Objective: This study assessed the use of a topical anesthetic as a feasible approach to reduce pain during piglet castration using a minimal anesthesia protocol.
Animals: 18 male piglets, aged 3-6 days, were included in this study.
Methods: A minimal anesthetic state was induced with isoflurane administered by facemask, with anesthetic depth individually adjusted based on responses to interdigital pinch. To desensitize the scrotal skin, a vapocoolant was applied 3 times. Scrotal incisions were made subsequently and Tri-Solfen (TS) or Placebo (P) was administered in both incisional gaps. After 30 seconds, the spermatic cords were severed followed by a further application of TS/P to both incision edges. Nociception-related variables, such as mean arterial blood pressure (MAP), heart rate (HR), and nocifensive movements, were assessed.
Results: Significant differences in MAP changes were assessed between the TS (14 ± 4 mmHg) and the P group (36 ± 8 mmHg) for cutting the spermatic cords. Furthermore, significantly fewer nocifensive movement score points appeared in the TS than in the P group (0; IQR = 0 vs 5; IQR = 6).
Clinical relevance: In this anesthesia model, the application of TS after skin incision significantly reduced MAP responses and nocifensive movements with spermatic cord transection compared with the application of P. However, the waiting period between TS-application and spermatic cord transection might limit the benefit of the method in conscious piglets, as pain during castration is reduced but additional stress is caused by the prolonged handling. Furthermore, using a vapocoolant did not provide anesthesia for skin incisions.