Ultrasonographic evaluation of reticular motility in cows after administration of atropine, scopolamine and xylazine.

The goal of this study was to evaluate the effect of various dosages and routes of administration of atropine, scopolamine and xylazine on reticular motility in cows. Groups of five cows received atropine, scopolamine or xylazine at dosages varying from 0.01 to 0.20 mg/kg. The drugs were administered intramuscularly and intravenously; atropine was also given subcutaneously. A total of 17 trials, each using five cows, were carried out. Reticular motility was assessed for 3 min immediately prior to the administration of a drug and for 21 min after administration, and the latter period was divided into seven 3-min intervals. The motility was further assessed during 3-min periods every 10 min starting 28 min and ending 141 min after administration of a drug. During each 3-min interval, the number of reticular contractions or the occurrence of reticular atony was determined. Onset and duration of reticular atony were assessed. All three drugs inhibited reticular motility but onset varied with route of administration and dosage. As expected, the onset of reticular atony occurred most rapidly after intravenous administration of each drug, followed by intramuscular and subcutaneous administration. Reticular atony occurred 0-3.0 min after the intravenous administration of each drug and at all dosages except the lowest dosage of atropine. Atony lasted for 3-111 min. Reticular atony occurred 3-18 min and 9-15 min after intramuscular and subcutaneous administration, respectively. It lasted 32-108 min and 39-122 min for the intramuscular and subcutaneous routes, respectively. For each drug, higher dosages resulted in a more rapid onset and longer duration of reticular atony than did lower dosages. This study demonstrated that administration of atropine, scopolamine and xylazine results in reticular atony. Whether this has clinical relevance requires further investigation.