Non-sequitur. The existence of transgenic animals only proves that ID is possible, not that it is responsible for the existence of all life. The claim is akin to asserting that the existence of Ford automobiles is proof that all automobiles were made by Ford.
Yes, the existence of transgenic animals proves that ID is possible...and the existence of transgenic animals is also unexplained by the Theory of Evolution.
Ergo, the Theory of Evolution can not explain the origins of all life.