Canadian and Danish researchers have developed GM Enviropigs, which efficiently digest dietary phosphorus and thus solve the biggest environmental problem facing hog producers.

Animals who digest dietary phosphorus in their regular diet excrete around 50% less phosphorus. Farmers use high-phosphorus pig manure for fertilizer, but it pollutes lakes and streams and promotes algae growth, and therefore many buy costly phosphorus feed supplements.

At the Canadian University of Guelph, Profs Cecil Forsberg and John Phillips, with graduate Serguei Golovan, constructed developed the GM pigs by splicing the promoter-enhancer region from a mouse salivary gland protein gene together with the enzyme phytase, which allows animals to digest phosphorus. This composite gene, designed to direct the secretion of phytase into the saliva of pigs, was first tested in mice and found to be successful.

Danish researchers from the Institute for Molecular and Structural Biology of the University of Aarhus “borrowed” a gene from the E. Coli bacteria, combined it with mouse DNA and implanted the transgene into pig embryos, which were transferred into surrogate sows.

The experiment produced 33 piglets last summer, which produce phytase in their saliva.

As well as reducing the costs for farmers, the level of environmentally hazardous phosphorus in their manure is greatly reduced, making them environmentally friendly.

Phillips and Forsberg stressed however that the real test will come this spring, when the first baby Enviropigs will be born. If these offspring carry the transgene from their parents, then the research team will test their Enviropig herd to determine how successful the pigs are at recovering phosphorus from their feed, and identify any possible side effects to the genetic modification.

By Penny Leese, correspondent