Abstract:
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.
