USDA, ARS, US Meat Animal Research Center, Clay Center, NE 68933-0166, USA.
J Anim Sci. 2011 Oct;89(10):3060-8. doi: 10.2527/jas.2010-3549. Epub 2011 May 6.
Application of AI in extensive beef cattle production would be facilitated by protocols that effectively synchronize ovarian follicular development and ovulation to enable fixed-time AI (TAI). The objectives were to determine whether use of a controlled internal drug release (CIDR) device to administer progesterone in a GnRH-based estrous synchronization protocol would optimize blood progesterone concentrations, improve synchronization of follicular development and estrus, and increase pregnancy rates to TAI in beef cows. Beef cows (n = 1,240) in 6 locations within the US Meat Animal Research Center received 1 of 2 treatments: 1) an injection of GnRH [100 µg intramuscularly (i.m.)] followed by PGF(2α) (PGF; 25 mg i.m.) 7 d later (CO-Synch), or 2) CO-Synch plus a CIDR during the 7 d between GnRH and PGF injections (CO-Synch + CIDR). Cows received TAI and GnRH (100 µg i.m.) at 60 h after PGF. Progesterone was measured by RIA in blood samples collected 2 wk before and at initiation of treatment (d 0) and at PGF injection (d 7). Estrous behavior was monitored by Estrotect Heat Detectors. Pregnancy was diagnosed by ultrasonography 72 to 77 d after TAI. Plasma progesterone concentrations did not differ (P > 0.10) between synchronization protocols at first GnRH injection (d 0), but progesterone was greater (P < 0.01) at PGF injection (d 7) in cows receiving CO-Synch + CIDR vs. CO-Synch as a result of fewer CIDR-treated cows having progesterone ≤1 ng/mL at PGF (10.7 vs. 29.6%, respectively). A greater (P < 0.01) proportion of CO-Synch + CIDR vs. CO-Synch cows were detected in estrus within 60 h after PGF (66.7 vs. 57.8 ± 2.6%, respectively) and a greater (P < 0.01) proportion were pregnant to TAI (54.6 vs. 44.3 ± 2.6%, respectively). For both synchronization protocols, cows expressing estrus within 60 h before TAI had a greater pregnancy rate than cows without estrus. For cows with plasma progesterone ≤1 ng/mL at PGF injection, CO-Synch + CIDR increased pregnancy rate (65.2 ± 5.9 vs. 30.8 ± 3.4% with vs. without CIDR), whereas pregnancy rates did not differ (P > 0.10) between protocols (52.1 ± 2.1 vs. 50.0 ± 2.4%, respectively) when progesterone was >1 ng/mL (treatment × progesterone; P < 0.01). Inclusion of a CIDR in the synchronization protocol increased plasma progesterone concentration, proportion of cows detected in estrus, and pregnancy rate; however, the increase in pregnancy rate from inclusion of the CIDR was primarily in cows with decreasing or low endogenous progesterone secretion during treatment.
人工智能在广泛的肉牛生产中的应用将得益于能够有效同步卵巢卵泡发育和排卵以实现定时人工授精（TAI）的方案。目的是确定在基于 GnRH 的发情同步方案中使用控释宫内节育器（CIDR）给药来施用孕酮是否会优化血液孕酮浓度，改善卵泡发育和发情同步，并提高 TAI 时的妊娠率。在美国肉类动物研究中心内的 6 个地点的 1240 头肉牛接受了以下 2 种处理之一：1）肌肉注射 GnRH[100μg（肌肉注射）]，然后在第 7 天注射 PGF（2α）（PGF；25mg 肌肉注射）（CO-Synch），或 2）在 GnRH 和 PGF 注射之间的 7 天内 CO-Synch 加 CIDR（CO-Synch + CIDR）。在 PGF 注射后 60 小时，牛接受 TAI 和 GnRH（100μg 肌肉注射）。在 2 周前和治疗开始时（第 0 天）以及 PGF 注射时（第 7 天）通过 RIA 测量孕酮。通过 Estrotect 热探测器监测发情行为。在 TAI 后 72 至 77 天通过超声诊断妊娠。第一次 GnRH 注射时（第 0 天），两个同步方案的血浆孕酮浓度没有差异（P>0.10），但由于接受 CO-Synch + CIDR 的牛中孕酮≤1ng/mL 的 CIDR 治疗牛在 PGF 时的孕酮更少（分别为 10.7%和 29.6%），PGF 注射时（第 7 天）孕酮更高（P<0.01）。与 CO-Synch 相比，接受 CO-Synch + CIDR 的牛在 PGF 后 60 小时内发情的比例更高（分别为 66.7%和 57.8±2.6%），并且发情的比例更高（P<0.01）TAI 时怀孕（分别为 54.6%和 44.3±2.6%）。对于这两个同步方案，在 TAI 前 60 小时内表现发情的牛比没有发情的牛的妊娠率更高。对于 PGF 注射时孕酮≤1ng/mL 的牛，CO-Synch + CIDR 增加了妊娠率（分别为 65.2±5.9%和 30.8±3.4%），而当孕酮大于 1ng/mL 时（治疗×孕酮；P<0.01），妊娠率没有差异（P>0.10）（分别为 52.1±2.1%和 50.0±2.4%）。在同步方案中加入 CIDR 会增加血浆孕酮浓度、发情牛的比例和妊娠率；然而，CIDR 增加的妊娠率主要来自于治疗期间孕酮分泌减少或低的牛。
