Topical wound anaesthesia: efficacy to mitigate piglet castration pain

Abstract

Objective There is a critical need for safe and effective analgesic treatments to address pain resulting from surgical husbandry procedures in livestock. Piglet castration results in acute pain and stress to the animal; however, it is performed globally on millions of piglets annually, often without any analgesia what‐so‐ever. Tri‐Solfen® (Animal Ethics Pty Ltd, Yarra Glen, Victoria, Australia) is a combination local anaesthetic and antiseptic formulation which, applied topically to wounds, has proven effective, and is registered for use to alleviate pain associated with castration (and other wounds) in lambs and calves in Australia and New Zealand. It is also reported to be effective to reduce pain in piglets following castration. Design This randomised, blinded, placebo‐controlled study examined the safety and efficacy of the formulation, administered via an adapted wound instillation method, to control pain both during and following piglet castration. Method Piglets received Tri‐Solfen or placebo, instilled to the wound immediately following skin incision. A 30 s wait period was then observed prior to completing castration. Pain mitigation was assessed by grading nociceptive resistance movements and piglet vocal response during castration, as well as by grading response to mechanical sensory stimulation of the wound (von Frey and needlestick) following castration. Results There was a significant reduction in nociceptive motor and vocal response during castration and in response to mechanical sensory wound stimulation up to and including 2 h following castration. There were no adverse events. Conclusion Administered via this method, Tri‐Solfen is effective to mitigate acute peri‐operative castration pain in piglets.

Local Anesthesia in Piglets Undergoing Castration—A Comparative Study to Investigate the Analgesic Effects of Four Local Anesthetics Based on Defensive Behavior and Side Effects

“…As physiological parametersi.e., blood parameters, such as cortisol [ 12 , 16 , 17 , 18 , 19 , 20 ] adrenalin and adrenocorticotropic hormones [ 16 , 18 , 19 ] and changes in heart rate and blood pressure [ 21 ] can be assessed. Furthermore, behavioral variables, such as defensive movements [ 10 , 21 , 22 ] and vocalization [ 8 , 20 , 23 , 24 , 25 , 26 , 27 ] can be used for pain assessment. Additionally, Bilsborrow et al [ 28 ] described an objective test to assess pain in piglets where the navigation time through a handling chute is determined.…”

Optimal Methods of Documenting Analgesic Efficacy in Neonatal Piglets Undergoing Castration

“…Neural markers of pain mitigation, such as the expression of the c-fos gene and its protein product, Fos, in neurons of the spinal cord [75], are significantly reduced when piglets are castrated under effective local or general anaesthesia, as compared with piglets castrated without anaesthesia [43]. Furthermore, this is associated with a dramatic reduction in the nociceptive motor and vocal response to castration [31,32,74]. Additionally, reduced postoperative hyperalgesia has been documented in local anaesthetic-treated piglets [31,32].…”

“…Furthermore, this is associated with a dramatic reduction in the nociceptive motor and vocal response to castration [31,32,74]. Additionally, reduced postoperative hyperalgesia has been documented in local anaesthetic-treated piglets [31,32]. Together, these factors are considered to indicate that biomarkers of activation of the HPA axis, and inflammatory response lack specificity for pain mitigating effects of local and general anaesthetics, and are poor indicators of pain in piglets castrated under general or local anaesthesia [1].…”

“…This has proven effective to alleviate castration pain in lambs and calves and is now widely used on farms in Australia [29,30]. Administered immediately following skin incision, the topical anesthetic formulation (containing 5% lidocaine, 0.5% bupivacaine, cetrimide and 1:2000 adrenalin), can act rapidly, within 30 seconds, to anaesthetise the wound and the exposed cordal tissues prior to severing the spermatic cords [31], which is considered the most painful part of the procedure. The longer acting local anaesthetic (bupivacaine), is included in the formulation, to assist provide extended post-operative sensory analgesia [32].…”

“…On this basis, a range of outcome variables have been used to assess piglet pain during and following castration, and to assess amelioration of pain due to use of local anaesthetics or analgesia. These include; (a) physiological responses during the procedure [22,24,27,28,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][64][65][66][67][68][74][75][76][77][78], (b) nociceptive motor responses during the procedure [27,28,31,47,49,50,64,74]; (c) vocal responses during the procedure [22,[24][25][26][27][28]31,46,[50][51]…”