Pigs – photo from Wikimedia Commons
In short, no. However, it may be able to reduce the carbon footprint of the pork industry. You’re probably wondering what in the world pig manure has to do with climate change. Trust me, I was in the same position before embarking on some research of my own.
Piles of pig manure – photo from Geograph
Apparently pigs lack 3 important enzymes needed to digest the nitrogen and phosphorus in their feed. Nitrogen oxide, a dangerous climate pollutant, is thus released from the manure of these animals. Although it only makes up about 6% of all US greenhouse gas emissions, it can trap 300 times as much heat as carbon dioxide, according to EPA. Reducing nitrous oxide emissions could play a major role in reversing the effects of global warming.
2016 U.S. nitrous oxide emission, by source – Data courtesy of EPA
5% of nitrous oxide emissions are a result of manure. To tackle this source, scientists began looking into finding a way to enhance the digestion of feed in pigs in order to reduce the excretion of dangerous pollutants. Xianwei Zhang and colleagues at the South China Agricultural University considered genetically modifying their pigs to be better able to digest these nutrients. The findings, which were published in eLife, proved that the new generation of transgenic pigs did in fact release less nitrogen.
So how exactly were the pigs genetically engineered?
Diagram depicting the process of Somatic Cell Nuclear Transfer on a sheep – photo from Wikimedia Commons
Firstly, the scientists looked at what pigs lacked to know what to modify. The enzymes that pigs needed for the digestion of nitrogen were b-glucanase, xylanase and phytase. Zhang and researchers attempted introducing genes required to make these enzymes into the genomes of the pigs by a process called Somatic Cell Nuclear Transfer, or more simply, cloning. The image to the left outlines the key steps.
Next, they determined how to make the digestion process as efficient as possible. By expressing the 3 bacterial enzymes in the animals’ salivary glands, they were able to ensure that digestion began in the mouth.
Now comes the unpleasant part. In order to test their methods, the team was required to measure nutrient levels in the pigs’ manure and urine. That’s right, they studied poop!
As predicted, fecal nitrogen outputs in the modified pigs were reduced by as much as 45.8%. The scientists also noted that due to an increase in nutrient digestion, the pigs were becoming fully grown a month earlier than their non-genetically modified peers.
By growing fast, requiring less food and producing fewer pollutants, the pigs developed by Zhang and her team could lead to a win-win situation for farmers and the environment. Now imagine the benefits if we apply similar methods to major sources of agricultural greenhouse gas emissions, such as cows and sheep!
