Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
July 31, 2001
U of G's 'enviropig' a success, new study reveals
A first-ever study of the University of Guelph’s “enviropigs” confirms what researchers predicted all along: the animals produce manure that is more environmentally-friendly, containing up to 75 per cent less phosphorus.
The findings of molecular biologist John Phillips, microbiologist Cecil Forsberg and graduate student Serguei Golovan will appear in the August 1 issue of Nature Biotechnology. The researchers studied 33 lines of “enviropigs,” pigs that they genetically modified so their bodies can absorb a normally indigestible form of phosphorus. The scientists discovered that enviropigs have fecal phosphorus levels that are 56 to 75 per cent lower than that of regular pigs.
“It has exceeded our expectations,” Forsberg says, adding the researchers had hoped for a fecal phosphorous reduction of between 20 and 50 per cent. “It would be difficult for anyone to improve on it – not bad for a first attempt.”
The scientists created the first three Enviropigs – named Wayne, Jacques and Gordie after Canadian hockey players – two years ago. “Their offspring were key parts of this study,” Forsberg adds. The enviropig is believed to be the first transgenic farm animal with “enhanced production characteristics” that has not exhibited some debilitating traits, Forsberg said. “It is, for sure, the first modified farm animal engineered to solve an environmental problem.” Animal waste is a leading source of phosphorus pollution from agriculture. This arises because phytate phosphorous, the major form of phosphorus in cereal grains, is not digested and is instead excreted in fecal materials by pigs and other animals. Phosphorus pollutes surface and groundwater and promotes the growth of algae in rivers, lakes and streams, reducing available oxygen to fish and aquatic life.
To correct this problem, the researchers combined an E. coli gene that makes the enzyme phytase and a small portion of a mouse gene that controls the production of a protein secreted in the salivary glands to make a new composite gene. The composite gene was inserted into the nucleus of a one-celled pig embryo with a microscopic needle, and the embryos were then surgically implanted in a foster mother. The gene allows the pig to make phytase in the salivary gland and secrete it into its saliva, where it is swallowed with food. The phytase releases phosphate in the animal’s gut that can be absorbed by the bloodstream.
“The fact that phosphorus levels were reduced in the pigs shows that the gene is working,” Phillips said. “This has proved that producing farm animals with the same gene is a plausible and promising biological approach to creating more sustainable animal agriculture.”
The researchers monitored both transgenic and non-transgenic pigs at various stages of growth. The animals were fed standard diets with and without supplemental phosphorus, and then comparisons were made in fecal phosphorus levels. Tests were also conducted on the saliva and tissues of both transgenic and non-transgenic pigs to determine the phytase enzyme amount in various tissues. The results showed that the enzyme was present in the salivary glands but not in other tissues.
This is the second animal in which the composite gene has proven successful. In May, the researchers published a paper in the same magazine, reporting that in tests on mice models, the gene also showed a significant decrease in fecal phosphorus. The next step, Forsberg said, is demonstrating that the animals are safe to eat. Such studies will be subjected to the Novel Food Guidelines imposed by Health Canada, he said. The enviropigs also have the potential of saving farmers money. “This novel trait is expected to eliminate the need to supplement the diet with phosphorus for up to $1.70 per pig,” said Clare Schlegel, chair of Ontario Pork, which helped fund the research. “Additional benefits may include improved utilization of minerals, proteins and starch in the diet.”
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