Oral lesions in the chicken: behavioural responses following nociceptive stimulation

The behaviour of normal birds and birds with ulcerated buccal lesions was described following oral stimulation with Acetylcholine chloride (ACh) and Bradykinin (BK). Both groups of birds showed normal oral behaviour but a number of birds with oral lesions showed a behaviour pattern which had been previously seen in our laboratory following nociceptive stimulation. The birds remained motionless in a crouch-like stance with the head pulled into the body and a significantly reduced number of alert head movements. The onset and duration of this immobility response was compared with reports of pain in humans in the blister-base test using similar concentrations of ACh and BK. It was concluded that nocifensive responses of the chicken fulfil many of the requirements for the definition of pain in animals.