Souza A H, Ayres H, Ferreira R M, Wiltbank M C
Department of Animal Reproduction, University of São Paulo, São Paulo 05508, Brazil.
Theriogenology. 2008 Jul 15;70(2):208-15. doi: 10.1016/j.theriogenology.2008.03.014. Epub 2008 May 12.
This study evaluated a novel presynchronization method, using Ovsynch prior to the Ovsynch-timed AI protocol (Double-Ovsynch) compared to Presynch-Ovsynch. Lactating Holstein (n=337) cows, were assigned to two treatment groups: (1) Presynch (n=180), two injections of PGF 14 d apart, followed by the Ovsynch-timed AI protocol 12 d later; (2) Double-Ovsynch (n=157), received GnRH, PGF 7 d later, and GnRH 3 d later, followed by the Ovsynch-timed AI protocol 7 d later. All cows received the same Ovsynch-timed AI protocol: GnRH (G1) at 68+/-3 DIM (mean+/-SEM), PGF 7 d later, GnRH (G2) 56h after PGF, and AI 16 to 20h later. Pregnancy was diagnosed 39-45 d after timed AI. Double-Ovsynch increased the pregnancies per AI (P/AI) compared to Presynch-Ovsynch (49.7% vs 41.7%, P=0.03). Surprisingly, Double-Ovsynch increased P/AI only in primiparous (65.2% vs 45.2%; P=0.02) and not multiparous (37.5% vs 39.3%) cows. In a subset of 87 cows, ovarian ultrasonography and progesterone (P4) measurements were performed at G1 and 7 d later. Double-Ovsynch decreased the percentage of cows with low P4 (<1ng/mL) at G1 (9.4% vs 33.3%) and increased the percentage of cows with high P4 (> or =3ng/mL) at PGF (78.1% vs 52.3%). Thus, presynchronization of cows with Double-Ovsynch increased fertility in primiparous cows compared to a standard Presynch protocol, perhaps due to induction of ovulation in non-cycling cows and improved synchronization of cycling cows. Future studies are needed, with a larger number of cows, to further test the hypothesis of higher fertility with Double-Ovsynch, and to elucidate the physiological mechanisms that underlie apparent changes in fertility with this protocol.
本研究评估了一种新型预同步方法，即在Ovsynch定时人工授精方案（双Ovsynch）之前使用Ovsynch，并与预同步-Ovsynch进行比较。将337头泌乳期荷斯坦奶牛分为两个处理组：（1）预同步组（n = 180），间隔14天注射两次PGF，12天后进行Ovsynch定时人工授精方案；（2）双Ovsynch组（n = 157），先注射GnRH，7天后注射PGF，3天后再注射GnRH，7天后进行Ovsynch定时人工授精方案。所有奶牛均接受相同的Ovsynch定时人工授精方案：在68±3天产犊间隔（平均±标准误）时注射GnRH（G1），7天后注射PGF，PGF注射56小时后注射GnRH（G2），16至20小时后进行人工授精。在定时人工授精后39 - 45天诊断妊娠情况。与预同步-Ovsynch相比，双Ovsynch提高了每次人工授精的妊娠率（P/AI）（49.7%对41.7%，P = 0.03）。令人惊讶的是，双Ovsynch仅在初产奶牛中提高了P/AI（65.2%对45.2%；P = 0.02），而经产奶牛中未提高（37.5%对39.3%）。在87头奶牛的子集中，在G1时及7天后进行了卵巢超声检查和孕酮（P4）测量。双Ovsynch降低了G1时孕酮水平低（<1ng/mL）的奶牛百分比（9.4%对33.3%），并提高了PGF时孕酮水平高（≥3ng/mL）的奶牛百分比（78.1%对52.3%）。因此，与标准预同步方案相比，双Ovsynch对奶牛进行预同步提高了初产奶牛的繁殖力，这可能是由于诱导了非周期性奶牛排卵并改善了周期性奶牛的同步性。需要进行更多奶牛参与的未来研究，以进一步验证双Ovsynch具有更高繁殖力的假设，并阐明该方案下繁殖力明显变化背后的生理机制。
