Physiological and Behavioural Responses in Piglets Submitted to Castration: Preliminary Study

With the perspective to test drugs that may reduce pain due to surgical castration, this preliminary study tries to find out a robust and valid method for pain assessment in piglets. In the present study three treatments were applied: handling (H), tail docking (TD) and surgical castration + tail docking (CTD). To evaluate pain response to the treatments different variables were analyzed: movement latency (time from placing back the piglet inside the farrowing crate after treatments and its first movement towards the nest or the sow), rectal temperature and plasma cortisol and lactate levels. Movement latency was measured for all treatments. Rectal temperature was measured before treatments H and CTD, and 1, 3, 5, 24 hours later. Blood samples for cortisol and lactate determination were collected 1 hour before treatments H and CTD, right after and 3, 5, 24 hours later. The significant increase of movement latency for CTD compared to H showed that pain can be assessed by this type of measure. Rectal temperature was significantly affected by time (P < 0.01) but not by treatment likely due to several factors that might have confounded the studied effect. Cortisol was significantly affected by interaction time*treatment (P < 0.01) particularly due to the high peak for CTD right after the surgical procedure. Lactate was modified only by time (P < 0.01). This preliminary study suggests that a non invasive and easy measure such as movement latency is a promising method to assess pain in piglets after surgical castration and tail docking