Opinion - NY Times
Op-Ed Contributor
Not Grass-Fed, but at Least Pain-Free

By ADAM SHRIVER
Published: February 18, 2010
St. Louis

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 farms.

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.