Campbell A J, Pearson L K, Spencer T E, Tibary A
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA; Center for Reproductive Biology, Washington State University, Pullman, Washington, USA.
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA; Center for Reproductive Biology, Washington State University, Pullman, Washington, USA.
Theriogenology. 2015 Aug;84(3):421-4. doi: 10.1016/j.theriogenology.2015.03.027. Epub 2015 Mar 31.
Twin births are rare in alpacas despite the high incidence of double ovulation and are undesirable because they contribute to early and late pregnancy loss, abortion, and birth of nonviable neonates. The objective of the present study was to determine the incidence and outcome of twin pregnancy in double-ovulating alpacas by retrospective and prospective analysis. Data from double-ovulating females (N = 41) presented for pregnancy diagnosis were analyzed to determine pregnancy status at three stages after mating (14-16, 25-30, and 45-53 days). In a prospective study, adult reproductively sound alpacas (n = 21) were examined by ultrasonography to determine the incidence of multiple ovulations. A subset of those alpacas (n = 10) were euthanized either at 9 days (n = 5) or 14 days (n = 5) after a single mating and administration of GnRH to determine presence and number of embryos. A total of 31 cycles were included in the study to determine the incidence of multiple ovulations. In the retrospective study, twin pregnancies were identified between 25 and 30 days in 47.1% of double-ovulating females. There were more twins from bilateral ovulations (62.5%) than from unilateral ovulations (37.5%). Twin pregnancies were either reduced to a singleton (62.5%) or lost completely (37.5%). One set of twins remained viable until Day 52. In the prospective study, double ovulation occurred in 18.8% of the cycles. Two embryos were collected from two of the four double-ovulating females. In conclusion, twin conception is not rare in alpacas. A high rate of spontaneous reduction of twin pregnancies occurs before Day 45. However, a significant proportion of twin pregnancy may result in loss of both embryos. Determination of the number of ovulations (CL) at the time of early pregnancy diagnosis (14-16 days) should be an integral part of any pregnancy evaluation.
尽管羊驼双排卵的发生率很高，但双胎分娩却很罕见，而且是不理想的，因为双胎会导致早期和晚期妊娠丢失、流产以及产出无法存活的新生儿。本研究的目的是通过回顾性和前瞻性分析来确定双排卵羊驼双胎妊娠的发生率和结局。对前来进行妊娠诊断的双排卵雌性羊驼（N = 41）的数据进行分析，以确定交配后三个阶段（14 - 16天、25 - 30天和45 - 53天）的妊娠状态。在一项前瞻性研究中，通过超声检查对成年生殖功能健全的羊驼（n = 21）进行检查，以确定多排卵的发生率。这些羊驼中的一部分（n = 10）在单次交配并注射促性腺激素释放激素（GnRH）后的第9天（n = 5）或第14天（n = 5）实施安乐死，以确定胚胎的存在情况和数量。共有31个周期纳入研究以确定多排卵的发生率。在回顾性研究中，47.1%的双排卵雌性羊驼在25至30天之间被确定为双胎妊娠。双侧排卵的双胎（62.5%）比单侧排卵的双胎（37.5%）更多。双胎妊娠要么减少为单胎（62.5%），要么完全丢失（37.5%）。有一组双胞胎存活到了第52天。在前瞻性研究中，18.8%的周期出现双排卵。在四个双排卵雌性羊驼中的两个收集到了两个胚胎。总之，羊驼双胎受孕并不罕见。双胎妊娠在第45天之前有很高的自然减少率。然而，相当一部分双胎妊娠可能导致两个胚胎都丢失。在早期妊娠诊断时（14 - 16天）确定排卵（黄体）数量应是任何妊娠评估不可或缺的一部分。
