Abstract

Introduction

With the worldwide development of game farming and wildlife management, increased pressure has been placed on maintaining the health and well being of these farmed and free-ranging animals. In many parts of the world these intensively managed species (often wild ruminants) are those that are prone to capture myopathy and handling stress. Methods to decrease overall morbidity and mortality from these preventable conditions have been explored, in attempts to prevent animal injury and suffering, and economic losses to wildlife managers and producers. One technique for the prevention and reduction of stress during wildlife capture, handling, and translocation has been the use of long-acting neuroleptics.⁵

These tranquilizers were originally developed for treatment of human acute psychoses, and are formulated for intramuscular injection.¹ The active drug is slowly released from an oil depot resulting in prolonged release from the injection site, and therefore prolonged drug effects in the patient. These agents were first explored as a means of decreasing stress and mortality in southern Africa in the mid 1980s in a variety of species, and were found to be highly effective for this purpose.⁵

Previously, there has been little reported use of these drugs in North American wildlife species. This study was designed to evaluate the use of one such neuroleptic, zuclopenthixol acetate (ZPTA, Clopixol-Acuphase®, Lundbeck Canada Inc., Montreal, QC, Canada, H2Y 1N9) to decrease handling stress in wild wapiti (Cervus elaphus). We chose to evaluate this particular drug for several reasons. It has been used with success in many other species,⁵ and approximate dose ranges are known. It is available for extra-label use by veterinarians in Canada, and is formulated for intramuscular administration. In addition, its duration of effect has been found to be approximately 3 days, which we felt would be a useful duration to facilitate many procedures performed on this species in captivity. Finally, this drug has been evaluated previously in farmed red deer in Scotland, and benefits of its use in decreasing stress were reported.^2-4

Methods

Several physiologic variables were assessed in order to characterize stress and activity of wild wapiti during handling. The study protocol was designed to collect data on rectal temperature, heart rate, respiratory rate, complete blood count, serum biochemistry, serum cortisol, blood lactate, venous blood gas status, and subjective stress and activity assessment. By measuring this broad range of parameters, we theorized that we would be able to better characterize the stress of handling, and determine any benefit from treatment with ZPTA. The fieldwork for this project was performed in February of 1999 with wild wapiti from the Duck Mountains and Interlake regions of Manitoba, Canada. The Manitoba Department of Agriculture trapped these animals over the previous month for other purposes. Animals were moved through a handling facility for collection of data. After initial handling, animals randomly received 1 mg/kg of ZPTA administered intramuscularly based on an estimated body weight. Animals were then separated into pens based on their assignment into a treatment or control group, in order to prevent mixing of animals and the risk of untreated animals gaining advantage over treatment animals and causing injury. After 24 hr, animals were again processed for data collection. No handling was conducted at 48 hr, in attempt to minimize handling of the animals and acclimatization to the process. At 72 hr after drug administration, the animals were processed for final data collection. Data were analyzed for normalcy, and were found to have normalized distributions. Paired t-tests were performed to compare data within a treatment or control group across days, and two-sample t-tests were done to compare data between treatment and control groups on a given day. The null hypothesis stated there were no differences between the means for two groups compared in each test. Results were considered significant if P < 0.05.

Results

ZPTA-treated animals were found to be less excited based on subjective observations. These animals were observed to spend more time lying down, feeding, and performing normal grooming behavior during the study period than were the control animals. Physiologic parameters measured over the study were also significantly different between groups. The control animals (c) had elevated rectal temperatures when compared to the ZPTA-treated animals (t) (mean ± SD) (day 2 [c]: 40.6 ± 0.6 ° C vs. [t] 39.0 ± 0.4 ° C) during handling. Control animals also showed elevations in serum cortisol levels (day 2 [c]: 140 ± 44.1 mmol/L vs. [t]: 98 ± 29 mmol/L) and were more hemoconcentrated (increased packed cell volume [day 2 [c]: 0.49 ± 0.03 vs. [t]: 0.42 ± 0.04], hemoglobin concentration [day 2 [c]: 182 ± 7 g/L vs. [t]: 159 ± 11.4 g/L], and red blood cell count [day 2 [c]: 10.43 ± 0.92 X 10¹²/L vs. [t]: 9.19 ± 0.78 X 10¹²/L]), suggesting increased physiologic stress in control animals. Control animals were also more active during handling as reflected in elevated blood lactate levels (day 2 [c]: 6.0 ± 1.49 mmol/L vs. [t]: 3.4 ± 1.17 mmol/L) and a greater degree of acidosis (lower venous blood pH [day 2 [c]: 7.34 ± 0.003 vs. [t]: 7.45 ± 0.02], lower bicarbonate concentration [day 2 [c]: 24 ± 3.1 mmol/L vs. [t]: 29 ± 2.7 mmol/L]). Finally, the only animals found to have evidence of extreme muscular injury (creatine phosphokinase levels > 20,000U/L) based on serum biochemistry were control animals. As demonstrated, there were marked drug effects at 24 hr (day 2) after administration, and the neuroleptic still appeared to be active 3 days after administration, although its effects were waning (data not shown).

All animals survived the study and experienced no major complications. There were no apparent adverse drug effects or abnormal behavioral manifestations noted. No injection site problems were observed.

Discussion

The findings of this study suggest that zuclopenthixol acetate can be used safely at the approximate dose of 1mg/kg in young male wapiti to reduce handling stress. ZPTA-treated animals were much calmer during handling, and measurement of physiologic parameters indicated that these animals had fewer disturbances, potentially making them less prone to capture myopathy. Long-acting neuroleptics (LAN's) are tranquilizers, and as such can be used to decrease anxiety in a subject. These agents are particularly useful during management of wildlife species since the drug formulation permits slow release of the active drug from the site of intramuscular injection. As a result, frequent and repeated dosing is not required. With the decreases in anxiety and panic during handling, animals are less prone to injury.⁵ The outward manifestations of anxiety, stress, and struggle can be minimized by the judicious use of these neuroleptics, but these drugs should never be used as the sole means of controlling stress in animals. Instead, LAN's can be used as an adjunct to careful handling practices. Although the outward signs of struggle and panic can be decreased, often resulting in less injury and death,⁵ animals may still be experiencing significant psychologic stress which we cannot measure objectively. Capture myopathy can develop through several related processes,⁶ and although the ZPTA-treated animals in this study showed less indication of physiologic imbalance and dysfunction than control animals, even neuroleptic-treated animals must be monitored closely for problems. Continued study is necessary to better understand the effects of these agents in wildlife, especially in North America where to date their use has been under-reported.

Acknowledgments

We would like to recognize the generous monetary support of the Agri-Food Innovation Fund, and Lundbeck, Canada for donation of the zuclopenthixol acetate for this study. We also thank K. Isakow and M. Woodbury of the Western College of Veterinary Medicine, and T. Whiting and E. Trout of the Manitoba Department of Agriculture. Finally, we thank L. Janz and the Cottonwood Corner Game Farm for their assistance with handling and use of the facility which allowed us to perform this research.

References

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