Sedative and antinociceptive effects of romifidine and xylazine in Thoroughbred mares

Abstract

The sedative and antinociceptive effects of romifidine (0.1mg/kg) and of xylazine (1.0mg/kg) on Thoroughbred mares were studied. Sedation was evaluated by quantifying spontaneous locomotor activity (SLA) and head height (HH) in animals placed in automated individual behaviour stalls. Antinociception was determined utilizing a heat irradiation lamp recording the latency time for the hoof withdrawal reflex (HWRL) and the latency time for the skin twitch reflex (STRL) in a randomised block design with 10 replicates. Comparison of the sedative effects of romifidine and of xylazine on SLA showed a faster effect for xylazine. Regarding the sedative effect of the substances based on HH, romifidine caused a longer-lasting effect. Romifidine caused an increase in HWRL and STRL, and xylazine, an agent known for its analgesic effect, did not have an antinociceptive effect based on STRL result. The antinociceptive effect of romifidine was more pronounced than the xylazine effect.