Bovine twin birth is associated with detriments including increased embryo/fetal losses, malpresentation and dystocia. Incidence of these is lessened in bilateral compared to unilateral twin pregnancy. This study was undertaken to assess use of follicular ablation by aspiration to create bilateral twin pregnancies in females with genetic potential for ~3.5 ovulations per cycle (Trio allele carriers). In Experiment 1, carriers (n=30) and non-carriers (n=10) were synchronized for ovulation and timed artificial insemination (TAI). Follicles (>5 mm) in excess of one per ovary were aspirated ~16h preceding TAI. Follicle count for females with follicles on only one ovary was reduced to two. Blood was sampled 2 weeks post-TAI to assess progesterone (P4) concentrations; embryo count was determined by ultrasound 6 weeks post-TAI. Circulating P4 concentration post-TAI was significantly (p& 0.001) associated with both genotype and subsequent pregnancy status (pregnant non-carriers, 7.06±0.68ng/mL; pregnant carriers, 5.54±0.55ng/mL; non-pregnant non-carriers 5.22±1.05ng/mL; non-pregnant carriers, 3.13±0.42ng/mL). Experiment 2 was undertaken to offset negative effects of follicular aspiration on subsequent P4 concentration observed in Experiment 1. Carriers (n=38) and non-carriers (n=32) were submitted to TAI and follicle ablation as described for Experiment 1. Additionally, accessory corpora lutea (CL) were induced in carriers by administration of human chorionic gonadotropin (carriers) at d6 post-TAI. Consequently, P4 concentration post-TAI was significantly (p& 0.05) associated with subsequent pregnancy status (pregnant, 8.48±0.61ng/mL; non-pregnant, 6.70±0.63 ng/mL) but not with genotype (carrier, 8.01±0.59 ng/mL; non-carrier, 7.17±0.64 ng/mL). Embryo number was greater in carriers (Exp1, 1.64±0.81; Exp2, 1.45±0.09) vs non-carriers (1.00±0.00, both Experiments). Single, twin, and triplet pregnancies occurred in carriers in Experiment 1 whereas multiples in Experiment 2 were limited to twin pregnancies. Genotype effects on pregnancy rate were not significant (p >0.10) in either experiment. Results suggest that follicular ablation to create bilateral twin pregnancies in Trio carriers is feasible but requires induction of accessory CL to offset the negative effects of follicular aspiration on subsequent P4 concentration and associated fertility outcomes.

中文翻译：

---

不切实际的牛基因型的实际应用；在 Trio 等位基因携带者中创造双胞胎妊娠。

牛双胞胎出生与不利因素有关，包括胚胎/胎儿损失增加、畸形和难产。与单侧双胎妊娠相比，双侧双胎妊娠的发生率降低。本研究旨在评估通过抽吸去除卵泡在具有每个周期约 3.5 次排卵（三等位基因携带者）遗传潜力的女性中产生双胎妊娠的使用。在实验 1 中，携带者 (n=30) 和非携带者 (n=10) 同步排卵和定时人工授精 (TAI)。在 TAI 前约 16 小时，每个卵巢吸出超过 1 个的卵泡（> 5 毫米）。只有一个卵巢上有卵泡的雌性的卵泡数减少到两个。在 TAI 后 2 周采集血液样本以评估孕酮 (P4) 浓度；在 TAI 后 6 周通过超声确定胚胎计数。TAI 后循环 P4 浓度与基因型和随后的妊娠状态显着相关（p& 0.001）（怀孕非携带者，7.06±0.68ng/mL；怀孕携带者，5.54±0.55ng/mL；非妊娠非携带者 5.22 ±1.05ng/mL；非妊娠携带者，3.13±0.42ng/mL）。进行实验 2 以抵消滤泡抽吸对实验 1 中观察到的后续 P4 浓度的负面影响。如实验 1 所述，携带者 (n=38) 和非携带者 (n=32) 接受 TAI 和卵泡消融。此外，通过在 TAI 后第 6 天施用人绒毛膜促性腺激素（载体）在载体中诱导副黄体（CL）。因此，TAI 后的 P4 浓度与随后的妊娠状态（妊娠，8.48±0.61ng/mL；非妊娠，6.70±0）显着相关（p&0.05）。63 ng/mL），但与基因型无关（载体，8.01±0.59 ng/mL；非载体，7.17±0.64 ng/mL）。与非携带者（1.00±0.00，两个实验）相比，携带者（Exp1，1.64±0.81；Exp2，1.45±0.09）中的胚胎数量更多。单胞胎、双胞胎和三胞胎妊娠发生在实验 1 中的携带者中，而实验 2 中的多胞胎仅限于双胞胎妊娠。在任一实验中，基因型对妊娠率的影响均不显着（p > 0.10）。结果表明，在 Trio 携带者中进行卵泡消融以产生双胎妊娠是可行的，但需要诱导辅助 CL 以抵消卵泡抽吸对后续 P4 浓度和相关生育结果的负面影响。45±0.09）与非携带者（1.00±0.00，两个实验）。单胞胎、双胞胎和三胞胎妊娠发生在实验 1 中的携带者中，而实验 2 中的多胞胎仅限于双胞胎妊娠。在任一实验中，基因型对妊娠率的影响均不显着（p > 0.10）。结果表明，在 Trio 携带者中进行卵泡消融以产生双胎妊娠是可行的，但需要诱导辅助 CL 以抵消卵泡抽吸对后续 P4 浓度和相关生育结果的负面影响。45±0.09）与非携带者（1.00±0.00，两个实验）。单胞胎、双胞胎和三胞胎妊娠发生在实验 1 中的携带者中，而实验 2 中的多胞胎仅限于双胞胎妊娠。在任一实验中，基因型对妊娠率的影响均不显着（p > 0.10）。结果表明，在 Trio 携带者中进行卵泡消融以产生双胎妊娠是可行的，但需要诱导辅助 CL 以抵消卵泡抽吸对后续 P4 浓度和相关生育结果的负面影响。