Effect of rectal or intravenous tramadol on the incidence of pain-related behaviour after disbudding calves with caustic paste

To evaluate the efficacy of tramadol (suppositories or intravenous) in alleviating pain after caustic paste disbudding, two behaviour-assessing methods were used during the first hour post-disbudding: the objective recording of four pain-related behaviours and the subjective scoring pain on a scale of 0–10 (Numerical Rating Scale, NRS). Sixty dairy calves were allocated to five groups: disbudded with no treatment (C); disbudded after rectal tramadol (TR-r); disbudded after i.v. tramadol (TR-iv); sham-disbudded after i.v. tramadol (TR-SD); sham-disbudded with no treatment (SD). All disbudded groups showed more head shakes, head rubs and transitions for the first 15 min when compared with sham-disbudded calves. Animals treated with rectal tramadol showed more head shakes, head rubs and transitions than all other groups from 15 to 30 min after disbudding. Ear flicks were more frequent in disbudded calves than in sham-disbudded ones at the end of the observation period (45–60 min). NRS showed a higher score at all moments for all disbudded groups when compared with sham-disbudded. Sham-disbudded animals with i.v. tramadol had a higher score than sham-disbudded with no treatment at the first observation period (15 min). We concluded that caustic paste disbudding causes severe pain for the first 30 min after applying the paste and that tramadol is not efficient in controlling this pain but when given i.v. it may help in reducing post-operative nociception. We also showed that tramadol can be used safely in young calves although after i.v. administration it may cause some sham-disbudded animals to shake their heads and ears during the first minutes after injection. NRS showed to be a reliable method of evaluating the acute pain in caustic paste disbudded calves.