Methods of breeding transgenic animals are not yet suitable for breeding livestock because of scientists' ignorance of the key genes involved.

This message came during the Edinburgh International Science Festival from Grahame Bulfield, director of the Biotechnology and Biological Sciences Research Council's Roslin Institute.

The institute recently announced a revolutionary technique to clone sheep. Other researchers have hailed this as potentially opening the door to manipulating sheep's genes before cloning them. But despite this advance in the manipulation of genetic material, scientists are still a long way from transferring useful characteristics from one animal to another - transgenic breeding.

The BBSRC, Medical Research Council and Wellcome Centre for Medical Science were among the sponsors of a one-day conference on the technology and ethics of breeding genetically modified animals. Dr Bulfield said the commercially important traits in farm animals, such as growth, fertility and disease resistance, were controlled by many genes whose number, identity and character were still unknown.

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There were now major genome mapping programmes both in the United Kingdom and European Union, parallel to those pioneered for humans and mice, to identify and isolate these genes, he said. Many of the genes controlling commercial traits were likely to be able to be used in breeding programmes within five to ten years.

Conference convener Kenneth Boyd of the Institute of Medical Ethics stressed that while transgenics offered real opportunities of alleviating animal and human suffering, research must not be seen in isolation from public debate.

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"Experts alone can't make the decisions about how far society should go along the way of the new scientific awareness. Experts can tell us what they know about the likely benefits and risks, but deciding which risk is worth taking against the risk of not taking it raises ethical questions about what we as individuals and a society value or believe is most important," he said. "We need to think carefully so that if and when unforeseen problems arise, we don't turn on the experts and Government and say: 'This is another fine mess you've gotten us into'."