Mouse genes may be inserted into pigs to help them process phosphorous more efficiently, or spider genes could be put into goats to make them produce silk in their milk, he said.
Some saw the FDA draft guidelines as a first step as the agency navigates its way through this controversial area of biotechnology.
"Although the FDA's announcement is a good first start, it does not address the risks that GE animals might pose to the environment," said Gregory Jaffe from the Center for Science in the Public Interest.
"Would it be the FDA that would determine whether fast-growing genetically engineered salmon would endanger native salmon populations?" he asked.
Genetic engineering can help ensure that fish grow bigger more quickly, or create animals which produce in their blood or milk substances which can be used to make medicines.
Such techniques, under which a plant or animal's existing DNA is mixed with the DNA of another organism, are already common in agriculture to render crops more resistant to insects or drought.
This is different to cloning in which the scientists create the exact double of an animal or organism.
The FDA and its European counterpart in January approved the sale of meat and diary products coming from cloned animals, judging they posed no risks to humans.
Source-AFP
RAS/SK