There is nothing new about selective breeding. Humans have always encouraged crossing between the best animals and between different breeds possessing individual characteristics they wanted to combine for food and agriculture.

The use of reproductive biotechnology in animal breeding is also not new. Artificial insemination has been around for 50 years. And with animals, as with fish and crops, there are forms of genetic manipulation already in use that do not involve direct modification of the genes.

“Embryo transfer from an excellent ewe is a case in point,” says Keith Hammond, FAO’s senior officer on animal breeding. “This is a form of genetic manipulation, and it’s certainly biotechnology.” Embryo transfers are now common, with 440 000 recorded in cattle alone in 1998.

Improving animal productivity, reducing disease

But now genetic engineering is coming to animal breeding. Its obvious uses will be to increase milk, meat and egg production and to improve disease resistance, efficient use of feed and tolerance of harsh environments – in fact, those qualities that farmers have sought from their animals for millennia.

However, the earliest applications may be animals that produce non-food items. For example, plans are under way to introduce a gene into sheep to make the udder secrete a silk protein from which spider silk can be made. Immensely fine and strong, it can be used for such benevolent purposes as surgical sutures. It may also soon be possible to modify animal organs so they can be transplanted into humans. And animals may be able to produce compounds needed for vaccination and treatment.

Special challenges

A barrier to adoption of transgenic animals, compared to food crops, is their much longer reproductive cycles, which makes research a much slower process. Moreover, the patterns of genes that scientists must identify and transfer are far more complex than those in plants. Genetically modified animals will take longer to reach production than crops and fish.

One obvious implication of genetic modification is the ethical treatment of animals. Farming is an industry already much criticized for its treatment of animals. And early attempts to produce transgenic animals resulted in physiological anomalies, weakness and impaired health and reproductive performance.

However, techniques have improved, and transgenic animals may be no more likely to suffer from distressing birth defects than ordinary ones. This is because the control inherent in genetic engineering is more apt to reduce the likelihood of birth defects among offspring of animals carrying damaging recessive genes. This will not reassure those who believe that ‘designer’ animals are simply wrong. But genetic techniques should not necessarily be associated with animal suffering.

The health question

Genetic engineering has potential benefits for animal health – for producing vaccines and antibodies and for conferring resistance to disease. Aside from the distress illnesses cause to the animal, disease does appalling economic damage, especially in poor communities that depend heavily on livestock. The implications for food security are enormous.

“Over the last 15-20 years, US$ 100 million has been spent on attempts to control African swine fever,” says FAO virologist Peter Roeder. “They’ve failed. Do we go on spending, or do we try new methods?”

The impact of modern biotechnology on animal health falls into three categories:

• Diagnostics, such as the development of molecular kits to diagnose animal diseases. It is now possible to analyse gene sequences of microbes and parasites, allowing rapid and accurate diagnosis of the exact type.

• Vaccines. Recombinant vaccines – those developed through gene manipulation – can be highly effective. A recombinant rabies vaccine is already widely and successfully used in Europe and the United States. Now several groups of researchers in the United States and the United Kingdom are working on marked recombinant vaccines for rinderpest to help in discriminating between wild virus infection and vaccination.

• Epidemiology, the study of the spread of diseases. Organisms such as viruses evolve and mutate very quickly, and so do their behaviour and resistance. From the sequence of an organism’s genes, it is possible to understand how and where it evolved – a process known as phylogenetics. This can show how the organism is evolving now and what it will do next, helping to identify the right vaccines for combating fast-evolving viruses such as foot-and-mouth disease.

Genetic markers can now be inserted into vaccines, so that workers in the field can distinguish between animals that have a disease and those that have simply been vaccinated. This means that vaccinated animals won’t have to be destroyed on suspicion of being disease carriers. And genetic markers are also about to become important in food safety monitoring. For example, it will soon be possible to detect foreign proteins in foodstuffs quickly and cheaply.

The use of genetic engineering to modify animals is bound to be controversial. In particular, the arguments about ethics and animal welfare will be fierce – and will cut both ways.

March 2003