For the detection and assessment of pain in animals both behavioural and physiological measurements are necessary. Cutaneous receptors which responded to noxious stimulation (nociceptors) have been identified in birds and have been characterized physiologically in the chicken. Following cutaneous nociceptive stimulation the chicken showed cardiovascular and characteristic behavioural changes consistent with those seen in mammals and indicative of pain perception. Following major burn trauma (partial beak amputation) there was behavioural and electrophysiological evidence fora pain-free period lasting several hours. This pain-free period was followed by pain-related behaviour with both anatomical and physiological evidence for long-term chronic pain.

While pain has been assessed following nociceptive stimulation and following trauma the painful consequences of chronic disease have not been investigated Spontaneous degenerative joint disease is widespread in certain strains of intensively reared poultry, and while we do not know what effect joint degeneration has on the joint capsule receptors, recent work has shown in the joint capsule of birds there are similar receptor types to those found in mammals and it seems likely that joint degeneration in birds may be accompanied by painful sensations.

Experimental work has clearly detected painful conditions in birds but the alleviation of pain with analgesic drugs is not possible at present because analgesic agents have not been systematically investigated in birds.

Comparing pain in birds with mammals it is clear that, with regard to the anatomical, physiological and behavioural parameters measured, there are no major differences and therefore the ethical considerations normally afforded to mammals should be extended to birds.