Department of Animal Science, Cornell University, Ithaca, NY 14853.
Department of Animal Science, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 2022 Oct;105(10):8411-8425. doi: 10.3168/jds.2022-22082. Epub 2022 Aug 24.
The primary objective of this randomized controlled experiment was to evaluate the insemination dynamic and reproductive performance of cows managed with a targeted reproductive management (TRM) program designed to prioritize artificial insemination (AI) at detected estrus (AIE) and optimize timing of AI by grouping cows based on detection of estrus during the voluntary waiting period (VWP). Our secondary objective was to evaluate reproductive outcomes for cows with or without estrus during the VWP. Lactating Holstein cows fitted with an ear-attached sensor for detection of estrus were randomly assigned to a TRM treatment that prioritized AIE based on detection of estrus during the VWP (TP-AIE; n = 488), a non-TRM treatment that prioritized AIE (P-AIE; n = 489), or an all timed AI (TAI) treatment with extended VWP (ALL-TAI; n = 491). In TP-AIE, cows with or without automated estrus alerts (AEA) recorded during the VWP received AIE if detected in estrus for at least 31 ± 3 or 17 ± 3 d after a 49 d VWP, respectively. Cows not AIE with or without AEA during the VWP received TAI after Ovsynch with progesterone supplementation and 2 PGF treatments (P4-Ov) at 90 ± 3 or 74 ± 3 d in milk (DIM), respectively. In P-AIE, cows received AIE if detected in estrus for 24 ± 3 d after a 49 d VWP, and if not AIE received TAI at 83 ± 3 DIM after P4-Ov. In ALL-TAI, cows received TAI at 83 ± 3 DIM after a Double-Ovsynch protocol. Data were analyzed by logistic and Cox's proportional hazard regression. The proportion of cows AIE did not differ for TP-AIE (71.0%) and P-AIE (74.6%). Overall P/AI at 39 d after first service was greater for the ALL-TAI (47.6%) than for the P-AIE (40.2%) and TP-AIE (39.5%) treatments. The hazard of pregnancy up to 150 DIM was greater for cows in TP-AIE (hazard ratio = 1.2; 95% confidence interval: 1.1-1.4) and P-AIE (hazard ratio = 1.2; 95% confidence interval: 1.1-1.4) than for cows in the ALL-TAI treatment which resulted in median time to pregnancy of 89, 89, and 107 d. Conversely, the proportion of cows pregnant at 150 DIM did not differ (ALL-TAI 78.5%, P-AIE 76.3%, TP-AIE 76.0%). Except for a few outcomes for which no difference was observed, cows detected in estrus during the VWP had better performance than cows not detected in estrus. Cows with AEA during the VWP were more likely to receive AIE, had greater P/AI, and greater pregnancy rate up to 150 DIM regardless of first service management. We conclude that a TRM program designed to prioritize AIE by grouping cows based on detection of estrus during the VWP was an effective strategy to submit cows for first service resulting in similar or improved performance than a non-TRM program that prioritized AIE or an all-TAI program with extended VWP. Also, AEA recorded during the VWP might be used as a strategy for identifying subgroups of cows with different reproductive performance.
本随机对照试验的主要目的是评估在目标繁殖管理（TRM）方案管理下的奶牛的授精动态和繁殖性能，该方案旨在通过在自愿等待期（VWP）内根据发情检测将奶牛分组，来优先进行人工授精（AI）并优化 AI 时间，以检测发情（AIE）。我们的次要目标是评估 VWP 期间有或没有发情的奶牛的繁殖结果。佩戴用于检测发情的耳夹传感器的泌乳荷斯坦奶牛被随机分配到 TRM 处理组，该处理组基于 VWP 期间的发情检测（TP-AIE；n = 488），非 TRM 处理组（P-AIE；n = 489），或在 VWP 延长时进行的所有定时 AI（TAI）处理（ALL-TAI；n = 491）。在 TP-AIE 中，VWP 期间有或没有自动发情警报（AEA）记录的奶牛，如果在发情后至少 31 ± 3 或 17 ± 3 天进行 AIE，则接受 AIE。VWP 期间没有发情且没有 AEA 的奶牛，如果在发情后至少 31 ± 3 或 17 ± 3 天进行 AIE，则接受 AIE。VWP 期间没有发情且没有 AEA 的奶牛在 Ovsynch 后接受孕激素补充和 2 次 PGF 治疗（P4-Ov），分别在产奶后 90 ± 3 或 74 ± 3 天（DIM）。在 P-AIE 中，奶牛如果在 VWP 后 24 ± 3 天发情，则接受 AIE，如果未发情，则在 P4-Ov 后 83 ± 3 DIM 接受 TAI。在 ALL-TAI 中，奶牛在双 Ovsynch 方案后 83 ± 3 DIM 接受 TAI。数据通过逻辑和 Cox 比例风险回归进行分析。TP-AIE（71.0%）和 P-AIE（74.6%）的发情奶牛比例没有差异。首次配种后 39 天的总配种率（P/AI）在 ALL-TAI（47.6%）中高于 P-AIE（40.2%）和 TP-AIE（39.5%）。直至 150 DIM 的妊娠风险在 TP-AIE（危险比 = 1.2；95%置信区间：1.1-1.4）和 P-AIE（危险比 = 1.2；95%置信区间：1.1-1.4）中更高，而在 ALL-TAI 处理中，妊娠时间中位数为 89、89 和 107 d。相反，150 DIM 时怀孕的奶牛比例没有差异（ALL-TAI 78.5%，P-AIE 76.3%，TP-AIE 76.0%）。除了少数观察到没有差异的结果外，在 VWP 期间检测到发情的奶牛比未检测到发情的奶牛表现更好。在 VWP 期间有 AEA 的奶牛更有可能接受 AIE，具有更高的 P/AI 和更高的妊娠率，直至 150 DIM，无论第一服务管理如何。我们得出结论，设计旨在通过在 VWP 期间根据发情检测将奶牛分组来优先进行 AIE 的 TRM 方案是一种有效的策略，可以提交奶牛进行首次服务，从而产生与优先进行 AIE 或 VWP 延长的所有定时 AI 方案相似或改善的性能。此外，在 VWP 期间记录的 AEA 可能被用作识别具有不同繁殖性能的奶牛亚群的策略。
