Small J A, Colazo M G, Kastelic J P, Mapletoft R J
Agriculture and Agri-Food Canada, Brandon, Manitoba, Canada R7A 5Y3.
Theriogenology. 2009 Mar 1;71(4):698-706. doi: 10.1016/j.theriogenology.2008.09.045. Epub 2008 Nov 1.
Three experiments were conducted to determine the effects of low-dose progesterone presynchronization and eCG on pregnancy rates to GnRH-based, timed-AI (TAI) in beef cattle (GnRH on Day 0, PGF(2alpha) on Day 7, with GnRH and TAI on Day 9, 54-56 h after PGF(2alpha)). Experiments 1 and 2 were 2 x 2 factorials with presynchronization (with or without a once-used CIDR; Days -15 to 0 in Experiment 1 and Days -7 to 0, with PGF(2alpha) at insertion, in Experiment 2), and with or without 400 IU eCG on Day 7 in suckled cows. In Experiment 3, suckled cows and nulliparous heifers were either presynchronized with a twice-used CIDR (Days -5 to 0) and PGF(2alpha) at insertion, or no treatment prior to insertion of a new CIDR (Days 0-7). Presynchronization increased (P<0.05) ovulation rate to GnRH on Day 0 (75.0% vs 48.7%, 76.7% vs 55.0%, and 60.0% vs 36.1% for Experiments 1, 2, and 3, respectively), increased the diameter of the preovulatory follicle in Experiments 1 and 2, and increased the response to PGF(2alpha) (regardless of parity) in Experiment 1 (P<0.01), and in primiparous cows in Experiment 2 (P<0.01). Effects of presynchronization on pregnancy rates (53.4% vs 54.1%, 57.7% vs 45.3%, and 54.3% vs 44.4% for Experiments 1, 2, and 3, respectively) were influenced by parity and eCG (P<0.05). Treatment with eCG had no effect (P>0.05) on the diameter of the preovulatory follicle (Experiment 1), or the response to PGF(2alpha) (Experiments 1 and 2), but tended (P=0.08) to improve pregnancy rates, especially in primiparous cows that were not presynchronized (P<0.01). However, the effects of eCG and presynchronization were not additive.
进行了三项试验，以确定低剂量孕酮预同步化处理和孕马血清促性腺激素（eCG）对肉牛基于促性腺激素释放激素（GnRH）的定时人工授精（TAI）妊娠率的影响（第0天注射GnRH，第7天注射前列腺素F2α（PGF2α），第9天、PGF2α注射后54 - 56小时注射GnRH并进行TAI）。试验1和试验2采用2×2析因设计，处理因素包括预同步化处理（试验1为第- 15天至第0天使用一次性阴道孕酮释放装置（CIDR），试验2为第- 7天至第0天使用一次性CIDR并在插入时注射PGF2α），以及在第7天对哺乳母牛是否注射400 IU eCG。在试验3中，哺乳母牛和未产青年母牛要么在第- 5天至第0天使用两次性CIDR并在插入时注射PGF2α进行预同步化处理，要么在插入新的CIDR前（第0 - 7天）不进行处理。预同步化处理提高了（P<0.05）第0天对GnRH的排卵率（试验1中分别为75.0%对48.7%，试验2中为76.7%对55.0%，试验3中为60.0%对36.1%），增加了试验1和试验2中排卵前卵泡的直径，并且在试验1中提高了对PGF2α的反应（无论胎次）（P<0.01），在试验2的初产母牛中也提高了对PGF2α的反应（P<0.01）。预同步化处理对妊娠率的影响（试验1中分别为53.4%对54.1%，试验2中为57.7%对45.3%，试验3中为54.3%对44.4%）受胎次和eCG的影响（P<0.05）。eCG处理对排卵前卵泡直径（试验1）或对PGF2α的反应（试验1和试验2）无影响（P>0.05），但有提高妊娠率的趋势（P = 0.08），尤其是在未进行预同步化处理的初产母牛中（P<0.01）。然而，eCG和预同步化处理的效果并非相加。
