Genetically engineered animals and the FDA

An extra piece of genetic material (DNA) is inserted into the animal's genome at the earliest stages of development. Sometimes the method involves manipulating a fertilized egg that is then implanted into a surrogate mother; other times, it alters a cell from which an animal will be cloned. As the embryo grows, the DNA splice is replicated with the rest of the genetic material so that it ends up in every cell of the individual.

In fast-growing salmon developed by Aqua Bounty, the inserted gene is a salmon growth hormone, identical to the one the fish have naturally. The benefit comes from the precise placement of the added gene, which makes it active at times that the natural gene is not. "Normal salmon grow very, very slowly, and when it is cold they don't grow at all," Stotish says. "Our gene is active under a broader range of conditions and it allows the animals to grow." At 1 year old, a normal salmon might weigh 30 grams, but the transgenic fish weigh a kilogram, he says.

In pigs developed to contain omega-3 fatty acids, the added gene directs formation of an enzyme that converts naturally occurring omega-6 fatty acids to omega-3s. The gene is derived from tiny roundworms but is modified to make it more mammalian, says Randall Prather, co-director of the National Swine Resource and Research Center at the University of Missouri in Columbia, who developed these pigs.

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Why did the FDA opt to regulate genetically engineered animals in this manner and what criteria are used to assess safety?

The FDA is responsible for food safety and already regulates genetically modified crops. By considering a DNA segment a drug, the agency will regulate transgenic animals in the same way it oversees dairy cows that receive growth hormone or beef cattle that get antibiotics, says FDA spokeswoman Siobhan DeLancey.

By using existing guidelines for so-called animal drugs, the FDA can put those products seeking approval into a process that is already up and running. "They have the staff and the process that allows them to look at this. They do it every day," says Stotish of Aqua Bounty, which has been seeking FDA approval for its fast-growing salmon for years.

Companies must show that their genetic manipulation is safe to the animal and that any food or animal-feed products derived from the animal are safe for the consumer and safe for the environment. Companies must also demonstrate that their claims about the gene-carried traits do occur.