CHEMICAL CAPTURE OF FREE-RANGING CATTLE - IMMOBILIZATION WITH XYLAZINE OR MEDETOMIDINE, AND REVERSAL WITH ATIPAMEZOLE

Twenty-nine free-ranging Norwegian cattle were captured with xylazine (n=20) or medetomidine (n=9) using a tranquilizing gun, and the time f rom darting to recumbency (induction time) was recorded. Twenty-eight animals were given atipamezole IV 15-100 min after darting, and the ef fects of the antagonist were evaluated. Blood samples (r.=19) for haem atology and serum chemistry were collected within 10 min after immobil ization was induced. Xylazine (0.55 +/- 0.18 mg/kg; mean +/- SD; n=18) or medetomidine-HCl (0.039 +/- 0.10 mg/kg;, n=8) induced complete imm obilization after a single darting with sternal or lateral recumbency, the induction times being 9.6 +/- 3.8 and 12.0 +/- 6.8 min, respectiv ely. No difference in the clinical effects of the two drugs was observ ed. Rapid reversal was achieved with 0.057 +/- 0.017 and 0.077 +/- 0.0 19 mg/kg of atipamezole-HCl in xylazine- and medetomidine-treated anim als, respectively. All the animals stood within 2 min after IV adminis tration of the antagonist. Seven animals showed signs of excitement sh ortly after reversal, but these side-effects were of brief duration. H eavy resedation with relapse into recumbency was seen 3-4 h after reve rsal in two cows captured with xylazine, while moderate resedation was observed in two medetomidine-treated animals 2 h after reversal. Exce pt for the plasma glucose concentration, which was elevated in both xy lazine- and medetomidine-treated animals, the mean values of the haema tological and plasma chemical parameters were within the reference ran ges established for Nonvegian cattle. Eight cows captured with xylazin e (0.51 +/- 0.20 mg/kg) and given atipamezole-HCl (0.045 +/- 0.013 mg/ kg) for reversal were in the last two months of pregnancy. All these a nimals calved normally and no cases of premature births or other perip arturient disorders were seen.