Animal Reproduction Laboratory, Texas AgriLife Research, Beeville 78102, USA.
J Anim Sci. 2010 May;88(5):1663-71. doi: 10.2527/jas.2009-2480. Epub 2010 Jan 15.
The objectives were to evaluate the effect of presynchronization with GnRH on pregnancy rates (Exp. 1) and ovarian events (Exp. 2) in Bos indicus-influenced females synchronized with CO-Synch + controlled internal drug release (CIDR) as described below. In Exp. 1, a total of 135 Brahman x Hereford (F(1)) females were assigned randomly after stratification to 1) Presynch; presynchronization followed by CO-Synch + CIDR, or 2) No Presynch; CO-Synch + CIDR without presynchronization. On d -7, cattle received 100 microg of GnRH or 2 mL of intramuscular (i.m.) saline. On d 0, all cattle received a CIDR and i.m. injection of GnRH (GnRH-1), followed by CIDR removal and i.m. injection of 25 mg of PGF(2alpha) (PGF) on d 7, and i.m. injection of GnRH (GnRH-2) and timed AI (TAI) 66 h after CIDR removal (d 10). An additional 77 cows not involved in the Presynch comparison were also treated with CO-Synch + CIDR. Pregnancy rates for Presynch (37.3 +/- 6%) and No Presynch (48.5 +/- 6.1%) did not differ (P = 0.6). Pregnancy rate for all CO-Synch + CIDR-treated cattle combined was 41.9 +/- 6.1 (n = 145). In Exp. 2, we examined ovarian events in 98 Brahman x Hereford (F(1)) cows assigned randomly to Presynch or No Presynch. Ovulatory response to GnRH-1 was greater (P < 0.01) in the Presynch (58 +/- 7.1%) than in the No Presynch (27.1 +/- 6.5%) group. However, emergence of a synchronized new follicular wave after GnRH-1 and ovulation rate after GnRH-2 did not differ between groups (P = 0.4). Presynchronization increased the proportion of females ovulating after GnRH-1, but this did not increase synchrony of new follicular wave emergence or ovulation after GnRH-2, and did not improve TAI pregnancy rates.
目的在于评估 GnRH 同期化处理对妊娠率（试验 1）和卵巢活动（试验 2）的影响，该研究以 Bos indicus 影响的牛为研究对象，使用 CO-Synch+CIDR 进行同期化处理，具体如下。在试验 1 中，总共 135 头 Brahman x Hereford（F(1)）母牛在接受 CO-Synch+CIDR 处理之前根据分层原则被随机分配到以下两组：1）预同期化处理组；2）无预同期化处理组。母牛在第-7 天注射 100µg GnRH 或 2ml 肌内注射生理盐水。第 0 天，所有母牛均放置 CIDR 并肌内注射 GnRH（GnRH-1），第 7 天，取出 CIDR 并肌内注射 25mgPGF2α（PGF），第 10 天，肌内注射 GnRH（GnRH-2）并在 CIDR 取出后 66 小时输精（第 10 天）。另外，77 头未参与预同期化处理比较的母牛也接受了 CO-Synch+CIDR 处理。预同期化处理组的妊娠率（37.3±6%）和无预同期化处理组（48.5±6.1%）无显著差异（P=0.6）。接受 CO-Synch+CIDR 处理的母牛妊娠率为 41.9±6.1%（n=145）。在试验 2 中，我们随机分配 98 头 Brahman x Hereford（F(1)）母牛到预同期化处理组或无预同期化处理组。GnRH-1 的排卵反应在预同期化处理组（58±7.1%）比无预同期化处理组（27.1±6.5%）更高（P<0.01）。然而，GnRH-1 后新卵泡波的同步出现和 GnRH-2 后的排卵率在两组之间没有差异（P=0.4）。预同期化处理增加了 GnRH-1 后排卵的母牛比例，但这并没有增加 GnRH-2 后新卵泡波出现或排卵的同步性，也没有提高 TAI 妊娠率。
