© JOEL HOLLAND
In the mid-1990s, microbiologist Cecil Forsberg of the University of Guelph in Ontario and his colleagues thought they’d achieved a pig production breakthrough: they had genetically engineered swine that could digest the phosphorous compounds in their feed. Phytase, an enzyme that breaks down phosphorus-containing phytate in plants, is produced by the gut bacteria of cows and other ruminants, but it is not made by pigs. Forsberg’s team borrowed a phytase gene from E. coli and a fragment of mouse DNA that mediated the enzyme’s production in the salivary glands, injected the genetic construct into pig zygotes, then inserted those zygotes into fertile sows. “In the end, we had approximately 30 different lines of pigs,” Forsberg recalls. The researchers screened the animals for levels of phytase ...
