Chemical capture of free-ranging cattle: immobilization with xylazine or medetomidine, and reversal with atipamezole

Determination of Embryotoxic effects of Atipamezole using in ovo model

Atipamezole is a specific α2-adrenergic receptor antagonist, and there exists insufficient information on its use during pregnancy. The aim of this study was to determine the embryotoxic activity of Atipamezole through an in ovo method. During the first stage of the study, 210 fertile eggs were divided into seven groups of 30 fertile eggs and placed in an incubator. On the seventh day of the first stage, no application was made to the control group. The second group was administered 50 microliters (µL) of saline solution, while the other groups were given Atipamezole at doses of 250, 125, 62.5, 31.25 and 15.62 micrograms·egg-1 (µg·egg-1) in 50 µL saline solution. In the second stage, according to the embryotoxic dose range determined from the first stage, 150 fertile eggs were divided into five groups of 30 fertile eggs and placed in an incubator. On the seventh day of the second stage, no application was made to the control group. Fifty µL of saline solution was administered to the second group. The other groups were given Atipamezole at doses of 220, 190 and 160 µg·egg-1 in 50 µL saline solution. After the incubation period, the eggs hatched, and the embryonic mortality rates were calculated. The mortality rate was determined to be 39.3% at the highest dose (250 µg·egg-1 = 5 miligrams·kilograms-1 –mg·kg-1–) (P<0.05), while the mortality rate at other doses was determined to be the same as the control group (P>0.05). In conclusion, it can be stated that the dose determined for Atipamezole in this study was very high compared to the recommended doses and it can be used in pregnancy as a benefit-loss calculation when necessary. However molecular or histopathological studies regarding the development of organ drafts are necessary to determine the safety of its use during pregnancy.

Reversal of epidural xylazine in Egyptian water buffalo (Bubalus bubalis) with atipamezole

The reversal of epidural xylazine, induced with IV atipamezole was evaluated in 15 buffaloes. Atipamezole at different dose rates (5, 10 and 15 µg/kg) injected 30 minutes after epidural xylazine provoked visible signs of arousal shortly after inection in all buffaloes without any side effects. The mean arousal times were 4.8±0.84 min, 2.4±0.24 min and 2.0±0.00 min while the mean total recovery times were 61.0±2.6 min, 33.0±3.7 min and 32.0±4.3 min following doses of 5, 10 and 15 µg/kg atipamezole respectively. The heart, respiratory and ruminal rates were mildly influenced. Overall, the IV atipamezole at a dose rate of 10 µg/kg was found effective and satisfactory for reversing the analgesic, sedative and cardiopulmonary depression effects induced by epidural xylazine administration in buffaloes.

A review of methods used to capture and restrain introduced wild deer in Australia

Six non-native deer species have established wild populations in Australia, and most are expanding in distribution and abundance. There is therefore increasing focus on the need to understand and manage these species. Capturing and immobilising wild deer is essential for many research and management applications, but the best methods for doing this have not been identified for the Australian situation. To address this knowledge gap, we systematically reviewed methods used to physically capture and chemically immobilise the six wild deer species in Australia. A variety of physical and chemical restraint methods have been used to capture wild deer in Australia, but these have seldom been reported in peer-reviewed publications. Physical capture methods have employed a variety of trapping and netting configurations. Some chemical immobilisation approaches have used oral baiting, but most have relied on darting of free-ranging animals or hand-injection of physically restrained deer. There is uncertainty about the efficacy and animal welfare impacts of the techniques currently used to capture wild deer in Australia. Improved reporting of capture outcomes would facilitate the identification of ‘best practice’ techniques for capturing wild deer in Australian environments.

Remote chemical immobilisation method for free-ranging Australian cattle

BACKGROUND

Many situations are encountered in Australia where the capture and restraint of free-ranging cattle (Bos taurus/Bos indicus) is required. Chemical immobilisation via darting is a potentially useful tool for managing and researching large wild herbivores; however, there is no reliable method for its application to Australian cattle. The aim of this study was to develop an efficacious, humane, cost-effective ground darting method for free-ranging cattle.

