Evaluation of analgesia efficacy in piglets undergoing surgical castration and tail docking
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Abstract
Surgical castration and tail docking are performed routinely on commercial pig farms to minimize boar taint, aggression and tail biting among pigs. While these procedures are known to be painful, piglets are not always provided sufficient analgesia or anesthesia for pain relief. This thesis project aimed to determine which analgesic drug or drug combination sufficiently reduced surgical castration and tail docking pain in piglets using behavior, vocalization and facial grimace analysis. It also assessed whether topical anesthesia could be used as an adjunct to mitigate pain and whether male and female piglets respond differently to pain or pain treatments. Finally, it sought to validate the Piglet Grimace Scale (PGS) as a tool for pain assessment. Two nonsteroidal anti-inflammatory drugs, meloxicam (0.4 mg/kg or 1.0 mg/kg) or ketoprofen (6.0 mg/kg), administered intramuscularly (IM) 20 min prior to surgical castration were ineffective at reducing pain behaviors and facial grimacing of piglets up to 24 h post-procedure. Meloxicam (0.4 mg/kg) was also insufficient at alleviating behavioral indicators of tail docking pain. Buprenorphine (an opioid, 0.04mg/kg IM) significantly reduced piglet pain behaviors and facial grimacing post-castration and tail docking with no obvious side effects. A multimodal approach to pain management [0.4 mg/kg meloxicam, 0.04 mg/kg buprenorphine, and topical lidocaine (Maxilene®)] did not provide piglets with significantly more pain relief than administration of buprenorphine alone. At the time of castration and tail docking, none of the drug treatments were able to reduce pain-related vocalizations. There was no difference in pain behavior or response to analgesia treatments between male and female piglets. The PGS corresponds well to piglet pain behaviors when experienced scorers are used, and this may become a useful tool for piglet pain assessment. These findings are important for improving piglet welfare in the swine industry and may be used to inform future recommendations concerned with piglet pain control.