Opinion - NY Times
Not Grass-Fed, but at Least Pain-Free
By ADAM SHRIVER
Published: February 18, 2010
IN the 35 years since Peter Singer’s book “Animal Liberation” was published,
jump-starting the animal rights movement in the United States, the number of
animals used in cosmetics testing and scientific research has dropped
significantly, and the number of dogs and cats killed in shelters has fallen by
more than half. Nevertheless, because the amount of red meat that Americans eat
per capita has held steady at more than 100 pounds a year as the population has
increased, more animals than ever suffer from injuries and stress on factory
Veal calves and gestating sows are so confined as to suffer painful bone and
joint problems. The unnatural high-grain diets provided in feedlots cause severe
gastric distress in many animals. And faulty or improperly used stun guns cause
the painful deaths of thousands of cows and pigs a year.
We are most likely stuck with factory farms, given that they produce most of the
beef and pork Americans consume. But it is still possible to reduce the animals’
discomfort — through neuroscience. Recent advances suggest it may soon be
possible to genetically engineer livestock so that they suffer much less.
This prospect stems from a new understanding of how mammals sense pain. The
brain, it turns out, has two separate pathways for perceiving pain: a sensory
pathway that registers its location, quality (sharp, dull or burning, for
example) and intensity, and a so-called affective pathway that senses the pain’s
unpleasantness. This second pathway appears to be associated with activation of
the brain’s anterior cingulate cortex, because people who have suffered damage
to this part of the brain still feel pain but no longer find it unpleasant. (The
same is true of people who are given morphine, because there are more receptors
for opiates in the affective pain pathway than in the sensory pain pathway.)
Neuroscientists have found that by damaging a laboratory rat’s anterior
cingulate cortex, or by injecting the rat with morphine, they can likewise block
its affective perception of pain. The rat reacts to a heated cage floor by
withdrawing its paws, but it doesn’t bother avoiding the places in its cage
where it has learned the floor is likely to be heated up.
Recently, scientists have learned to genetically engineer animals so that they
lack certain proteins that are important to the operation of the anterior
cingulate cortex. Prof. Min Zhuo and his colleagues at the University of
Toronto, for example, have bred mice lacking enzymes that operate in affective
pain pathways. When these mice encounter a painful stimulus, they withdraw their
paws normally, but they do not become hypersensitive to a subsequent painful
stimulus, as ordinary mice do.
Prof. Zhou-Feng Chen and his colleagues here at Washington University have
engineered mice so that they lack the gene for a peptide associated with the
anterior cingulate gyrus. Like the animals given brain lesions, these mice are
normally sensitive to heat and mechanical pain, but they do not avoid situations
where they experience such pain.
Given the similarity among all mammals’ neural systems, it is likely that
scientists could genetically engineer pigs and cows in the same way. Because the
sensory dimension of the animals’ pain would be preserved, they would still be
able to recognize and avoid, when possible, situations where they might be
bruised or otherwise injured.
The people who consumed meat from such genetically engineered livestock would
also be safe. Knockout animals have specific proteins removed, rather than new
ones inserted, so there’s no reason to think that their meat would pose more
health risks for humans than ordinary meat does.
If we cannot avoid factory farms altogether, the least we can do is eliminate
the unpleasantness of pain in the animals that must live and die on them. It
would be far better than doing nothing at all.
Adam Shriver is a doctoral student in the philosophy-neuroscience-psychology
program at Washington University.