Department of Animal Science, Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo, Piracicaba, SP, 13418-900, Brazil; Department of Animal and Dairy Science, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Department of Animal Science, Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo, Piracicaba, SP, 13418-900, Brazil.
Theriogenology. 2020 Mar 15;145:126-137. doi: 10.1016/j.theriogenology.2020.01.030. Epub 2020 Jan 16.
Three experiments evaluated ovarian dynamics and circulating progesterone (P4) during P4-based protocols initiated with GnRH, estradiol benzoate (EB), or no additional treatment in Nelore (Bos indicus) cattle. In Exp 1 (n = 59 cows), a 5-d P4-only protocol (P-5d; D0: P4 implant alone (1g); D5: P4 removal, 0.5 mg estradiol cypionate [EC], 0.526 mg cloprostenol [PGF], and 300 IU equine chorionic gonadotropin [eCG]; D7: 8.4 μg buserelin acetate [GnRH]) was compared to a 9d protocol initiated with EB (EB-9d; D0: 2 mg EB + P4; D9: P4 removal + EC + PGF + eCG), and to a 7d GnRH protocol (G-7d; D0: 16.8 μg GnRH + P4; D6: PGF + eCG; D7: P4 removal + PGF; D9: GnRH). Exp 2 (n = 55 cows) compared G-7d and EB-7d protocols (similar to EB-9d, but D9 treatments were done on D7). Exp 3 (n = 64 heifers) compared EB-7d, G-7d, and P-5d protocols. For all experiments, daily ovarian ultrasonography was done from D0 until 4d after implant withdrawal and blood samples were collected at D0 and first PGF. Follicle dynamics were determined for each individual animal, analyzed within individual experiments, and afterwards combined to determine overall effects of treatments. The protocol that began with GnRH, G-7d, had greater ovulation rate after D0 with subsequently greater number of CL and circulating P4 at time of PGF (52.8%, 1.0 ± 0.1 CL, 4.0 ± 0.4 ng/mL) than for EB protocols (12.1%, 0.4 ± 0.05 CL, 2.0 ± 0.2 ng/mL), or P-5d (2.5%, 0.6 ± 0.09 CL, 2.6 ± 0.3 ng/mL). The G-7d and EB protocols had synchronized follicle wave emergence in 92.1% of animals but with distinct patterns. For the G-7d group, wave emergence occurred earlier in ovulating than non-ovulating animals (1.4 ± 0.2 d vs 2.5 ± 0.4 d). By comparison, most animals in EB-7d or EB-9d (80.3%) displayed atresia of the dominant follicle, followed by wave emergence 2-3 d after EB treatment. In contrast, P-5d protocol synchronized wave emergence in only 30.0% of cows. Nevertheless, no differences among treatments were detected for ovulation at end of the protocol (85.7%). In conclusion, the P-5d protocol did not synchronize follicle wave emergence but produced similar final ovulation, whereas, GnRH and EB protocols had follicle dynamics synchronized by distinct mechanisms that produced differences in CL number and P4 at the time of PGF treatment but similar final ovulation. Based on ovarian function, each of these synchronization methods are promising for use in FTAI, although fertility still needs to be evaluated.
三个实验评估了 GnRH、苯甲酸雌二醇 (EB) 或不额外治疗在尼洛牛（Bos indicus）中启动的基于孕激素的方案中卵巢动态和循环孕激素 (P4)。在实验 1（n = 59 头奶牛）中，进行了为期 5 天的孕激素方案（P-5d；D0：单独孕激素植入 1g；D5：孕激素去除，0.5mg 戊酸雌二醇 [EC]、0.526mg 氯前列醇 [PGF] 和 300IU 马绒毛膜促性腺激素 [eCG]；D7：8.4μg 布舍瑞林乙酸盐 [GnRH]）与 EB 启动的 9 天方案（EB-9d；D0：2mg EB + P4；D9：孕激素去除 + EC + PGF + eCG）和 7 天 GnRH 方案（G-7d；D0：16.8μg GnRH + P4；D6：PGF + eCG；D7：孕激素去除 + PGF；D9：GnRH）进行比较。实验 2（n = 55 头奶牛）比较了 G-7d 和 EB-7d 方案（与 EB-9d 相似，但 D9 治疗在 D7 进行）。实验 3（n = 64 头小母牛）比较了 EB-7d、G-7d 和 P-5d 方案。对于所有实验，从 D0 到植入物取出后 4 天，每天对卵巢进行超声检查，并在 D0 和第一次 PGF 时采集血液样本。确定了每个个体动物的卵泡动态，在个体实验中进行了分析，然后结合起来确定处理的总体效果。以 GnRH 开始的方案，G-7d，在 D0 后排卵率更高，随后在 PGF 时的 CL 和循环 P4 数量更多（52.8%，1.0 ± 0.1 CL，4.0 ± 0.4ng/mL）比 EB 方案（12.1%，0.4 ± 0.05 CL，2.0 ± 0.2ng/mL）或 P-5d（2.5%，0.6 ± 0.09 CL，2.6 ± 0.3ng/mL）。G-7d 和 EB 方案有 92.1%的动物同步卵泡波出现，但模式不同。对于 G-7d 组，排卵动物的波出现时间早于不排卵动物（1.4 ± 0.2d 对 2.5 ± 0.4d）。相比之下，EB-7d 或 EB-9d 组的大多数动物（80.3%）表现出优势卵泡闭锁，然后在 EB 治疗后 2-3 天出现波出现。相比之下，P-5d 方案仅在 30.0%的奶牛中同步波出现。然而，在方案结束时，治疗之间在排卵方面没有差异（85.7%）。总之，P-5d 方案未能同步卵泡波出现，但产生了相似的最终排卵，而 GnRH 和 EB 方案通过不同的机制同步卵泡动态，在 PGF 治疗时产生了 CL 数量和 P4 的差异，但最终排卵相似。基于卵巢功能，这些同步方法中的每一种都有望用于 FTAI，尽管仍需要评估生育能力。
