This study aims to evaluate the rumen motility before and after a continuous infusion of different rates of propofol with or without an association to fentanyl in Holstein calves fed with corn silage and commercial concentrated ration. Eight animals, averaging 9 months old and weighing 100-180 kilograms, will be used and all of them will be subjected to two treatments with a one week interval between. Selected randomly, four animals will be part of propofol (GP) and fentanyl group (GF), in this order ; the rest will be assigned to the reverse order of the groups. In the first group (GP), the animals will be induced to anesthesia with propofol 5mg/kg intravenously (IV). The fentanyl group (GF) will be induced with propofol at a dose of 3mg/kg associated to a 0,001mg/kg fentanyl IV dose and, just like GP, will be intubated with compatible size tracheal probes and positioned in right lateral decubitus, breathing ambient air spontaneously. Anesthetic maintenance will be performed by continuous infusion of propofol at a rate of 0,6mg/kg/min IV, with or without a 0,001mg/kg/hour fentanyl dose. In both groups, the drugs will be administered by an infusion pump during 60 minutes. Hemodynamic variables such as heart rate (FC); systolic, diastolic and mean blood pressure (PAS, PAD, and PAM, respectively); respiratory frequency (f ); and also the rumen auscultation, will be measured before anesthesia (MB), and 15, 30, 45 and 60 minutes after its start (M15, M30, M45 and M60 respectively). The rumen auscultation will also be held before and after the fasting period.
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