Genetically modified organisms: consequences for ruminant health and nutrition

Abstract

-Many of the plants eaten by farmed ruminants are capable of being genetically modified, and may in the future be modified for nutritional, agronomic or industrial purposes. Techniques are also becoming available for genetic modification of silage and ruminal bacteria. Those working in agricultural biotechnology have a clear responsibility to detect and avoid any unintended or undesirable consequences of such modifications, whether direct or indirect, upon the animal, the consumer and the environment. One of the most general concerns that has been expressed is the possibility for onward transfer of modified gene sequences to gut microorganisms or host cells. Rare acquisition of diet-derived DNA fragments cannot be ruled out, but if this occurs, it must have also occurred throughout mammalian history. The possible impact of genes not normally present in ruminant diets must, however, be considered. Discussion of the use of antibiotic resistance markers in transgene constructs must take into account the wider debate on the likely impact of antibiotic use in animal agriculture on the spread of antibiotic resistant bacteria. There is increasing evidence that overuse of antibiotics has lead to extensive transfer of antibiotic resistance genes between bacteria from the human and animal gut. In general this is likely to have a far greater impact than any rare transfer events involving resistance genes passing from transgenic plants to microbes. Our rapidly improving ability to use sophisticated molecular approaches to predict and track the consequences of genetic modification will help to ensure safe application of GM technology in agriculture in the future. GMO / rumen / ruminant nutrition / gene transferRésumé -Organismes génétiquement modifiés : conséquences pour la santé et la nutrition des ruminants. La plupart des plantes actuellement consommées par les ruminants d'élevage peut être -ou est déjà -manipulée génétiquement, et il est probable que ces plantes seront encore modifiées dans le futur pour améliorer leurs propriétés nutritionnelles, agronomiques ou technologiques. Par ailleurs, il est maintenant techniquement possible de modifier génétiquement les ferments d'ensilage ou les bactéries du rumen. Les chercheurs impliqués dans ces biotechnologies doivent donc être capables Ann. Zootech. 49 (2000) 255-271 255

The role of conjugative transposons in spreading antibiotic resistance between bacteria that inhabit the gastrointestinal tract

“…Consequently, it may be preferable to carry out the manipulation and reintroduction simultaneously on more than one bacterial strain. In the case of rumen bacteria, manipulations have been aimed at improving plant fibre degradation, and ultimately animal production [reviewed by e. g. 55,56]. Despite the fact that ruminants and their bacterial symbionts have coevolved over thousands of years, recent changes in farming practices mean that the resident bacterial population is no longer optimal to provide maximal energy release from the feed provided.…”

Protein nutrition for ruminants in European countries, in the light of animal feeding regulations linked to bovine spongiform encephalopathy

“…In recent years, several of the plant species used as ingredients of animal feeds have been subject to genetic modifications (GM) operated by recombinant deoxyribonucleic acid (DNA) technology. Among the crops concerned by GM-induced tolerance to various herbicides or resistance to insects or viruses (21), soybean and rapeseed are currently used to a large extent as protein sources in concentrates fed to ruminants in countries in Europe. Table III shows the situation in 2001 in France regarding the ingredients incorporated into manufactured concentrates fed to dairy cows and beef cattle.…”

Biotechnology, genetic conservation and sustainable use of bioresources

“…Since then, many transgenic farm animals have been produced on a routine basis. Examples are transgenic fish that grows 2-3 times faster than normal and is cold-tolerant was produced by microinjection of desired DNA into oocytes, transgenic cattle, sheep, swine and rabbits produced by microinjection of desirable gene into zygote to produce faster-growing animals with better meat quality, transgenic goats and sheep which produce human milk because of the transfer of human genes into such animals, and transgenic chicken which grow faster and are tolerant to viral diseases because of the transfer of growth hormone gene as well as a gene that increases viral resistance based on interference (Bazer, 1992;Fox, 1992;Forano and Flind, 2000).…”