Animals are different from humans, so if you can manipulate the animals you are experimenting with so that they better represent humans you are more likely to get useful results. But there must be limits on the degree to which animals are altered. They must be respected, not distorted in some hideous fashion.

GM techniques are right at the cutting edge and scientists are very excited about them, which makes them hard to resist. I agree science must progress and tackle disease, but we must also take into account the suffering of animals. We all want cures for diseases such as cystic fibrosis and Parkinson's, but we must maintain morality and decency in pursuit of solutions.

Of course the tiny overall drop in experiment numbers is good news and lots of the scientists involved are decent people doing a good job, but if more attention were paid to the proper design of experiments and better statistical procedures in place to evaluate results, this number could be brought down more significantly.

Also, mice and rats that are modified for use as models for human diseases often turn out to be much less useful than anticipated. A mouse with cystic fibrosis, for example, doesn't always fit precisely the experiment for which it has been developed. There is a lot of waste.

The most likely way to produce accurate results is to conduct tests with humans instead. Techniques are emerging with tests that can ethically be done on humans with the actual disease. There are limits but it's an advancing frontier. The more clinical research on actual patients, providing its done with strict ethical controls, the more likely are relevant results.

The other way to limit animal experimentation is to be critical about the way the development of modified animals is going before you start producing them in large numbers.

Testing on GM animals isn't intrinsically worse than testing on normal animals, but when you breed animals to develop diseases very early on in their lives, some of the outcomes can be extraordinarily harsh. All the time the issue scientists must consider is the balance of potential human benefit, weighed against the suffering and the dignity of the subjects being tested.