Relative efficiency of succinylcholine, xylazine, and carfentanil/xylazine mixtures to immobilize free-ranging moose

Underaddressed animal-welfare issues in conservation

Much progress has been made toward assessing and improving animal welfare in conservation. However, several glaring knowledge gaps remain where animal-welfare concerns exist but animal-welfare studies have not been performed in politically sensitive contexts. Based on contemporary issues in Australia, we identified 4 topics that require more research: animal-welfare oversight for operations designated as management (as opposed to research); animal-welfare impacts of biological agents used to control invasive animals; welfare of animals hunted recreationally; and animal-welfare impacts associated with indigenous wildlife use. Animal-welfare science may be applied to these sensitive topics through simple quantitative studies (e.g., quantifying the frequency of adverse animal-welfare events). Several such studies have effectively addressed animal-welfare concerns in similarly contentious contexts, including feral camel (Camelus dromedarius) culling in Australia, recreational hunting in Scandinavia, and indigenous whale hunting in the United States. For discussions of animal welfare in conservation to be evidence-based, courageous research is required in the 4 key areas we identified.

Assessing the efficacy of medetomidine and tiletamine–zolazepam for remote immobilisation of feral horses (Equus caballus)

Context The study of any wild animal’s home range requires the collection of spatiotemporal data, obtained independently of climatic conditions or time of day. This can be achieved by the attachment of global positioning system (GPS) data loggers, which, in large species, is best achieved by remote immobilisation. Feral horses (Equus caballus) usually occupy remote areas of Australia; however, a considerable population increase has been observed in a close proximity to metropolitan areas of the Australian east coast, creating increasing conflict with human interests. Aim The aim of the present study was to investigate the efficacy of remote chemical immobilisation of feral horses with medetomidine combined with tiletamine–zolazepam to facilitate placement of satellite GPS collars. Methods Nine feral horses were darted from the ground with 60 mg (i.m.) medetomidine and 1500 mg (i.m.) tiletamine–zolazepam. The effects of medetomidine were reversed with 50–100 mg (i.m. or i.v.) atipamezole 30–40 min after induction (IV/IM). Physiological variables monitored during anaesthesia were heart rate, respiratory rate, temperature and oxygen haemoglobin saturation (Spo2). Key results All horses were successfully immobilised with between one and three darts (n = 9). The mean (± s.e.m.) dose of medetomidine was 0.15 ± 0.01 mg kg–1, whereas that of tiletamine–zolazepam was 3.61 ± 0.16 mg kg–1. Mean time from darting to lateral recumbency was 13.3 ± 2.7 min and mean recumbency time was 54 ± 13 min. Vital signs for all anaesthetised animals remained within the normal range during anaesthesia, with the exception of one animal exhibiting a transient drop in Spo2. There were no deaths. Key conclusions The combination of medetomidine and tiletamine–zolazepam provided adequate anaesthesia in feral horses in the field for application of GPS collars. Implications Although a limited number of horses was immobilised, the present study shows that the combination of medetomidine and tiletamine–zolazepam provides effective short-term anaesthesia for feral horses, affording a practical and field-accessible capture technique. This method could also be applied to other management actions requiring the safe and humane capture of feral horses.

Physiological evaluation of free-ranging moose (Alces alces) immobilized with etorphine-xylazine-acepromazine in Northern Sweden

Background

Evaluation of physiology during capture and anesthesia of free-ranging wildlife is useful for determining the effect that capture methods have on both ecological research results and animal welfare. This study evaluates capture and anesthesia of moose (Alces alces) with etorphine-xylazine-acepromazine in Northern Sweden.

Methods

Fifteen adult moose aged 3–15 years were darted from a helicopter with a combination of 3.37 mg etorphine, 75 mg xylazine, and 15 mg acepromazine. Paired arterial blood samples were collected 15 minutes apart with the first sample at 15–23 minutes after darting and were analyzed immediately with an i-STAT®1 Portable Clinical Analyzer.

Results

All animals developed hypoxemia (PaO₂ <10 kPa) with nine animals having marked hypoxemia (PaO₂ 5.5-8 kPa). All moose were acidemic (ph<7.35) with nine moose having marked acidemia (pH<7.20). For PaCO_2, 14 moose had mild hypercapnia (PaCO₂ 6-8 kPa) and two had marked hypercapnia (PaCO₂>8 kPa). Pulse, respiratory rate, pH and HCO₃ increased significantly over time from darting whereas lactate decreased.

