by Alicia M Prater PhD

Created on: August 30, 2010

Pig waste is a problem for both farmers and the environment. Pigs are unable to digest phytate, a phosphorus compound that makes up 50 to 75 percent of the phosphorus content of the grains and plants eaten as dietary staples by these animals. The phytate is then excreted in the pig waste, contaminating agricultural areas via run-off and drainage. Major fish kills, including that of 10 million fish in North Carolina in 1995, have been blamed on hog manure. From 1995 to 1998, 1000 manure spills in 10 states were estimated to kill 13 million fish. The excess phosphorus in the pig waste is also linked to toxic algal blooms in waterways (

NRDC). In addition, the pigs then require additional dietary phosphorus to make up for what they could not digest, creating an economic burden on farmers. Researchers at the University of Guelph have attempted to find a solution to these problems – and they’re calling it Enviropig.

Enviropig is a transgenic Yorkshire pig that contains the E. coli gene for phytase, bestowing the pigs in this strain with the ability to digest phytate. The enzyme is produced in their saliva and remains active in the pig’s stomach, aiding in digestion throughout the process. The transgenic pigs excrete 30 to 65 percent less phosphorus waste than normal pigs. However, the pigs are normal in every other way. Simply put, this is a breed of cleaner pigs – they require less, if any, phosphorus supplementation and reduce agricultural contamination.

The University owns all rights to the Enviropig and is still in the approval process for agricultural and commercial use. Since 2007, the risk of the transgenic pig to the environment and the safety of the pig for human consumption has been the subject of studies. Canada has approved the claims made by the University about Enviropig’s function and environmental safety of the animal, but human consumption studies and the agreement of the United States on both issues may take a few more years to finish (TheScientist).

Concern likely mainly lies in the presence of the phytase gene in the meat, but it’s only a precautionary measure. The enzyme is already fed directly to pigs in a form that acts nearly identically to the secreted phytase in Enviropig, so the only difference in these pigs is its source. Also, a single gene from E. coli does not equate with the presence of the bacteria in the animals – there is theoretically no increased risk of contamination or infection. However, a mystique still exists in regards to genetic engineering and transgenic animals, making many worried about unknown effects from human consumption despite the great benefit this animal offers.

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