Field immobilization and euthanasia of American opossum

Seventeen recently trapped opossum, Didelphis virginiana, (median weight 2. 45 kg; range = 1.6-5.0 kg; quartiles = 1.8-3.3 kg) were immobilized with ei ther telazol (15 or 30 mg/kg) or a mixture of medetornidine (100 mu g/kg), butorphanol (0.2 mg/kg), and ketamine HCl (10 mg/kg) based on estimated wei ghts. Anesthetized animals were subjected to cardiac puncture for blood wit hdrawal and toe pinch. Euthanasia was accomplished by intracardiac administ ration of 1 mi of concentrated pentobarbital sodium/phenytoin solution. Wei ghts were underestimated for 14 of 17 animals, but were within 0.5 kg of th e actual weight. Both drug combinations provided rapid and calm immobilizat ion. Median time to recumbency for the medetomidine-butorphanol-ketamine gr oup (n = 5) was 6 min (range = 4-10 min; quartiles = 6 and 8 min). The medi an time to recumbency was not statistically different for the low (n = 6) a nd high dose (n = 6) telazol groups, 3 and 3.5 min respectively (quartiles 3; 3.5 and 4; 5.5 min). The stronger heart beat with telazol immobilization facilitated cardiac puncture. All five animals administered the medetomidi ne-butorphanol-ketamine mixture and three of six animals given the low tela zol dose reacted to cardiac puncture. Only one of six animals given the est imated 30 mg/kg dose of telazol reacted slightly to cardiac puncture. We co nclude that 30 mg/kg telazol provides sufficient immobilization and analges ia to allow accurate cardiac puncture of the opossum if the procedure is pe rformed within 5 to 10 min of recumbency. Intracardiac administration of co ncentrated pentobarbital sodium/phenytoin solution followed by bilateral th oracotomy provides appropriate euthanasia suitable for field situations.