Assessment of tail sensitivity to mechanical stimulation before and shortly after tail resection in juvenile pigs
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Tail biting is a behavioural abnormality in pigs leading to possible tail injury and amputation. It induces the development of traumatic neuromas in the stump and is related to behavioural changes indicative of pain. Presently, it is not known whether such tail trauma is associated with acute or sustained peripheral or spinal changes contributing to lasting tail sensitization. In humans, limb amputation can lead to abnormal neural activity and decreased nociceptive thresholds. Tail resection was performed as a model of tail biting to assess the short-term consequences on tail sensitivity to mechanical stimulation. Female pigs were assigned to three treatments (‘Intact’: sham-resection; ‘Major resection’: 2/3 of tail removed; ‘Minor resection’: 1/3 of tail removed; n=16 per treatment), with surgical amputation at 17-18 weeks of age. Mechanical sensitivity thresholds (tail flick or tail clamp withdrawal responses) were assessed along the length of the tail using a Pressure Application Measurement device. Three stimuli were delivered to 3 distinct regions of the tail (1) proximal to the body; (2) intermediate; (3) distal to the body. Measurements were obtained in a single session, 3 days pre-surgery and one week after tail resection. Baseline sensitivity thresholds were significantly different (P<0.01; one -way repeated measures ANOVA) across the 3 tail regions, with region 1 responding at significantly higher thresholds than the two more distal regions (region 1: 650 gf (448-844); region 2: 531 gf (442-710); region 3: 543 gf (407-703). Tail resection did not induce a significant change in mechanical sensitivity thresholds one week post-surgery. Clear withdrawal responses to mechanical stimulation were observed and allowed characterisation of sensitivity thresholds in the pig tail. The lack of an effect of the acute tissue trauma on tail sensitivity thresholds requires further investigation. Future work will examine the levels of sensitivity in relation to known stages of neuroma formation.
Other Titles/Title of Conference
International Society for Applied Ethology UK & Ireland Regional Meeting, Cork, Republic of Ireland