In Douglas Adams's novel The Restaurant At The End Of The Universe, the character Arthur Dent is horrified when a cow-like creature is wheeled to the restaurant table, introduces itself as the dish of the day and proceeds to describe the cuts of meat that are available from its body. The cow has been bred to want to be eaten, and to be capable of saying so.

As so often happens with Adams's work, the truth isn't too far behind. This week we report on proposals to genetically engineer livestock to be untroubled by pain - something all too common in intensively farmed animals (see Pain-free animals could take suffering out of farming). The concept treats cows, pigs and chickens as if they were inanimate objects whose suffering is like a computer program in need of debugging.

As with Adams's fictional cow, there is something deeply unsettling about an animal engineered to be pain-free. One researcher called the idea "icky", and conversations about it around our office often ended in awkward silence, the thought too unsavoury to discuss.

But also as with Adams's cow, there is a cold logic that is hard to argue against. Eating an animal that wants to be eaten is surely better than eating one that doesn't; engineering a farm animal so it does not suffer from pain is surely more humane. If factory farming must exist, then surely we have a moral duty to limit the distress it inflicts.

This doesn't mean we should welcome the creation of pain-free animals, though. The reason we find the idea so disquieting is that it runs counter to our visceral sense of right and wrong. This is known as the "yuck factor" and it is a common reaction to advances in biotechnology and biomedicine such as cloning, genetic modification and human-animal chimeras.

Some conservative commentators argue that the yuck factor is a reliable indicator that a moral Rubicon has been crossed. Yet all too often such distaste is irrational and a barrier to progress. Progressive thought often comes from ignoring such reactions and thinking things through logically instead.

In this case, however, there is value in the yuck factor. Yes, logically speaking, pain-free animals make sense. But only in a world that has already devalued animal lives to the point where factory farming is acceptable. Our visceral reaction to pain-free animals is actually a displaced reaction against the system that makes them necessary.

Too many of us are too attached to the pleasures of affordable meat to consider the plight of factory-farmed animals. If the proposal to create pain-free animals achieves anything, it is to force us to confront the pain and suffering that our diets inflict. End factory farming, and the "problem" of pain-free animals goes away too.