Departamento de Reprodução Animal, FMVZ-USP, São Paulo-SP, Brazil.
Theriogenology. 2010 Mar 15;73(5):651-8. doi: 10.1016/j.theriogenology.2009.11.004. Epub 2010 Jan 18.
Two experiments were conducted to investigate the effects of equine chorionic gonadotropin (eCG) at progestin removal and gonadotropin-releasing hormone (GnRH) at timed artificial insemination (TAI) on ovarian follicular dynamics (Experiment 1) and pregnancy rates (Experiment 2) in suckled Nelore (Bos indicus) cows. Both experiments were 2x2 factorials (eCG or No eCG, and GnRH or No GnRH), with identical treatments. In Experiment 1, 50 anestrous cows, 134.5+/-2.3 d postpartum, received a 3mg norgestomet ear implant sc, plus 3mg norgestomet and 5mg estradiol valerate im on Day 0. The implant was removed on Day 9, with TAI 54 h later. Cows received 400 IU eCG or no further treatment on Day 9 and GnRH (100 microg gonadorelin) or no further treatment at TAI. Treatment with eCG increased the growth rate of the largest follicle from Days 9 to 11 (means+/-SEM, 1.53+/-0.1 vs. 0.48+/-0.1mm/d; P<0.0001), its diameter on Day 11 (11.4+/-0.6 vs. 9.3+/-0.7 mm; P=0.03), as well as ovulation rate (80.8% vs. 50.0%, P=0.02), whereas GnRH improved the synchrony of ovulation (72.0+/-1.1 vs. 71.1+/-2.0 h). In Experiment 2 (n=599 cows, 40 to 120 d postpartum), pregnancy rates differed (P=0.004) among groups (27.6%, 40.1%, 47.7%, and 55.7% for Control, GnRH, eCG, and eCG+GnRH groups). Both eCG and GnRH improved pregnancy rates (51.7% vs. 33.8%, P=0.002; and 48.0% vs 37.6%, P=0.02, respectively), although their effects were not additive (no significant interaction). In conclusion, eCG at norgestomet implant removal increased the growth rate of the largest follicle (LF) from implant removal to TAI, the diameter of the LF at TAI, and rates of ovulation and pregnancy rates. Furthermore, GnRH at TAI improved the synchrony of ovulations and pregnancy rates in postpartum Nelore cows treated with a norgestomet-based TAI protocol.
进行了两项实验来研究在孕激素去除时使用马绒毛膜促性腺激素（eCG）和在定时人工授精（TAI）时使用促性腺激素释放激素（GnRH）对哺乳期内（Bos indicus）Nelore 奶牛的卵巢卵泡动态（实验 1）和妊娠率（实验 2）的影响。这两个实验都是 2x2 析因设计（eCG 或无 eCG，和 GnRH 或无 GnRH），使用相同的处理方法。在实验 1 中，50 头乏情奶牛，产后 134.5+/-2.3 天，接受了 sc 3mg 去氧孕烯庚酸酯耳埋植剂，外加 3mg 去氧孕烯庚酸酯和 5mg 戊酸雌二醇 im，于第 0 天。植入物于第 9 天取出，54 小时后进行 TAI。第 9 天，奶牛接受了 400IU eCG 或无进一步处理，以及 GnRH（100μg 戈那瑞林）或 TAI 时无进一步处理。eCG 的处理增加了从第 9 天到第 11 天的最大卵泡的生长速度（平均值+/-SEM，1.53+/-0.1 对 0.48+/-0.1mm/d；P<0.0001），第 11 天的直径（11.4+/-0.6 对 9.3+/-0.7mm；P=0.03），以及排卵率（80.8%对 50.0%，P=0.02），而 GnRH 提高了排卵的同步性（72.0+/-1.1 对 71.1+/-2.0 小时）。在实验 2（n=599 头奶牛，产后 40 至 120 天）中，各组之间的妊娠率不同（P=0.004）（对照组、GnRH 组、eCG 组和 eCG+GnRH 组分别为 27.6%、40.1%、47.7%和 55.7%）。eCG 和 GnRH 都提高了妊娠率（51.7%对 33.8%，P=0.002；和 48.0%对 37.6%，P=0.02，分别），尽管它们的作用不是相加的（无显著的交互作用）。总之，在使用基于去氧孕烯庚酸酯的 TAI 方案治疗的 Nelore 产后奶牛中，在孕激素去除时使用 eCG 增加了从植入物去除到 TAI 的最大卵泡（LF）的生长速度、TAI 时 LF 的直径、排卵率和妊娠率。此外，在 TAI 时使用 GnRH 提高了排卵的同步性和妊娠率。
