Meuffels Janine, Bertschinger Henk, Tindall Brendan, Pohlin Friederike, Luther-Binoir Ilse, Trivedi Shweta, Boshoff Christiaan R, Lueders Imke
Cryovault, Hemmersbach Rhino Force NCP, Hoedspruit, South Africa.
Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
Front Vet Sci. 2022 Apr 27;9:862100. doi: 10.3389/fvets.2022.862100. eCollection 2022.
With the rapid loss of individuals in the wild, semen cryopreservation has gained importance to safeguard the genetic diversity of white rhinoceroses (). For semen collection electro-ejaculation, immobilization of free-ranging individuals requires the potent opioid etorphine, which is routinely combined with azaperone, but causes hypoxemia, hypercarbia, acidemia, muscle rigidity, tachycardia, and systemic hypertension. In this study, the suitability of two alternative immobilization protocols including etorphine, medetomidine, and midazolam at different doses (high vs. low etorphine) was evaluated in adult white rhinoceros bulls in two different management systems (free-ranging vs. game-farmed) and undergoing electro-ejaculation. Fourteen free-ranging (Group 1) and 28 game-farmed rhinoceroses (Group 2) were immobilized with ≈2.5 μg/kg etorphine (high dose), ≈2.5 μg/kg medetomidine, ≈25 μg/kg midazolam and 1,500-1,700 IU hyaluronidase and received ≈2.5 μg/kg of butorphanol intravenously at first handling. Twenty game-farmed animals (Group 3) received ≈1 μg/kg etorphine (low dose), ≈5 μg/kg medetomidine, ≈25 μg/kg midazolam and 1,700 IU hyaluronidase. Respiratory rate, heart rate and peripheral hemoglobin oxygen saturation (SpO) were measured at 5-min intervals; non-invasive oscillometric blood pressures and arterial blood gases at first handling and before reversal of the immobilization; serum clinical chemistry analytes and hematocrit at first handling. Generalized mixed models (fixed factors: group, time, recumbency; random factor: individual rhinoceros) were applied to compare longitudinal changes between free-ranging and game-farmed rhinoceroses immobilized with the higher etorphine dose (Groups 1 and 2), and between the two protocols tested in the game-farmed rhinoceroses (Groups 2 and 3). All animals were successfully immobilized, presented with normal lactate concentrations (<5 mmol/L), experienced no muscle tremors and recovered uneventfully. Hypoxemia and hypertension persisted throughout the immobilization in all groups. Acidemia and hypercarbia were absent in Group 1, but present in the game-farmed animals. The lower etorphine dose in Group 3 resulted in significantly longer induction times, however, tachycardia was not observed. SpO was higher for sternal vs. lateral recumbency. Semen-rich fractions were recovered following electro-stimulation in 46 out of the 62 animals. Our findings suggest that etorphine-medetomidine-midazolam provides effective immobilization with fewer side effects compared to previous reports in white rhinoceroses and is suitable for successful electro-ejaculation.
随着野生白犀牛个体数量的迅速减少，精液冷冻保存对于保护白犀牛的遗传多样性变得至关重要。对于精液采集，采用电刺激采精时，需要使用强效阿片类药物埃托啡对自由放养的个体进行麻醉，该药物通常与阿扎哌隆联合使用，但会导致低氧血症、高碳酸血症、酸血症、肌肉僵硬、心动过速和全身性高血压。在本研究中，评估了两种替代麻醉方案（包括不同剂量的埃托啡、美托咪定和咪达唑仑，高剂量埃托啡与低剂量埃托啡对比）在两种不同管理系统（自由放养与圈养）中对成年雄性白犀牛进行电刺激采精时的适用性。14头自由放养的白犀牛（第1组）和28头圈养的白犀牛（第2组）用约2.5μg/kg埃托啡（高剂量）、约2.5μg/kg美托咪定、约25μg/kg咪达唑仑和1500 - 1700IU透明质酸酶进行麻醉，并在初次处理时静脉注射约2.5μg/kg布托啡诺。20头圈养动物（第3组）接受约1μg/kg埃托啡（低剂量）、约5μg/kg美托咪定、约25μg/kg咪达唑仑和1700IU透明质酸酶。每隔5分钟测量呼吸频率、心率和外周血红蛋白氧饱和度（SpO）；在初次处理和麻醉解除前测量无创示波血压和动脉血气；在初次处理时测量血清临床化学分析物和血细胞比容。应用广义混合模型（固定因素：组、时间、卧位；随机因素：个体犀牛）来比较自由放养和圈养的用较高剂量埃托啡麻醉的白犀牛（第1组和第2组）之间的纵向变化，以及圈养白犀牛中测试的两种方案（第2组和第3组）之间的纵向变化。所有动物均成功麻醉，乳酸浓度正常（<5mmol/L），未出现肌肉震颤，恢复顺利。所有组在整个麻醉过程中均持续存在低氧血症和高血压。第1组未出现酸血症和高碳酸血症，但圈养动物中存在。第3组较低剂量的埃托啡导致诱导时间显著延长，然而未观察到心动过速。胸骨卧位时的SpO高于侧卧位。62头动物中有46头在电刺激后采集到了富含精液的部分。我们的研究结果表明，与之前关于白犀牛的报道相比，埃托啡 - 美托咪定 - 咪达唑仑提供了有效的麻醉且副作用更少，适用于成功的电刺激采精。
