Cortisol and pain-related behavior in hot-iron disbudded goat kids sedated with xylazine and locally infiltrated with lidocaine

Abstract

Disbudding induces intense pain-related behavioral and physiological responses in goat kids. Using only regional anesthesia may not be effective in ameliorating these responses. We determined the effect of xylazine-sedation with or without regional infiltration of lidocaine on behavior (tail movements, struggles, vocalizations) and plasma cortisol. Thirty-six goat kids were randomly assigned to six experimental groups (n = 6). The control group (Con) received no treatment at all. The control-disbudded group (ConD) was disbudded without sedative or anesthetic treatment. The control-xylazine (Cxyl) group received 0.05 mg/kg of intravenous xylazine and was not disbudded. Group XylD was administered intravenous xylazine and disbudded 3 minutes later. Group XLD was treated with xylazine as XylD, plus local administration of 1 mL of 2% lidocaine (Pisacaína, PiSA, México) to block the lacrimal and infratrochlear nerves 15 minutes before disbudding. In group Sim, the disbudding procedure was only simulated with no sedative, anesthesia, or disbudding. Disbudding was filmed to analyze behaviors, heart rate (HR) was recorded, and blood samples were taken before and after the procedure to measure cortisol. XylD and ConD kids showed higher cortisol levels than Con and XLD during the first 20 minutes after disbudding (P < 0.05). HR showed a significant increase in ConD kids and a significant decrease in xylazine-treated groups (P < 0.05). More vocalizations were recorded in ConD kids (18.5 ± 4; P < 0.05) and showed no difference compared with XylD animals (13.3 ± 4; P > 0.05). Both XylD and XLD kids displayed a lower total behavioral response than the ConD group (34.3 ± 9.9, 19.6 ± 9.9, and 70.0 ± 9.9, respectively; P < 0.05). In conclusion, thermal disbudding induces physiological and behavioral responses indicative of acute pain. Sedation with xylazine did not control these responses unless combined with a nerve block using local infiltration of 2% lidocaine.