A less polluting pig.

A Less Polluting Pig There's good news in the fight against farm pollution, say researchers in the Department of Molecular Biology and Genetics at the University of Guelph in Ontario, Canada. In August, John Phillips, Cecil Forsberg, and Serguei Golovan announced a new kind of pig that makes better use of phosphorus, a nutrient that in high concentrations can deplete oxygen levels in waters downstream. Phosphorus runoff from livestock farms has been blamed for killing aquatic life and creating algae blooms in lakes and rivers. By identifying a gene that promotes recovery of phosphorus in a pig's digestive tract, Phillips and his colleagues say they have devised a pig that pollutes less. Genetic engineering in foods has become common in the past few years. Initial widespread breakthroughs came with pest-resistant grains. Since then, scientists have explored genetic modification of milk cows, fish, and other animals for improved food production. With the enviropig (as the Guelph researchers have dubbed their porker), genetic engineering is being used to fight in a new environmental arena: reduced pollution production. For Phillips, a professor of molecular biology and genetics, phosphorus waste was an obvious focus for swine research. Farmers like to use hog manure as fertilizer because it is rich in nutrients, but because pigs cannot completely digest the phosphorus in their diet, their manure contains much higher concentrations of phosphorus than of other nutrients. When runoff carries the manure downstream, the excess phosphorus fuels extremely high algae growth. "It's not just a local problem, it's an international problem," Phillips says. To reduce the phosphorus concentrations in hog manure, the researchers looked for an enzyme that could break down the element in the digestive tract. They found a phytase enzyme in a strain of Escherichia coli bacteria (although E. coli is found in the intestinal tract, it appears too late in the digestive process to handle phosphorus). The phytase could survive the chemical rigors of digestion and proved very active in acidic conditions; that meant it could break down the phosphorus in feed grain in a pig's stomach before it reached the intestine. The researchers then spliced the enzyme with a genetic "directional trigger" from mice that would target the enzyme to the salivary glands. The fused gene (or transgene) was tested first in mice to make sure the phytase appeared only in the salivary glands and would not otherwise affect an animal's health. The transgene was then introduced into pig embryos. DNA and enzyme analysis confirmed that the piglets carried the gene and that their saliva contained the phytase. The pigs, now several months old, appear healthy and normal, according to Phillips. The Guelph scientists are confident that the salivary phytase will be passed to successive generations. Other efforts to reduce phosphorus runoff from livestock farms have sought to