How can we solve the problem of pig manure?
Genetic engineering could help.
The bodily waste that pigs produce contains high levels of chemicals that can damage the environment, such as nitrogen and phosphorus. For example, when excessive amounts of these two compounds make their way into the water, they can cause blue-green algae to grow too much, which asphyxiates other life in the water.
Pigs produce a lot of nitrogen and phosphorus because they cannot efficiently digest their food. In particular, the animals lack the enzymes required to break down two types of molecules present in their feedstuff: phytates and non-starch polysaccharides (NSPs).
Zhang, Li et al. take four microbial genes which code for the enzymes needed to digest NSPs and phytates, and they add these DNA sequences into the genomes of pigs. The animals then produce enzymes in their saliva that transform NSPs and phytates into molecules which can be used by their digestive system. The pigs thus get more energy from their food, and they grow faster and bigger. They also produce less nitrogen and phosphorus in their waste.
Over 1.2 billion pigs are farmed each year, and they are the most economically important meat source in the world. Raising animals that can digest their food better would reduce the need for pig feed, increase productivity and reduce environmental pollution. However, discussions with policymakers and with the public will be necessary before these results can be adopted by the farming industry.
To find out more
Read the eLife research paper on which this eLife digest is based:
