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Enviropig is the trademark for a genetically modified line of Yorkshire pigs, with the capability to digest plant phosphorus more efficiently than conventional unmodified livestock pigs, that was developed at the University of Guelph.[1] The benefits of the Enviropig if commercialized include reduced feed cost and reduced phosphorus pollution[2] as compared to the raising of conventional pigs.

Background and development[edit]

Enviropigs produce the enzyme phytase in their salivary glands. When cereal grains are consumed, the phytase mixes with food in the pig's mouth, and once swallowed the phytase is active in the acidic environment of the stomach degrading indigestible phytic acid with the release of phosphate that is readily digested by the pig.

Cereal grains including corn, soybean and barley contain 50 to 75% of their phosphorus in the form of phytic acid. Since the Enviropigs can now digest phytic acid, there is no need to include either a mineral phosphate supplement or commercially produced phytase to balance the diet. Because no phosphorus is added to the diet and there is digestion of the phytic acid, the manure is substantially reduced in phosphorus content, ranging from a 20 to 60% decrease depending upon the stage of growth and the diet consumed.

The Enviropig was developed by the introduction of a transgene construct composed of the promoter segment of the murine parotid secretory protein gene and the E. coli phytase gene.[2] This construct was introduced into a fertilized embryo by pronuclear microinjection, and this embryo along with other embryos was surgically implanted into the reproductive tract of an estrous synchronized sow. After a 114-day gestation period, the sow farrowed and piglets born were checked for the presence of the transgene and for phytase enzyme activity in the saliva. Through breeding, this line of pigs is in the 10th generation, and the phytase trait is stably transmitted in a Mendelian fashion.

An editorial entitled "Genetically engineered meat close to your table" was published with online video and audio explaining the digestive capability of the Enviropig.[3]

Environmental impact[edit]

Approximately 50-75% of the phosphorus present in cereal grains, corn, and soybeans is present in an indigestible compound called phytate that passes through the pig digestive tract and is enriched in the manure approx. 4-fold because the protein and carbohydrates in cereals are digested and absorbed. When manure from conventional pigs is spread on land in areas of intense swine production, there is a buildup of phosphorus in the soil. During spring run off or during a heavy rain, the phosphorus may leach into ponds, streams, and rivers increasing the phosphorus content, an essential nutrient for algae growth. With an excess of phosphorus there is increased algal growth that eventually causes a reduction in oxygen concentration in the water that results in the death of fish and other aquatic animals. This process is known as eutrophication. Often toxins are produced by the algae and the water is no longer safe to drink. Since the Enviropigs excrete less phosphorus in the manure, there is less opportunity for pollution of water sources.

In 1940 the food system produced 2.3 calories of food energy for every calorie of fossil-fuel energy used in production. The energy cost included all aspects of production and delivery. In 2008 only one calorie of food energy at the supermarket was produced for every 10 calories of fossil-fuel energy used in production.[4] The Enviropig is an example of how to reduce the energy requirement for meat production by eliminating the feed additive phosphorus.[citation needed] The reduction in phosphorus demand is also important due to peak phosphorus.


Cathy Holtslander, community organizer with Saskatchewan-based Beyond Factory Farming, says an alternate way to address the problem of phosphorus pollution would be to reduce the concentration of hog-confinement facilities and the numbers of animals in them. She stated: "The problem isn't with the pigs. The problem of hog operations polluting the water has to do with the whole industrialization scale that has been developed to raise hogs."[5]

Regulatory requirements[edit]

On February 20, 2010 the Department of the Environment of the Canadian Government determined that Enviropig is in compliance with the Canadian Environmental Protection Act and can be produced outside of the research context in controlled facilities where they are segregated from other animals.[6] Steven Liss, associate vice-president (research services) of the University of Guelph said in February 2010 that "Applications to other federal agencies to assess the safety of Enviropigs for human food and animal feed were currently under review both in the U.S. and Canada and there is no set date when or if these reviews will conclude."[7]

United States Food and Drug Administration (FDA) has a Guidance Document that outlines types of data needed to assess food and environmental safety of a genetically engineered (GE) food animal:[8]

  1. Product identification/description.
  2. Molecular characterization of the genetic construct introduced into animal.
  3. Molecular characterization of the GE animal lineage.
  4. Phenotypic (physiological) characterization of the GE animal.
  5. Stability of the new inheritable trait through generations.
  6. Food, feed and environmental safety.
  7. Effectiveness of the new trait/claim validation.
  8. Post-approval responsibilities.

The FDA guidance document is consistent with the United Nations Codex Alimentarius Commission regulatory guidance.[9]

Regulatory approval of the Enviropig will be required in any country[citation needed] before commercialization of these pigs for human food consumption.

Loss of funding[edit]

Ontario Pork ended its support for the Enviropig program in April 2012.[10] The University of Guelph killed the pigs, from the 10th generation of the project, in June 2012 after it couldn’t find a new partner to fund the project.[11] However, the genetic material will be stored at the Canadian Agricultural Genetics Repository Program.

See also[edit]


  1. ^ Cooke, Jeremy GM pigs: Green ham with your eggs? BBC News US & Canada, 4 January 2011, retrieved 5 January 2011
  2. ^ a b Golovan SP, Meidinger RG, Ajakaiye A, et al. (August 2001). "Pigs expressing salivary phytase produce low-phosphorus manure". Nature Biotechnology. 19 (8): 741–5. doi:10.1038/90788. PMID 11479566.
  3. ^ Ogilvie, Megan (22 November 2008). "Genetically engineered meal close to your table". Toronto Star. Retrieved 15 July 2009.
  4. ^ Pollan, Michael (9 October 2008). "Farmer in Chief". The New York Times. Retrieved 15 July 2009.
  5. ^ Delaney, Joan (23 February 2010). "Will This Little Piggy Go To Market?". The Epoch Times. Archived from the original on 1 March 2010. Retrieved 25 February 2010.
  6. ^ Significant New Activity Notice No. 15676 Vol. 144, No. 8, 20 February 2010, Canadian Government Notices, Department of the Environment, Canadian Environmental Protection Act 1999, Retrieved 5 January 2011
  7. ^ Enviropig Moves Ahead 19 February 2010, University of Guelph Campus Bulletin, Retrieved 5 January 2011
  8. ^ "Genetically Engineered Animals". Fda.gov. Retrieved 2010-08-19.
  9. ^ Guideline for the Conduct of Food Safety Assessment of Foods Derived from Recombinant-DNA Animals; in ALINORM 08/31/34, Appendix II; ftp://ftp.fao.org/codex/Alinorm08/al31_34e.pdf
  10. ^ Leung, Wendy. University of Guelph left foraging for Enviropig funding, The Globe and Mail, Apr. 2, 2012. Accessed July 31, 2012.
  11. ^ Schimdt, Sarah. Genetically engineered pigs killed after funding ends, Postmedia News, June 22, 2012. Accessed July 31, 2012.

Further reading[edit]

External links[edit]