Researchers create low-pollution pigs

Scientists from the University of Guelph in Ontario have developed 33 transgenic ‘enviropigs’, whose bodies can absorb a normally indigestible form of phosphorus, reducing their fecal phosphorus levels to between 56 and 75% lower than that of regular pigs. According to microbiologist Cecil Forsberg, involved in the project, the ‘enviropig’ is the first transgenic farm animal with “enhanced production characteristics” that has not exhibited some debilitating traits, and is “for sure, the first modified farm animal engineered to solve an environmental 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. This gene was then 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 researchers monitored both transgenic and non-transgenic pigs at various stages of growth, with both sets of animals being 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. Results showed that the enzyme was present in the salivary glands but not in other tissues. According to Forsberg, the outcome exceeded the researchers’ expectations of a fecal phosphorous reduction of between 20 and 50%.

The next step, Forsberg says, is demonstrating that the animals are safe to eat and conform to Canadian governmental standards. The ‘enviropigs’ also have the potential of saving farmers money on phosphorus supplements and through an improved utilisation of minerals, proteins and starch in the diet.

“The fact that phosphorus levels were reduced in the pigs shows that the gene is working,” co-researcher John Phillips, a molecular biologist, 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.”