Preliminary results of the efficacy of an alternative pain management approach for piglet castration.

Surgical castration of piglets without anaesthesia or analgesia is a painful and stressful procedure. Pharmacological treatments to reduce pain can present some limitations as shown by several studies performed on human neonates, due to possible adverse and discordant effects. Alternative non-pharmacological approaches seem to be effective and feasible. For instance, in human neonates, small amounts of sweet solutions were proven to be effective, presumably mediated by endogenous opioids. The aim of this study was to evaluate the efficacy of an alternative pain management approach (oral glucose) on behavioural and physiological responses of piglets subjected to surgical castration. Sixteen three-day-old male piglets were recruited from 4 different litters and allocated to 4 treatment groups: CG – surgical castration and oral administration of glucose 10%; CW – surgical castration and oral administration of water; MG – manipulation without castration and oral administration of glucose 10%; MW – manipulation without castration and oral administration of water. Surgical castration was carried out by a trained operator, in compliance with the Council Directive 2008/120/EC. Piglets of the same litter were isolated into a small nursery and filmed for 15 min before and 30 min after castration. Ninety-six pictures of the faces were collected pre- and post-procedure and scored with the Piglet Grimace Scale (PGS) by 3 treatment-blind observers. Heart rate before and during the procedure and latency at the first suckling were recorded. The inter-observer reliability was good with an overall interclass correlation coefficient value of 0.77. In the CW group, mean PGS score before castration was 1.89 ± 1.96 and increased to 3.11 ± 1.62, after castration. During the procedure, mean heart rate was lower in castrated piglets receiving glucose 10% (127 bpm) compared to ones receiving water (220 bpm). Piglets receiving water required a longer time (s) to suckle (CG =36.0; CW =121.0; MG =10.3; MW =28.3). Although preliminary, these results suggest that an alternative non-pharmacological approach might represent an effective method to control pain induced by routine husbandry procedures in pigs. Further research providing oral glucose in combination with pharmacological treatment is required to identify the most feasible and effective pain relief treatment for on-farm surgical castration in pigs.