Comparison of neural histomorphology in tail tips from pigs docked using clippers or cautery iron

Abstract

Tail docking of pigs is commonly performed to reduce the incidence of unwanted tail-biting behaviour. Two docking methods are commonly used: blunt trauma cutting (i.e. using side clippers), or cutting and concurrent cauterisation using a hot cautery iron. A potential consequence of tail amputation is the development of neuromas at the docking site. Neuromas have been linked to neuropathic pain, which can influence the longer-term welfare of affected individuals. To determine whether method of tail docking influences the extent of neuroma formation, 75 pigs were allocated to one of three treatments at birth: tail docked using clippers; tail docked using cautery iron; tail left intact. Tail docking was performed at 2 days of age and pigs were kept under conventional conditions until slaughter at 21 weeks of age. Tails were removed following slaughter and subjected to histological examination. Nerve histomorphology was scored according to the following scale: 1=discrete well-organised nerve bundles; 2=moderate neural proliferation and disorganisation affecting more than half of the circumference of the tail; 3=marked neural proliferation to form almost continuous disorganised bundles or non-continuous enlarged bundles compressing the surrounding connective tissue. Scores of 2 or 3 indicated neuroma formation. Scores were higher in docked pigs than undocked pigs (P<0.001), but did not differ between pigs docked using clippers and those docked using cautery (P=0.23). The results indicate that tail docking using either clippers or cautery results in neuroma formation, thus having the potential to affect long-term pig welfare.

Transcriptomics Analysis of Porcine Caudal Dorsal Root Ganglia in Tail Amputated Pigs Shows Long-Term Effects on Many Pain-Associated Genes

“…However, even tail docking is not a total safeguard against the loss of a portion of the tail under conditions of severe tail biting, which means that pigs can experience traumatic tail “amputation” through a portion of the tail being bitten off later in life (2). Concerns exist about the effects of tail amputation injury with respect to the initiation of short (acute) and long-term (chronic) pain in the tail stump (3–8). Tail amputation injury typically involves the severing of the caudal nerves in the tail which lead to the formation of “traumatic” or “amputation” neuromas in the tail stump (9).…”

Mechanical/thermal sensitivity and superficial temperature in the stump of long-term tail-docked dairy cows

“… Petrie et al (1996) indicate that tail docking would induce tissue damage that leads to neuromata development and concurrent neuropathic pain. Moreover, neuroma development has been previously reported in tail-docked lambs ( French & Morgan, 1992 ; Fischer & Gregory, 2007 ), pigs ( Herskin, Thodberg & Jensen, 2015 ; Kells et al, 2017 ) and dogs ( Gross & Carr, 1990 ). Peripheral neuromas occur in 10–25% of human amputees, and are generally formed after injury or surgical procedures, resulting in neuropathic pain, residual limb pain, functional impairment and psychological distress ( Rajput, Reddy & Shankar, 2012 ), increasing sensitivity to mechanical and thermal stimulation ( Toia et al, 2015 ; O’Reilly et al, 2016 ; Yao et al, 2017 ).…”

Mechanical/thermal sensitivity and superficial temperature in the stump of long-term tail-docked dairy cows

“…Petrie et al (1996) indicate that tail docking would induce tissue damage that leads to neuromata development and concurrent neuropathic pain. Moreover, neuroma development has been previously reported in tail-docked lambs (French & Morgan 1992;Fisher & Gregory 2007), pigs (Herskin, Thodberg & Jensen 2015;Kells et al 2017) and dogs (Gross & Carr 1990). Peripheral neuromas occur in 10-25% of human amputees, and are generally formed after injury or surgical procedures, resulting in neuropathic pain, residual limb pain, functional impairment and psychological distress (Rajput, Reddy & Shankar 2012), increasing sensitivity to mechanical and thermal stimulation (Toia et al 2015;O´Reilly et al 2016;Yao et al 2017).…”