cows fed on transgenic maize was no different from milk from cows fed on conventional maize.

Experiment description

The project was conducted in collaboration with the Bavarian State Research Centre for Agriculture (LfL) in Grub and the Chair of Animal Nutrition at Technische Universität München.

In 25 months between May 2005 and June 2007 two groups of 18 Bavarian Simmental dairy cows were fed with either MON810 Bt maize or conventional maize (isogenic check cultivar).

Nine animals in each group were replaced because of disease or infertility during the course of the trial. However, the data for all animals was taken into account in the evaluation.

Maize cultivation, harvest and feed production

Cultivation and preservation of both maize varieties took place at various locations in Bavaria under the direction of the LfL. In order to obtain feed of a uniform quality, precautions were taken to ensure that the conditions for plant development (sowing, soil, nutrient supply, harvest time) were the same for both maize lines. The maize was preserved as silage, pressed maize plants and grain maize.

Parameters

Feed quantity and nutritional value: The feed rations were sampled twice a week and the individual maize components and additives (grass silage, straw and concentrated feed mixes) once a week, and the nutritional value was measured.

Milk yield and content: The milk yield was recorded twice a week and summarised into an average per trial week. The milk protein and milk fat content levels were also measured twice a week.

Animal health and fertility: Disease data and metabolic analyses were conducted on the blood plasma and urine. The animals’ fertility was assessed based on levels of progesterone in the milk.

Measuring levels of transgenic DNA and Bt protein: Molecular biological methods (PCR and ELISA) were used to detect potential residues of transgenic DNA and Bt protein in the animals’ milk, blood and dung. Monthly samples were taken, and a urine sample was taken every two months.

Feed samples were taken every week, combined into four-weekly samples and analysed using quantitative PCR and ELISA methods.

Samples were taken from the gastrointestinal tract and internal organs of the replaced animals and of the slaughtered cows at the end of the experiments.

Results

Feed quantity and nutritional value

The maize in the feed provided around two-thirds of the total energy on average. Steps were taken to ensure that both groups received feed with the same energy and quality levels and composition. With an average daily feed intake of approx. 16 kg, the cows fed on transgenic maize consumed around 6 mg of Bt protein each day.

Milk yield and content

The milk yield in the two groups was similar across the entire trial period, as was the composition of the milk. Feeding the animals with Bt maize did not lead to any differences in feed intake or milk yield. Substantial equivalence could therefore be said to exist.

The animals’ body condition and back fat thickness were appropriate for Simmental cattle. In general, the animals in both groups had a good energy intake.

Animal health and fertility

The blood results revealed no significant differences between the two groups either at the beginning or the end of the trial.

199 treatments were carried out during the trial as a result of illness. Of these, 93 (46.7 %) were carried out on the animals that received conventional feed and 106 (53.3 %) on the animals fed on transgenic maize. The most frequent diseases (41.7 %) involved the reproductive organs. Of these, 19.6 per cent affected the conventional group and 22.1 per cent affected the transgenic group. The distribution of diseases affecting feet and limbs, the second most common type of disease requiring treatment (26.6 %), was similar.

A comparison of the fertility indicators and parameters revealed only minor differences between the animals fed on conventional and transgenic maize.

Measuring levels of transgenic DNA and Bt protein

To measure the quantity of transgenic DNA in the feed, blood, dung and milk, special DNA-extraction and PCR methods were developed and deployed.

The DNA sequence in question and the Bt protein were found in all the transgenic feed samples. Only the Bt protein was detected in the dung of these animals, but in lower concentrations.

Analyses of a total of 900 milk samples from both groups found no indications of a transfer of transgenic DNA or Bt protein to the milk. Milk from cows fed on transgenic maize is not distinguishable from milk from cows fed on conventional maize at any time.

None of the 450 blood samples provided any indication of a transfer of transgenic DNA or Bt protein to the cow’s blood or organism.

Hardly any of the urine samples contained transgenic DNA or Bt protein. A few slightly positive urine results can be attributed to them having been contaminated with dung when the samples were taken.