We aimed to examine the effect of hot-iron disbudding on serum thiol-disulphide homeostasis levels as a marker of oxidant stress in relationship with trauma in calves under sedation, local anaesthesia, and the non-steroidal anti-inflammatory drug ketoprofen. A total of 30 Holstein calves were enrolled in the study and allocated into three groups: disbudded following sedation with xylazine (n=10) (group I); disbudded following sedation (xylazine) and local anaesthesia with lidocaine (n=10) (group II); and disbudded after sedation (xylazine), local anaesthesia (lidocaine), and ketoprofen (n=10) (group III). Blood samples were withdrawn before (0. min) and 30, 60, 90, and 120 min after dehorning. Serum native thiols, total thiols, and disulphide levels were detected with a novel assay. Native thiol and total thiol levels were reduced in all groups without any significance during the study period. At the 90th min of the study, native thiol levels in group II were significantly lower than in groups I and III. There were no significant alterations in total thiol levels in both groups. Disulphide levels showed no significant changes in group, time, and group by time interactions, but at the 60th min, groups I and III had the lowest levels. Disulphite/ native thiol, disulphite/total thiol, and native thiol/total thiol levels had significant group alterations in the 60th min. The reduction of native thiol and total thiol levels in all groups without significance might be related to the antioxidant activity of plasma; however, it is thought that the pain management procedures should be related to the sensitive oxidative balance by thiols.