Denise Caruso, author of Intervention: Confronting the Real Risks of Genetic Engineering and Life on a Biotech Planet, has an excellent op-ed that explains the deep concerns about animal cloning. If you have doubts about this issue, or want to be better informed, this piece is a good place to start.
She makes the point that the FDA has not assessed the real risks of these animals — not enough is known about them. More importantly, the subject of the FDA risk assessment was extremely limited.
In the case of cloned meat and milk, for example, the FDA focused on nutritional and compositional equivalence, which means that according to its tests, the chemicals that make up the food appear to be “substantially equivalent” to those in traditional food. In the ordinary practice of science, this kind of intensely narrowed focus isn’t a failing. Experiments have to be rigidly controlled so they consistently produce or cause the same result, over and over again.
But the results of these rigidly controlled experiments often lose their evidentiary power once a living biotech product is released into the real, uncontrolled circumstances of life outside the laboratory, where they grow and reproduce and where someone has to decide whether they’re safe.
This is just a snippet, but in total, it’s about the best piece I’ve seen questioning the safety of these animals.