Long-term hyperalgesia and traumatic neuroma formation in tail-docked lambs

Abstract

This study aimed to determine if tail-docking induces long-term hyperalgesia, chronic pain and histopathological changes in tail stumps of tail-docked lambs. Fifty male lambs of 45 days of age were randomly allocated in two groups. One group of 25 lambs was tail-docked using a hot cautery iron and a second group of 25 lambs was subjected only to handling as a control group (undocked lambs). Prior to tail-docking and at intervals of 15, 30, 60 and 90 days after the procedure, infra-red thermography (IT) and mechanical nociceptive thresholds (MNTs) tests were carried out in both lambs' tails/stumps, and animals were weighed. In addition, the visual degree of inflammation of tail stumps was evaluated. Finally, animals were slaughtered in a commercial slaughterhouse and tail sections of ten lambs from each group were examined histopathologically. Tail-docking was associated with an inflammatory process according to IT and visual observation in tail stumps at 15 and 30 days post-docking. Tail-docked lambs had lower MNTs than undocked lambs at all evaluated times after tail-docking, indicating the presence of long-term hyperalgesia. Also, traumatic neuroma formation was found in tail stumps of 2/10 tail-docked lambs, and 6/10 presented neuromatous tissue development. It is concluded that tail-docking induces acute and chronic pain in lambs, initially through inflammation, and then via long-term hyperalgesia and traumatic neuroma formation. These long-term findings would have negative implications for the animal welfare of tail-docked lambs.

Animal welfare in Latin America: Trends and characteristics of scientific publications

“…Animal suffering due to common husbandry practices during the on-farm stage of production like tail docking, dehorning and castration in various species has been an issue of debate among farmers, practitioners and the public in general. It was interesting to find several surveys in Latin America dealing with the perception of pain in animals by farmers and veterinary professionals, as well as studies on the effects of these husbandry practices directly on the expression of pain and stress in the animals (82)(83)(84)(85)(86)(87)(88). On the other hand, the tendency of people to increasingly consume more organic products and those produced under welfare friendly systems that avoid animal suffering as much as possible is growing (3,20,89).…”

Analgesia for Sheep in Commercial Production: Where to Next?

“…The acute pain of tail docking of lambs was identified using IRT and nociception assessment (indicators of inflammation), while histology was used to assess the chronic aspects of pain by assessing traumatic neuroma formation [ 93 ]. Using histology to inform on pain states is insightful as it provides a measure of the impacts of procedures on the more chronic aspects of pain.…”

The Neuroimmune Interface and Chronic Pain Through the Lens of Production Animals

“…Commonly, this practice is performed in young animals without anesthesia or analgesia due to financial and practical implications as well as the absence of evidence showing significantly improved production outcomes when analgesia is used ( Sutherland and Tucker, 2011 ). Tail docking is acutely painful ( Molony et al, 1993 ; Lomax et al, 2010 ; Sutherland and Tucker, 2011 ; Herskin and Di Giminiani, 2018 ) and there is growing evidence of chronic pain associated with the procedure ( Kent et al, 1999 ; Di Giminiani et al, 2017b ; Troncoso et al, 2018 ; Larrondo et al, 2019 ).…”

“…Neuromas are benign proliferations of epineural, perineurial, and endoneurial connective tissue and axons that can form at the end of severed nerves and have been associated with chronic neuropathic pain and conditions such as phantom limb pain ( Flor et al, 2006 ). Neuroma formation following tail docking in livestock has been documented in sheep ( French and Morgan, 1992 ; Larrondo et al, 2019 ), pigs ( Sandercock et al, 2016 ; Kells et al, 2017 ), and in dairy cows ( Eicher et al, 2006 ; Troncoso et al, 2018 ). Castration site neuromas have also been identified in horses and may be related to chronic hind limb lameness and back pain ( Bengtsdotter et al, 2019 ).…”

“…Research into the long-lasting effects of painful husbandry procedures in livestock is limited ( Viñuela-Fernández et al, 2007 ; Herzberg et al, 2020b ; Small et al, 2021 ). However, growing interest in improving the welfare of animals is driving further investigation of the long-term consequences of various husbandry practices and chronic disease in livestock ( Troncoso et al, 2018 ; Larrondo et al, 2019 ; Sandercock et al, 2019 ; Herzberg et al, 2020a ).…”