From Dr. Ian J.H. Duncan, Professor of Poultry Science
University of Guelph, Ontario
"There is now good morphological, neurophysiological and behavioral evidence that beak trimming leads to both acute and chronic pain. The morphological evidence is that the tip of the beak is richly innervated and has nociceptors or pain receptors. This means that cutting and heating the beak will lead to acute pain. In addition, it has been shown that as the nerve fibers in the amputated stump of the beak start to regenerate into the damaged tissue, neuromas [tumors] form. Neuromas are tiny tangled nerve masses that have been implicated in phantom limb pain (a type of chronic pain) in human beings.
"The neurophysiological evidence is that there are abnormal afferent nerve discharges in fibers running from the amputated stump for many weeks after beak trimming-long after the healing process has occurred. This is similar to what happens in human amputees who suffer from phantom limg pain.
"The behavioral evidence is that the behavior of beak-trimmed birds is radically altered for many weeks compared to that which occurs immediately before the operation and compared to that shown by sham-operated control birds. In particular, classes of behavior involving the beak, namely feeding, drinking, preening and pecking at the environment, occur much less frequently, and two behavior patterns, standing idle and dozging, occur much more frequently, The only reasonable explanation of these changes is that the birds are suffering from chronic pain."
Duncan, "The Science of Animal Well-Being," rpt. from a speech in Animal Welfare Information Center Newsletter (National Agricultural Library) 4.1 (Jan.- March 1993): 5.