Chemical immobilisation of lions: weighing up drug effectiveness versus clinical effects.

Selection of an effective drug combination to immobilise African lions (Panthera leo) requires balancing immobilisation effectiveness with potential side effects. We compared the immobilisation effectiveness and changes to physiological variables induced by three drug combinations used for free-ranging African lions. The lions (12 animals per drug combination) were immobilised with tiletamine-zolazepam-medetomidine (TZM), ketamine-medetomidine (KM) or ketamine-butorphanol-medetomidine (KBM). Induction, immobilisation, and recovery were timed, evaluated using a scoring system, and physiological variables were monitored. The drugs used for immobilisation were antagonised with atipamezole and naltrexone. The quality of induction was rated as excellent for all drug combinations and induction times (mean ± SD) did not differ between the groups (10.54 ± 2.67 min for TZM, 10.49 ± 2.63 min for KM, and 11.11 ± 2.91 min for KBM). Immobilisation depth was similar over the immobilisation period in the TZM and KBM groups, and initially light, progressing to deeper in lions administered KM. Heart rate, respiratory rate and peripheral arterial haemoglobin saturation with oxygen were within the expected range for healthy, awake lions in all groups. All lions were severely hypertensive and hyperthermic throughout the immobilisation. Following antagonism of immobilising drugs, lions immobilised with KM and KBM recovered to walking sooner than those immobilised with TZM, at 15.29 ± 10.68 min, 10.88 ± 4.29 min and 29.73 ± 14.46 min, respectively. Only one lion in the KBM group exhibited ataxia during recovery compared to five and four lions in the TZM and KM groups, respectively. All three drug combinations provided smooth inductions and effective immobilisations but resulted in hypertension. KBM had an advantage of allowing for shorter, less ataxic recoveries.

Changes in respiratory function following the intramuscular administration of etorphine to boer goats (Capra hircus).

The physiological effects on respiratory function of etorphine (M99, Logos Agvet) (30 microg/kg) administered intramuscularly were determined in boer goats. The goats were habituated to the experimental procedures so that respiratory function could be determined while the animals stood quietly at rest. This enabled the physiological changes induced by etorphine to be measured and compared with those obtained before administration of the immobilising drug. The effectiveness of diprenorphine (M5050, Logos Agvet) (3 mg/l mg etorphine) as an antagonist of the physiological changes induced by the etorphine treatment was also determined. Etorphine depressed respiratory function, which resulted in a decrease in PaO2 and an increase in PaCO2. These changes were limited and occurred as a result of decreases in respiratory minute volume and alveolar minute ventilation caused by a decrease in respiratory rate. The physiological shunt fraction did not change significantly but there was a significant decrease in percentage physiological dead space ventilation. It was not possible to determine how effectively diprenorphine reversed the respiratory effects due to etorphine.