Department of Dairy Science, University of Wisconsin, Madison 53706, USA.
J Dairy Sci. 2012 Feb;95(2):639-53. doi: 10.3168/jds.2011-4418.
The objective was to determine if using a Double-Ovsynch protocol [DO; Pre-Resynch: GnRH-7 d-PGF(2α)-3 d-GnRH, 7 d later Breeding-Resynch: GnRH-7 d-PGF(2α)-56 h-GnRH-16 h-timed artificial insemination (TAI)] to resynchronize ovulation after a previous TAI would increase synchrony and pregnancies per AI (P/AI) compared with an Ovsynch protocol initiated 32 d after TAI (D32; GnRH-7 d-PGF(2α)-56 h-GnRH-16 h-TAI). Lactating Holstein cows at various days in milk and prior AI services were blocked by parity and randomly assigned to resynchronization treatments. All DO cows received the first GnRH injection of Pre-Resynch 22 d after TAI, and cows (n=981) diagnosed not pregnant using transrectal ultrasonography 29 d after TAI continued the protocol. Pregnancy status for all D32 cows was evaluated 29 d after TAI so fertility and pregnancy loss could be compared with that of DO cows. All D32 cows received the first GnRH injection of Ovsynch 32 d after TAI, and cows (n=956) diagnosed not pregnant using transrectal palpation 39 d after TAI continued the protocol. In a subgroup of cows from each treatment, ultrasonography (n=751) and serum progesterone (P4) concentrations (n=743) were used to determine the presence of a functional corpus luteum (CL) and ovulation to the first GnRH injection of D32 and Breeding-Resynch of DO (GnRH1), luteal regression after PGF before TAI, and ovulation to the GnRH injection before TAI (GnRH2). Overall, P/AI 29 d after TAI was not affected by parity and was greater for DO compared with D32 cows (39 vs. 30%). Pregnancy loss from 29 to 74 d after TAI was not affected by parity or treatment. The percentage of cows with a functional CL (P4 ≥1.0 ng/mL) at GnRH1 was greater for DO than D32 cows (81 vs. 58%), with most DO cows having medium P4 (60%; 1.0 to 3.49 ng/ml), whereas most D32 cows had either low (42%; <1.0 ng/mL) or high (36%; ≥3.5 ng/mL) P4 at GnRH1. Ovulation to GnRH1 was similar between treatments but was affected by serum P4 at GnRH. Cows with low P4 (<1.0 ng/mL) had the greatest ovulatory response (59%), followed by cows with medium (≥1.0 to 3.49 ng/mL; 38%) and then high (≥3.50 ng/mL; 16%) P4 at GnRH1. A greater percentage of DO cows were synchronized compared with D32 cows (72 vs. 51%) primarily due to a greater percentage of D32 than DO cows without a functional CL at the PGF injection before TAI (35 vs. 17%) or without complete CL regression before GnRH2 (17 vs. 7%). We conclude that DO increased fertility of lactating dairy cows during a resynchronization program primarily by increasing synchronization of cows during the Ovsynch protocol before TAI.
目的是确定在之前的人工授精（TAI）后使用双发情同期化方案[DO；预同期化：GnRH-7 d-PGF（2α）-3 d-GnRH，7 d 后发情同期化：GnRH-7 d-PGF（2α）-56 h-GnRH-16 h 定时人工授精（TAI）]重新同期发情是否会增加同步发情和每人工授精受胎率（P/AI），与发情同期化方案 32 d 后（D32；GnRH-7 d-PGF（2α）-56 h-GnRH-16 h-TAI）启动的方案相比。处于不同泌乳天数和之前进行过人工授精服务的泌乳荷斯坦奶牛根据胎次进行分组，并随机分配到同期发情处理组。所有 DO 奶牛在 TAI 后 22 d 接受了 Pre-Resynch 的第一次 GnRH 注射，在 TAI 后 29 d 通过直肠超声检查诊断未怀孕的奶牛继续进行该方案。所有 D32 奶牛在 TAI 后 29 d 评估怀孕情况，以便将其繁殖力和妊娠损失与 DO 奶牛进行比较。所有 D32 奶牛在 TAI 后 32 d 接受了第一次 GnRH 注射的 Ovsynch，在 TAI 后 39 d 通过直肠触诊诊断未怀孕的奶牛继续进行该方案。在每个处理组的奶牛亚组中，使用超声检查（n=751）和血清孕酮（P4）浓度（n=743）来确定是否存在功能性黄体（CL）和排卵到 D32 的第一次 GnRH 注射和 DO 的发情同期化（GnRH1），在 TAI 前 PGF 引起的黄体退化和 TAI 前 GnRH2 引起的排卵。总体而言，TAI 后 29 d 的 P/AI 不受胎次影响，DO 奶牛的 P/AI 高于 D32 奶牛（39 对 30%）。TAI 后 29 至 74 d 的妊娠损失不受胎次或处理的影响。在 GnRH1 时具有功能性 CL（P4≥1.0 ng/mL）的奶牛百分比 DO 奶牛高于 D32 奶牛（81%对 58%），大多数 DO 奶牛的 P4 处于中等水平（60%；1.0 至 3.49 ng/ml），而大多数 D32 奶牛的 P4 要么较低（42%；<1.0 ng/mL），要么较高（36%；≥3.5 ng/mL）。排卵到 GnRH1 在两种处理之间相似，但受 GnRH 时的血清 P4 影响。P4 较低（<1.0 ng/mL）的奶牛排卵反应最大（59%），其次是 P4 中等（≥1.0 至 3.49 ng/mL；38%），然后是 P4 较高（≥3.50 ng/mL；16%）。与 D32 奶牛相比，更多的 DO 奶牛同步发情（72%对 51%），主要是由于在 TAI 前的 PGF 注射时没有功能性 CL（35%对 17%）或在 GnRH2 前没有完全的黄体退化（17%对 7%）的 D32 奶牛比例较高。我们得出结论，DO 通过在 TAI 前发情同期化方案中增加奶牛同期发情的比例，主要增加了哺乳期奶牛同期发情方案的繁殖力。
