Could scientists also make pigs smell sweeter?
Scientists in central Canada have genetically modified pigs to produce less phosphorus in their manure.
Phosphorus from the manure of pigs and chickens is a recognised water pollutant.
The manure from the three pigs may still smell bad, but it contains approximately a quarter of the phosphorus found in conventional pig manure.
The scientists are from the University of Guelph, and their research appears in the latest edition of Nature Biotechnology.
Doctor John Phillips is one of the pig's creators. He said the spreading of manure on farms had become a serious problem for fish.
Big smell
"This phosphorous, when the manure is applied as fertiliser, actually is too high to be utilised by the crops," he said. "It therefore is left behind to leach into waterways, lakes, rivers, and streams, becoming a pollutant which promotes the growth of algae and bacteria and which consequently chokes out the growth of fish and other aquatic organisms."
Doctor Phillips said that the team of scientists utilised a transgene that confers on the pig the ability to digest phosphorus in a way normal pigs could not.
If the genetically modified pigs are approved for human consumption by the Canadian Government, and they are produced in large numbers, the scientists said that the manure's harmful effects could be reduced.
In places where thousands of pigs are reared in so called factory farms, the run off from the manure has been known to contaminate water tables.
But people who live near intensive farming operations say the most significant problem is still the smell. That is mostly produced by the nitrogen in pig manure, and the team of scientists said they might one day be able to tackle that problem too.