GM Pigs Smell Sweeter

cut down pollution Pig manure is a bio-hazard, but now gene scientists have created a super breed which will keep planet clean 

Robin McKie / The Observer 20may01

Scientists have succeeded in developing a bizarre new weapon in the fight against pollution: pigs that have been genetically engineered to make perfect manure.

The super porkers produce excrement that is low in phosphate and so does not cause the contamination of water supplies and the destruction of wildlife.

From now on, the pigs' reputation should be green and sweet smelling, say the super-pork creators - although this new status is likely to get a mixed reception from ecologists who view gene modification as anathema.

'People think transgenic animals are evil, but our work shows that what really matters is how you use this kind of technology,' said one of the pigs' creators, Dr Serguei Golovan, of Guelph University in Ontario.

Scientists have worried for years about the problem of phosphate pollution. The chemical is present in many fertilisers and is washed from fields and crops by rain. It contaminates streams and eventually produces harmful algal blooms in lakes.

A major source of phosphate pollution is pig manure, a popular form of 'natural' fertiliser. Phosphates are given to pigs in their food in order to boost their growth. However, most of it simply passes through their digestive system and into the soil.

In many parts of the world, the result is serious pollution. Indeed, so bad is the environmental hazard in some countries that pig farming is banned.

But now Dr Golovan and his colleagues believe they have come up with the solution: a breed of pigs that excretes phosphate-low manure. In the current issue of Nature Biotechnology, the group reveals details of their successes.

They started by isolating from a bacterium a gene that makes phytase - a naturally occurring enzyme involved in breaking down phosphates.

The group then inserted this gene into mice - who began to produce saliva rich in phytase. Boosted by this success, the researchers, led by microbiologist Professor Cecil Forsberg, repeated the trick with pigs.

The end result was a trio of piglets which also had saliva rich in phytase. 'That was very encouraging,' Dr Golovan said. 'However, getting a transgenic animal to produce a new enzyme or chemical is relatively simple. Proving that this chemical is actually working inside their bodies as you wish it to do is a different matter. Quite often an added gene makes an enzyme or protein in an inactive state. That would have been useless for our work.'

In its paper, the team reports that its first creations, genetically engineered mice, did make excrement that was low in phosphates. More importantly, the group has also carried out a two-year study of their pigs - who all passed with flying colours and with lots of excrement that had low levels of phosphate.

'We have still to publish this work, but we have now shown that we can make pigs that make manure low in phosphates and which should be a great help in cleaning up the environment. We still have some more trials to do, but in a few years, we should be able to start marketing these animals.'

Dr Golovan added that the group is also working on adding other genes to pigs, including ones that would boost their ability to process cellulose in vegetables, and stop them from producing excrement rich in nitrogen - another major source of pollution.

He said: 'Nitrogen and phosphorus are major pollutants, and if we can stop pigs producing these elements then we will help the environment - and save the pig's reputation.'