Effects of Genetically Modified Animal Feeds

A picture of cattle in the field.

Animal feeds frequently contain genetically modified crops and enzymes derived from genetically modified micro-organisms. Feed Mixtures are mainly used for poultry, pigs and dairy cows and are formulated from a range of raw materials, including maize and other cereals and oilseeds such as soybeans and canola-a plant developed using traditional plant breeding techniques by Canadian plant breeders to remove the anti-nutritional components (erucic acid and glucosinolates) from rapeseed to assure its safety for human and animal consumption.It is currently estimated that 51 percent of the global area of soybeans, as well as 12 percent of canola and 9 percent of maize (used as whole maize and by-products such as maize gluten feed) is genetically modified (James, 2002a).

Safety assessment studies in many countries have compared the new genetically modified feeds with their conventional counterparts. Considerations include the effects on the animal eating the feed and on consumers eating the resulting animal product, worker safety and other environmental aspects of using the feed. In addition, comparisons of nutritional composition and wholesomeness between animal feeds containing transgenic versus conventional components have been the subject of many studies.


The major concerns associated with the use of GM products in animal feeds are whether modified DNA from the plant may be transferred into the food chain with harmful consequences and whether antibiotic-resistance marker genes used in the transformation process may be transferred to bacteria in the animal and hence potentially into human pathogenic bacteria. As the production process for the enzymes used in animal feeds takes place under controlled conditions in closed fermentation tank installations and eliminates the modified DNA from the final products, these products do not pose any risk to the animal or the environment.

Researchers have examined the effects of feed processing on DNA to ascertain whether modified DNA remains intact and moves into the food chain. It has been found that DNA is not fragmented to any great extent in raw plant material and silage, but remains partially or fully intact. This means that, if GM crops are fed to animals, animals would be likely to be eating modified DNA. In order to consider whether modified DNA or derived proteins consumed by animals have the potential to affect animal health or to enter the food chain, it is necessary to consider the fate of these molecules within the animal. Digestion of nucleic acids (DNA and ribonucleic acid, RNA) occurs through the action of nucleases present in the mouth, the pancreas and intestinal secretions. In ruminants, additional microbial and physical degradation of feed occurs. Evidence suggests that more than 95 percent of DNA and RNA is completely broken down within the digestive system. In addition, research carried out on the digestion of transgenic proteins in vitro culture has shown nearly complete digestion occurring within five minutes in the presence of the enzyme pepsin.

Also no adverse effects have been reported on either growth, body-weight, feed conversion, nutrient composition, or milk production in animals fed on transgenic products.

It may be concluded that the risks to human and animal health from the use of GM crops and enzymes derived from genetically modified micro-organisms as animal feed are negligible. Nevertheless, some countries do require labelling to indicate the presence of GM material in imports and products derived thereof