METHODS

The 30 female cattle were darted and captured on a pastoral station in north-west Australia from a vehicle. Xylazine (0.59 mg/kg) and ketamine (3.59 mg/kg) were used to capture animals and yohimbine (0.10 mg/kg) was used as an antagonist to xylazine to reduce recumbent time.

RESULTS

Cattle became recumbent at a mean time of 8 min and a mean distance of 260 m from darting. The mortality rate was zero on the day of capture and 7% at 14 days post-capture.

CONCLUSIONS

The majority of darted cattle were successfully immobilised with one dart and recovered within 30 min, with consumables costing approximately A$30 per captured animal. The technique developed represents a rapid and humane method for capturing free-ranging cattle and, with consideration for legislation surrounding use of veterinary chemicals, could be applied in many contexts across Australia.

Chemical immobilisation and rangeland species: assessment of a helicopter darting method for Australian cattle

Chemical immobilisation (darting) is increasingly being used for the capture of rangeland animals. The aim of the present study was to assess a newly developed helicopter-based chemical immobilisation method for free-ranging Australian rangeland cattle (Bos taurus and Bos indicus). Eighteen cattle were darted from a helicopter in north-western Australia in September 2015 using a combination of xylazine and ketamine, partially reversed with yohimbine. Following a recently published framework for assessing helicopter darting methods, we quantified several animal welfare measures designed to quantify the severity and duration of stress imposed by the procedures. The duration of the procedures was generally short (median total duration 41 min), but for 33% of animals total duration exceeded 60 min. Although the sample size was small, mortality rate on the day of capture was 17% (three animals) and 28% (five animals) required physical restraint to achieve recumbency. We describe this newly developed method and discuss its relatively poor animal welfare outcomes compared with other validated helicopter darting methods. Legislation restricts veterinary chemicals that may be used for food-producing species in many countries, including Australia. Chemical immobilisation regimens other than the one chosen in the present study may produce superior animal welfare outcomes but would not be compliant with legislation in Australia. As a result of these restrictions, we suggest that development of an improved helicopter darting method for Australian cattle may prove difficult. Rangeland managers should carefully consider animal welfare impacts before undertaking chemical immobilisation programs, especially for food-producing species.

Effect of medetomidine and its antagonism with atipamezole on stress-related hormones, metabolites, physiologic responses, sedation, and mechanical threshold in goats

OBJECTIVE

To evaluate the effects of medetomidine and its antagonism with atipamezole in goats.

STUDY DESIGN

Prospective randomized crossover study with 1 week between treatments.

ANIMALS

Six healthy 3-year-old neutered goats (three male and three female) weighing 39.1-90.9 kg (60.0 +/- 18 kg, mean +/- SD).

METHODS

Goats were given medetomidine (20 microg kg(-1), IV) followed, 25 minutes later, by either atipamezole (100 microg kg(-1), IV) or saline. Heart and respiratory rate, rectal temperature, indirect blood pressure, and mechanical threshold were measured, and sedation and posture were scored and blood samples obtained to measure epinephrine, norepinephrine, free fatty acids, glucose, and cortisol concentrations at baseline (immediately before medetomidine), 5 and 25 minutes after medetomidine administration, and at 5, 30, 60, and 120 minutes after the administration of antagonist or saline. Parametric and nonparametric tests were used to evaluate data; p < 0.05 was considered significant.

