Enviropig is the trademark for a genetically modified line of Yorkshire pigs, with the capability to digest plant phosphorus more efficiently than conventional unmodified pigs, that was developed at the University of Guelph. The benefits of the Enviropig if commercialized include reduced feed cost and reduced phosphorus pollution as compared to the raising of conventional pigs.
Background and development
Enviropigs produce the enzyme phytase in their salivary glands. When cereal grains are consumed, the phytase mixes with feed 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. 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.
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. 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. The Enviropig is an example of how to reduce the energy requirement for meat production by eliminating the feed additive phosphorus. 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."
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. 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."
- Product identification/description.
- Molecular characterization of the genetic construct introduced into animal.
- Molecular characterization of the GE animal lineage.
- Phenotypic (physiological) characterization of the GE animal.
- Stability of the new inheritable trait through generations.
- Food, feed and environmental safety.
- Effectiveness of the new trait/claim validation.
- Post-approval responsibilities.
The FDA guidance document is consistent with the United Nations Codex Alimentarius Commission regulatory guidance.
Regulatory approval of the Enviropig will be required in any country before commercialization of these pigs for human food consumption.
Loss of funding
Ontario Pork ended its support for the Enviropig program in April 2012. 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. However, the genetic material will be stored at the Canadian Agricultural Genetics Repository Program.
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