Decreased sedation by xylazine and high blood pressure in cows with BSE.

Fifteen cows with bovine spongiform encephalopathy (BSE) and 90 healthy cows were given xylazine intramuscularly at a dosage of 0.15 mg/kg bodyweight. The onset of sedation and of drooling was recorded, and the heart and respiratory rates and the systolic and diastolic blood pressure were measured every five minutes for 40 minutes. All the healthy cows but only five of the 15 cows with BSE became sedated, and the period between the administration of xylazine and the onset of sedation was twice as long in the cows with BSE than in the healthy cows (15.0 7.5] and 7.6 2.6] minutes). Throughout the observation period, the blood pressure of the cows with BSE was significantly higher than that of the healthy cows, and the blood pressure of the healthy cows, but not of the cows with BSE, decreased significantly towards the end of the observation period.