RESULTS

Medetomidine decreased body temperature, heart rate, and respiratory rate and increased mean arterial blood pressure, cortisol, and glucose. Recumbency occurred 89 +/- 50 seconds after medetomidine administration. All goats were standing 86 +/- 24 seconds after atipamezole administration whereas all goats administered saline were sedate and recumbent at 2 hours. Tolerance to compression of the withers and metacarpus increased with medetomidine. From 5 to 120 minutes after saline or atipamezole administration, there were differences in body temperature, glucose, and cortisol but none in heart rate or blood pressure. Three of the six goats receiving saline developed bloat; five of six urinated. After atipamezole, four of six goats developed piloerection and all goats were agitated and vocalized.

CONCLUSION

At the doses used, atipamezole antagonized the effects of medetomidine on recumbency, sedation, mechanical threshold, and the increase in glucose. Atipamezole increased the rate of return of cortisol toward baseline, and prevented further decline in rectal body temperature.

CLINICAL RELEVANCE

Atipamezole may be used to antagonize some, but not all effects of medetomidine.

A pharmacokinetic study including some relevant clinical effect of medetomidine and atipamezole in lactating dairy cows

Medetomidine is the most potent and selective alpha2-agonist used in veterinary medicine and its effects can be antagonized by the alpha2-antagonist atipamezole. The pharmacokinetics of medetomidine and atipamezole were studied in a cross-over trial in eight lactating dairy cows. The animals were injected intravenously (i.v.) with medetomidine (40 microg/kg) followed by atipamezole i.v. (200 microg/kg) or saline i.v. after 60 min. Drug concentrations in plasma were measured by HPLC. After the injection of atipamezole, the concentration of medetomidine in plasma increased slightly, the mean increment being 2.7 ng/mL and the mean duration 12.1 min. However, atipamezole did not alter the pharmacokinetics of medetomidine. It is likely that the increase in medetomidine concentration is caused by displacement of medetomidine by atipamezole in highly perfused tissues. The volume of distribution at steady state (Vss) for medetomidine followed by saline and medetomidine followed by atipamezole was 1.21 and 1.32 L/kg, respectively, whereas the total clearance (Cl) values were 24.2 and 25.8 mL/min x kg. Vss and Cl values for atipamezole were 1.77 mL/kg and 48.1 mL/min x kg, respectively. Clinically, medetomidine significantly reduced heart rate and increased rectal temperature for 45 min. Atipamezole reversed the sedative effects of medetomidine. However, all the animals, except one, relapsed into sedation at an average of 80 min after injection of the antagonist.

Food intake and rumen motility in dwarf goats. Effects of atipamezole on the inhibitory effects induced by detomidine, medetomidine and romifidine

The effects of some alpha 2-adrenoceptor agonists and of the alpha 2-adrenoceptor antagonist atipamezole on food intake and ruminal contractions were studied in dwarf goats. Detomidine, 0.2 microgram/kg per min for 10 min, failed to modify food intake during either the first or second observation period (0-30 min and 180-210 min after drug infusion, respectively). Given at a higher dose rate (0.4 microgram/kg per min for 10 min), the drug inhibited food consumption during the first observation period, but stimulated food intake during the second period. A similar pattern was observed after IV infusion with medetomidine (0.2 microgram/kg per min for 10 min), romifidine (0.4 microgram/kg per min for 10 min) or xylazine (1 microgram/kg per min for 10 min). The alpha 2-antagonist atipamezole (2 micrograms/kg per min for 10 min) failed to modify food intake during either the first or second observation period. After treatment with atipamezole, the effects of alpha 2-agonists on feeding behaviour were completely antagonized. The alpha 2-agonists administered at similar dose rates to those used in the food intake experiments induced bradycardia, decreases in body temperature and inhibition of ruminal contractions. The inhibition of ruminal contractions induced by romifidine was partly antagonized by atipamezole pre-treatment. These findings demonstrate that the alpha 2-agonist-induced changes in ruminal contractions do not simply cause changes in feeding behaviour. The drop in body temperature induced by alpha 2-agonists was prevented by atipamezole pre-treatment, whereas the induced bradycardia was not modified by this alpha 2-antagonist.