Ketamine-butorphanol-medetomidine versus butorphanol-midazolam-medetomidine immobilisation of serval (Leptailurus serval)

Abstract

Objective To compare ketamine-butorphanol-medetomidine (KBM) to butorphanolmidazolam- medetomidine (BMM) for chemical capture (immobilisation) of serval (Leptailurus serval). Study design Blinded, randomised immobilisation trial. Animals 23 free-ranging captures (KBM: 5 females, 6 males; mean weight 10.7 kg; BMM: 10 females, 2 males; mean weight 9.6 kg). Methods Free-ranging serval were cage trapped and then immobilised using the randomly assigned drug combination delivered via a blow dart into the gluteal muscles. Prior to darting, a stress score was assigned (0: Calm; to 3: markedly stressed). The drug combinations were dosed based on estimated body weights: KBM - 8.0, 0.4 and 0.08 mg kg-1, respectively; BMM - 0.4, 0.3 and 0.08 mg kg-1, respectively. Time to first handling, duration of anaesthesia and recovery times were recorded. Physiological variables were recorded at five-minute intervals and arterial blood was sampled 20 minutes after instrumentation for arterial blood gas analysis. Atipamezole (5 mg kg-1 medetomidine) and naltrexone (2 mg kg-1 butorphanol) were administered intramuscularly for recovery. Data, presented using mean ± standard deviation values, were analysed using student t-test, general linear mixed model and Spearman’s rank correlation. Results The dose based on actual body weights were 8.7 ± 1.5, 0.4 ± 0.08 and 0.09 ± 0.02 mg kg-1 for KBM; and 0.5 ± 0.07, 0.4 ± 0.01 and 0.09 ± 0.05 mg kg-1 for BMM. Time to first handling was 611 ± 165 seconds for KBM and 800 ± 228 seconds for BMM (p = 0.033). Both combinations produced a physiological stable immobilisation that lasted for at least 35 minutes. Recovery was rapid and calm overall, but ataxia was noted in KBM. Stress score was positively and strongly correlated to blood glucose (r2 = 0.788; p = 0.001) and temperature (r2 = 0.634; p = 0.015). Conclusion and clinical relevance Both combinations produce similar effective immobilisation that were physiologically stable in serval. Overall, BMM is recommended because it is fully antagonisable. It is essential to provide a calm, quiet environment before drug administration to avoid capture-induced hyperglycaemia and hyperthermia.