Data_Sheet_1_Arterial Blood Gases and Cardiorespiratory Parameters in Etorphine-Medetomidine-Midazolam Immobilized Free-Ranging and Game-Farmed Southern White Rhinoceroses (Ceratotherium simum simum) Undergoing Electro-Ejaculation.docx

With the rapid loss of individuals in the wild, semen cryopreservation has gained importance to safeguard the genetic diversity of white rhinoceroses (Ceratotherium simum). For semen collection via 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 (SpO2) 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. SpO2 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.

随着野外个体的快速减少，精液冷冻保存（semen cryopreservation）对保护白犀牛（Ceratotherium simum）的遗传多样性愈发重要。针对电刺激采精（electro-ejaculation）所需的野外散养个体保定（immobilization），常规需使用强效阿片类药物埃托啡（etorphine），该药物常与阿扎哌隆（azaperone）联合使用，但会引发低氧血症（hypoxemia）、高碳酸血症（hypercarbia）、酸血症（acidemia）、肌肉强直（muscle rigidity）、心动过速（tachycardia）及全身性高血压（systemic hypertension）等不良反应。本研究针对成年雄性白犀牛，在两种饲养管理系统（野外散养vs人工圈养繁育）下，采用不同剂量埃托啡（高剂量vs低剂量）的埃托啡-美托咪定（medetomidine）-咪达唑仑（midazolam）两种替代保定方案，开展电刺激采精的适用性评估。本研究纳入14头野外散养犀牛（组1）及28头人工圈养繁育犀牛（组2），均采用≈2.5 μg/kg埃托啡（高剂量）、≈2.5 μg/kg美托咪定、≈25 μg/kg咪达唑仑、1500~1700 IU透明质酸酶（hyaluronidase）进行保定，并在首次操作时静脉注射≈2.5 μg/kg布托啡诺（butorphanol）。另有20头人工圈养繁育犀牛（组3）采用≈1 μg/kg埃托啡（低剂量）、≈5 μg/kg美托咪定、≈25 μg/kg咪达唑仑及1700 IU透明质酸酶进行保定。研究人员每5分钟记录一次呼吸频率、心率及外周血红蛋白氧饱和度（SpO2）；在首次操作时及保定逆转前，检测无创示波血压（non-invasive oscillometric blood pressures）与动脉血气（arterial blood gases）；在首次操作时采集血清临床生化指标（serum clinical chemistry analytes）与血细胞比容（hematocrit）。采用广义混合模型（Generalized mixed models），以组、时间、卧姿（recumbency）为固定因子（fixed factors），以个体犀牛为随机因子（random factor），对比野外散养与高剂量埃托啡保定的人工圈养犀牛（组1与组2）的纵向变化（longitudinal changes），以及人工圈养犀牛中两种保定方案的差异（组2与组3）。所有受试动物均成功保定，乳酸浓度正常（<5 mmol/L），未出现肌肉震颤，且顺利苏醒。各组保定全程均存在低氧血症与高血压。组1未出现酸血症与高碳酸血症，但人工圈养繁育犀牛均出现上述异常。组3采用的低剂量埃托啡方案诱导时间显著更长，但未引发心动过速。胸骨卧位的SpO2高于侧卧位。62头受试犀牛中，46头经电刺激采集到富含精液的组分（semen-rich fractions）。本研究结果表明，埃托啡-美托咪定-咪达唑仑联合方案相较既往白犀牛保定报道的不良反应更少，可实现有效的保定并成功完成电刺激采精。