Genetically modified crops are an established part of global food production.

Research effort is now turning to the development of genetically modified animals.

Canadian authorities have licensed a limited production of "enviro-pigs", animals that have been genetically modified to produce less phosphorus in their faeces.

In Edinburgh, scientists have recently created the world's first genetically modified chickens with resistance to viral disease, including bird flu.

Rather than vaccinating birds (and humans) against the disease, scientists hope that genetic modification could be a mechanism to protect large production flocks from avian flu.

In America, researchers at Texas A&M University have successfully cloned a calf that's resistant to brucellosis, tuberculosis and salmonellosis.

This research is still very secretive, but, as the pressure on future food resources increases, universities and companies are slowly becoming more open about the role of genetic modification in animal production.

Presented by Sue Broom