Pigs have trouble fully digesting a phosphorus-based compound known as phytate found in many cereal grains used to feed them. Thus, they must be given phosphorus-enriched food supplements. Both the phytate and the excess phosphorus from supplements end up concentrated in the animal’s manure. This is then used as fertilizer for various crops. This would not be a problem except that the excess phosphorus leaches into the soil and rain washes out much of the energy-rich substance into ponds, lakes, rivers and streams. This leads to eutrophism or hypertrophism of the algae in these water ways, which can ultimately choke most of the life in them.
But now comes ‘Enviropig’. Thanks to transgenic technology, a favorable gene from one animal can be inserted into the DNA of another, commercially valuable animal, resulting in a hybrid that exhibits more favorable traits (in this case a “cleaner and greener” pig breed). This has been done with goats that produce spider silk in their milk, but the enviropig is one of the first created in direct response to concerns over environmental impacts.
University of Guelph scientists have created a transgenic pig — the Enviropig — which better digests phosphorus compounds. This development came in response to concerns of negative environmental impacts from animal manure run-off causing algal blooms in waterways, and consequently killing fish and other aquatic creatures.
An estimated 50 – 75 percent of the phosphorus in livestock feed (grains, corn, soy) is in the form of phytate. Phytate is a more stable and complex phosphorus compound (produced naturally in these feed plants) and normal pigs are not able to digest it completely. The result of this incomplete digestion is that more phosphorus ends up in the pig’s manure which is subsequently used as fertilizer. Both soil leaching and fertilizer run-off allow much of this to enter streams, ponds and other waterways–polluting them with algal over-growth and depriving the water of oxygen (this also happens from land run-off into marine systems).*
In response to growing concerns over manure-based, fertilizer run-off creating anoxic (no oxygen) conditions in fresh water habitats, researchers at the University of Guelph, in Ontario Canada, have taken a gene from the E. coli bacterium– one that codes for the phytase enzyme that breaks down phytate — and inserted it into the genome of a breed of Yorkshire pigs. The result is a pig with a normal growth rate, but which eats less food, produces less waste, has less phytate excreted in the manure (30 – 65% less) and thus less phosphorus in land run-off to pollute local waterways and resources.
Health Canada has certified that the transgenic pig does indeed digest more phytate and does not have a negative environmental impact. Currently, the University is seeking approval from Health Canada and the US FDA stating that the pig is safe for human consumption.
* This anoxic effect occurs when, as algae die, aerobic bacteria begin decomposing the dead algal cells. This process requires oxygen, and so, excessive decomposition of algae removes most if not all of the oxygen from the water. Once this happens, fish and many other invertebrates are deprived of oxygen and die off.
diagram: enviropig – courtesy of University of Guelph, Ontario, Canada