Conclusions

The hypoxemia found in this study is a strong indication for investigating alternative drug doses or combinations or treatment with supplemental oxygen.

Sedation and chemical restraint of deer

This review examines the properties of chemical immobilising agents of use or potential use in deer for velvet antler removal. The alpha-2-adrenergic agonist, xylazine, is the most commonly used agent for chemical restraint of stags for this purpose in New Zealand. This compound is often combined with an opioid or ketamine to enhance its effectiveness. Concerns about the carcinogenic potential of a xylazine metabolite have led to a call by the deer industry to limit the use of this drug and stimulated enquiry into alternatives. The potent pure opioid agonists, fentanyl, carfentanil and etorphine, are less effective than xylazine when used alone, and their use presents greater risk to operators and animals and is subject to more stringent legal restrictions. Newer alpha-2-adrenergic agonists, detomidine and medetomidine, are more potent than xylazine and unlikely to result in carcinogenic metabolites. Availability of specific alpha-2-adrenergic antagonists further enhances the usefulness of these drugs. The dissociative agent, ketamine, has proven useful for immobilisation of various domestic and wildlife species and captive species of deer but undesirable side effects and the low concentration, relative to the effective dose, of currently available formulations limit its usefulness. Combination of a dissociative agent with an alpha-2-adrenergic agent reduces the required dose of both and enhances their efficacy. A commercially available combination of the dissociative anaesthetic agent, tiletamine, and the benzodiazepine, zolazepam, is more potent than ketamine and induction times are faster. This combination can be manipulated to varying concentrations by dissolution with alpha-2-adrenergic agents. A long-acting neuroleptic agent, zuclopenthixol, has recently been investigated for calming deer and may be an alternative to classical sedative-immobilising agents. Most chemical immobilisation agents used alone or in combination produce respiratory depression and supplemental oxygen has been recommended. All would likely result in some form of chemical residues in velvet antler.

Pharmacokinetics and pharmacodynamics of carfentanil and naltrexone in female common eland (Taurotragus oryx)

The pharmacokinetic parameters of carfentanil and naltrexone were determined in the common eland (Taurotragus oryx). Six adult females were immobilized with xylazine (0.23 +/- 0.03 mg/kg i.m.) and carfentanil (0.0169 +/- 0.0005 mg/kg i.m.) for a 45-min period, during which time routine health care procedures were performed. Heart and respiration rates and body temperatures were monitored throughout the immobilization period. A single intramuscular injection of naltrexone (1.66 +/- 0.08 mg/kg i.m.) was sufficient for reversal. The eland were intermittently restrained in a hydraulic squeeze chute for serial blood sample collection via jugular venipuncture during immobilization and up to 48 hr post-immobilization. The quantification of carfentanil and naltrexone in the plasma was performed by liquid chromatography and mass spectroscopy methods. Carfentanil was rapidly absorbed following administration, with the peak plasma concentration (C(max)) at 13.8 min. Naltrexone was readily absorbed and reached C(max) at 23.4 +/- 16.8 min after administration. All animals stood 2.7 +/- 2.2 min after naltrexone administration. Carfentanil has a half-life of 7.7 hr, whereas naltrexone has a much shorter half-life of 3.7 hr. Although respiratory rates appeared to fluctuate widely among animals, heart rates and body temperature remained stable throughout the immobilization. Renarcotization was not noted as a major complication.

Space use of moose in relation to food availability

We assessed the influence of temporal and spatial changes in food availability on home-range size and movements of moose (Alces alces (L., 1758)). Ten adult moose were radio-collared and monitored with GPS telemetry collars during two contrasting time periods based on food quality and availability: summer (growing period) and winter (dormant and snowy period). According to the habitat productivity – home-range size hypothesis, we expected home-range size and movement rate to be negatively correlated with the proportion of food-rich habitat types in home ranges. Food availability influenced space use, but the effect was more pronounced at the small scale (i.e., movement rates) than at the large scale (i.e., home-range sizes) and during winter than summer. The negative relationship between food availability and home-range size only existed in winter, but movement rates were lower in food-rich habitat types in both time periods. Our results suggested that body size was not the primary factor governing sex-related differences in space use which were likely more related to specific needs of females with regard to the feeding and protection of calves. We suggest that the habitat productivity – home-range size hypothesis may not always be supported when forage is widely distributed and that movement rates can be a better index of forage availability than home-range sizes in such situations.