Those genes make a small but important difference to the way these pigs process their food.
Ordinarily, pigs cannot easily digest chemicals called phosphates. That means that the stuff that comes out of the back end can be toxic and damaging to the environment. The phosphates are easily washed into waterways, where they can produce a hugely fertile environment for plants. But the plants grow so rapidly that they choke the stream or river and cause huge damage to the ecosystem.
The genetic modification enables these pigs to digest phosphates, which means they are less polluting and cheaper to feed.
Jeremy Cooke of BBC News has more: Link |Photo by Flickr user thornypup used under Creative Commons license