Two experiments were conducted to evaluate the effects of the timing of artificial insemination (AI) and incorporation of the Slo3 K⁺ channel blocker 4-(4-chlorophenyl)butyl-diethyl-heptylammonium to semen extender (CSE) on pregnancy per AI (P/AI) and pregnancy loss in dairy heifers. In experiment 1, Holstein heifers were subjected to the 5-d CIDR-Synch protocol: d −8 GnRH and controlled internal drug-release device (CIDR); d −3 PGF_2α and CIDR removal; d −2 PGF_2α; d 0 GnRH) and assigned randomly to receive timed AI with control semen on d 0 (72-CON; n = 104), control semen on d −1 (48-CON; n = 100), or CSE-treated semen on d −1 (48-CSE; n = 98). Heifers were fitted with collar-mounted automated estrus detection devices to monitor physical activity and rumination. In experiment 2, Holstein heifers were subjected to the 5-d CIDR-Synch protocol and received a mount detection patch at the first PGF_2α injection. Heifers detected in estrus before d 0 were inseminated on the same day, whereas those not detected in estrus received the second GnRH injection and timed AI on d 0. Heifers were assigned randomly to receive AI with control (AI-CON; n = 148) or CSE-treated semen (AI-CSE; n = 110). Four bulls with proven fertility were used in both experiments, and ejaculates from each sire were divided and processed as CON or CSE. Pregnancy was diagnosed by transrectal ultrasonography at 29 and 54 d after AI. Data were analyzed by logistic regression, and statistical models included the fixed effects of treatment and enrollment week. In experiment 1, orthogonal contrasts were built to assess the effects of day of AI (72-CON vs. 48-CON + 48-CSE) and treatment of semen with CSE (48-CON vs. 48-CSE). Pregnancy per AI on d 29 (72-CON = 60.8, 48-CON = 35.2, 48-CSE = 39.8%) and d 54 (72-CON = 58.2, 48-CON = 31.6, 48-CSE = 36.2%) was greater for heifers inseminated on d 0 compared with d −1. However, no effect of semen extender on P/AI was observed in heifers inseminated on d −1. In experiment 2, P/AI tended to be greater for AI-CSE than for AI-CON on d 29 (58.6 vs. 47.3%) and d 54 after AI (55.6 vs. 43.7%). Advancing AI by 24 h decreased the likelihood of pregnancy, and use of CSE was unable to overcome the expected asynchrony between insemination and ovulation. Nevertheless, incorporation of CSE in semen processing tended to improve P/AI when heifers received AI upon detected estrus or timed AI concurrently with the final GnRH of the 5-d CIDR-Synch protocol.

进行了两个实验以评估人工授精（AI）的时机和Slo3 K ⁺通道阻滞剂4-（4-氯苯基）丁基-二乙基庚基铵与精液补充剂（CSE）的结合对每AI怀孕的影响（P / AI）和奶牛的妊娠损失。在实验1中，荷斯坦小母牛接受了5-d CIDR-Synch方案：d -8 GnRH和受控内部药物释放装置（CIDR）；d -3 _PGF2α和CIDR去除；d -2 _PGF2α; d 0 GnRH），并随机分配以接受定时AI，其中d 0为对照精液（72-CON； n = 104），d -1为对照精液（48-CON； n = 100），或d为CSE处理的精液-1（48-CSE； n = 98）。小母牛装配有安装在领子上的自动发情检测设备，以监测身体活动和反刍。在实验2中，小母牛荷斯坦进行5-d CIDR的同步协议和在所述第一PGF接收到安装检测补丁_2α注射。在第0天之前发情的小母牛在同一天进行授精，而在发情中未发现的小母牛在第0天接受第二次GnRH注射和定时AI。将小母牛随机分配为接受对照的AI（AI-CON; n = 148）或经CSE处理的精液（AI-CSE； n = 110）。在两个实验中均使用了四只已证明具有生育力的公牛，将每个父本的射精分开并处理为CON或CSE。AI后29和54 d经直肠超声检查诊断为妊娠。通过逻辑回归分析数据，统计模型包括治疗和入组周的固定影响。在实验1中，建立了正交对比以评估AI日（72-CON对48-CON + 48-CSE）和用CSE治疗精液（48-CON对48-CSE）的效果。第29天（72-CON = 60.8，48-CON = 35.2，与d -1相比，在d 0授精的小母牛的48-CSE = 39.8％）和d 54（72-CON = 58.2，48-CON = 31.6，48-CSE = 36.2％）更大。但是，在d -1授精的小母牛中未观察到精液补充剂对P / AI的影响。在实验2中，AI-CSE的P / AI倾向于比AI-CON大，在第29天（58.6比47.3％）和在AI后第54天（55.6比43.7％）更大。AI提前24小时可降低怀孕的可能性，并且使用CSE无法克服人工授精和排卵之间预期的不同步。然而，当小母牛在检测到发情或定时AI与5-d CIDR-Synch协议的最终GnRH并发时接受AI时，在精液加工中掺入CSE往往会改善P / AI。在d -1授精的小母牛中未观察到精液补充剂对P / AI的影响。在实验2中，AI-CSE的P / AI倾向于比AI-CON大，在第29天（58.6比47.3％）和在AI后第54天（55.6比43.7％）更大。AI提前24小时可降低怀孕的可能性，并且使用CSE无法克服人工授精和排卵之间预期的不同步。然而，当小母牛在检测到发情或定时AI与5-d CIDR-Synch方案的最终GnRH并发时接受AI时，在精液加工中掺入CSE往往会改善P / AI。在d -1授精的小母牛中未观察到精液补充剂对P / AI的影响。在实验2中，AI-CSE的P / AI倾向于比AI-CON在第29天（58.6比47.3％）和在AI后第54天（55.6比43.7％）要大。AI提前24小时可降低怀孕的可能性，并且使用CSE无法克服人工授精和排卵之间预期的不同步。然而，当小母牛在检测到发情或定时AI与5-d CIDR-Synch方案的最终GnRH并发时接受AI时，在精液加工中掺入CSE往往会改善P / AI。并且使用CSE无法克服预期的授精和排卵之间的异步性。然而，当小母牛在检测到发情或定时AI与5-d CIDR-Synch方案的最终GnRH并发时接受AI时，在精液加工中掺入CSE往往会改善P / AI。而使用CSE无法克服预期的授精和排卵之间的异步性。然而，当小母牛在检测到发情或定时AI与5-d CIDR-Synch协议的最终GnRH并发时接受AI时，在精液加工中掺入CSE往往会改善P / AI。