Effect of sedatives on rumen motility in sheep

Abstract

Abstract Rumen motility is depressed by a number of anesthetic agents, making them unsuitable for the reduction of animal anxiety and distress during experimental investigations of rumen motility. Little is known about the influence on rumen motility of chemical agents that induce sedation without unconsciousness. A pilot trial was performed to assess the effect of three commonly used ruminant sedatives on rumen motility. Xylazine, acetylpromazine and diazepam were individually administered by intravenous injection to 3 adult sheep ewes. Animal behaviour was observed and ultrasound monitoring was used to assess rumen contractions in the animals over a range of sedative doses. At low dosages 0.05 mg/kg, xylazine reduced contraction frequency after 5 min, and at higher dosages 0.125 mg/kg full atony was observed. In contrast, neither acetylpromazine (0.02–0.1 mg/kg) and diazepam (0.2–0.5 mg/kg) depressed rumen motility. Diazepam was also observed to give greater sedative influence than acetylpromazine, both in terms of muscular and cognitive sedation. Sedative effects lasted approximately 20–30 min after administration, after which the effects diminished rapidly. We conclude that diazepam at dosages of 0.3–0.5 mg/kg is suitable for procedures requiring short term sedation of sheep while preserving rumen motility.