We’ve all heard it, “Pork, the other white meat.” It’s an ad campaign as ubiquitous as, well, pork. According to the National Pork Producers Council, pork at 42.6 percent, is the world’s most widely eaten meat. And while pork is popular, hog farms can sometimes cause environmental problems. Until now…Move over conventional hogs, and enter the EnviropigTM.
The saliva of EnviropigTM contains the enzyme phytase, which allows the pigs to digest phytate, the principal form of phosphorus, in their diet. Without phytase, the phosphorus passes though undigested to become the single most important pollutant in pig manure. Phosphorus run-off from fields spread with manure on flowing into ponds and streams leads to extensive algal grow, which can be a human health hazard. To develop the EnviropigTM Cecil Forsberg and his colleagues at the University of Guelph in Ontario, Canada had to find a stable form of the enzyme phytase, with high activity in acidic conditions. The scientists found their enzyme in Escherichia coli, a bacterium commonly found in the hindgut of many animals, including humans. The scientists had to figure out how to insert the phytase gene into the pig and have it be expressed in the correct place. After all, having the phytase gene in the pig, but having it expressed in the tail, would be completely useless since the phytate problem is in the digestive tract and not the tail.
To get the gene expressed in the correct place, the scientists needed to find a directive switch to which the gene is connected. That is, a switch, or what scientists call a promoter, that would turn on the gene at the right time and in the right place in the pig. Forsberg and his team found that the promoter that worked best was from the mouse, the mouse constitutive parotid secretory protein promoter.
Forsberg and his colleagues then injected both genes into pig embryos. The injected pigs did express the trait, that is, they secreted phytase in their saliva. Of the transgenic pig embryos, the ones showing the highest levels of phytase activity were selected for breeding. This trait has now been bred through seven generations of pigs. This is an exciting advancement in animal biotechnology but there are some important things to remember:
- Phytase activity is not found in any of the meat cuts or other major food tissues such as the liver and kidneys of the pig.
- The mouse promoter does not make any protein product and only serves as a DNA on-off switch.
- The gene that makes the phytase, comes from E. coli. But this doesn’t mean the pork will contain E.coli, scientists are only using the gene – not the bacteria! Humans have E. coli in their guts, and likely have phytase as well.
All of this means that we can conserve the environment and have our meat too, in a way that would have been impossible without biotechnology.