Division of Animal Sciences, University of Missouri, Columbia, MO, 65211, USA; College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA.
Cross Country Genetics, Westmoreland, KS, 66549, USA.
Theriogenology. 2020 Dec;158:490-496. doi: 10.1016/j.theriogenology.2020.09.033. Epub 2020 Sep 28.
An experiment was designed to evaluate the effectiveness of the recently developed 7 & 7 Synch protocol to synchronize estrus among recipients prior to embryo transfer (ET). Postpartum beef cows (n = 1358) across thirteen locations were assigned to either the 7-d CO-Synch + CIDR protocol or the 7 & 7 Synch protocol prior to ET. Cows were preassigned to balanced treatments within location based on age and days postpartum, with body condition score recorded at ET. Cows assigned to the 7-d CO-Synch + CIDR protocol were administered gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin acetate) on Day 7, an intravaginal controlled internal drug release (CIDR; 1.38 g progesterone) from Day 7 to Day 14, and prostaglandin F (PGF; 25 mg dinoprost tromethamine) coincident with CIDR removal on Day 14. Cows assigned to the 7 & 7 Synch protocol were administered PGF (25 mg dinoprost tromethamine) coincident with CIDR insertion on Day 0, GnRH (100 μg gonadorelin acetate) on Day 7, and PGF (25 mg dinoprost tromethamine) coincident with CIDR removal on Day 14. Cows were observed for visible signs of estrus, with GnRH (100 μg gonadorelin acetate) administered to cows failing to express estrus during the detection period. Embryo transfer was performed approximately seven days after estrus or GnRH administration. Presence of corpora lutea (CL) was determined via transrectal palpation by a single veterinarian blinded to treatment, and embryos were transferred only to cows with palpable CL. Embryo transfer was performed using either fresh or frozen embryos, with embryo stage and grade recorded for each recipient. The proportion of cows expressing estrus was increased (P < 0.0001) among cows assigned to the 7 & 7 Synch protocol (86% [529/615] vs 76% [488/640]). The proportion of cows expressing estrus and presenting with palpable CL at ET was greater (P < 0.0001) among cows following treatment with the 7 & 7 Synch protocol compared to the 7-d CO-Synch + CIDR protocol (76% [466/615] vs 65% [418/640]). Consequently, the proportion pregnant to ET was greater (P < 0.03) following the 7 & 7 Synch protocol (40% [263/653]) compared to the 7-d CO-Synch + CIDR protocol (34% [228/664]). In summary, the 7 & 7 Synch protocol involving administration of PGF and treatment with a CIDR for 7 days prior to GnRH improved the likelihood of estrus expression in recipients, increased the proportion of cows eligible to receive an embryo, which resulted in a greater pregnancy rate to ET.
设计了一项实验，以评估最近开发的 7 & 7 Synch 方案在胚胎移植 (ET) 前同步受体发情的效果。在 13 个地点的产后肉牛（n=1358）被分配到 7-d CO-Synch + CIDR 方案或 7 & 7 Synch 方案，然后进行 ET。根据年龄和产后天数，在每个地点内将牛预先分配到平衡处理中，并在 ET 时记录体况评分。被分配到 7-d CO-Synch + CIDR 方案的牛在第 7 天接受促性腺激素释放激素 (GnRH；100μg 戈那瑞林乙酸)，第 7 天至第 14 天阴道内给予受控内部药物释放 (CIDR；1.38g 孕酮)，第 14 天与 CIDR 去除时给予前列腺素 F (PGF；25mg 二氮丙嗪三甲胺)。被分配到 7 & 7 Synch 方案的牛在第 0 天插入 CIDR 时接受 PGF（25mg 二氮丙嗪三甲胺），第 7 天接受 GnRH（100μg 戈那瑞林乙酸），第 14 天与 CIDR 去除时接受 PGF（25mg 二氮丙嗪三甲胺）。观察牛是否出现发情迹象，对发情检测期间未表现发情的牛注射 GnRH（100μg 戈那瑞林乙酸）。发情或 GnRH 给药后大约 7 天进行胚胎移植。通过直肠触诊由一名对治疗不知情的单一兽医确定黄体 (CL) 的存在，并仅将胚胎转移到可触及 CL 的牛。胚胎移植使用新鲜或冷冻胚胎进行，每个受体都记录胚胎的阶段和等级。与接受 7-d CO-Synch + CIDR 方案的牛相比，被分配到 7 & 7 Synch 方案的牛发情比例增加（P<0.0001）（86% [529/615] vs 76% [488/640]）。与接受 7-d CO-Synch + CIDR 方案的牛相比，接受 7 & 7 Synch 方案治疗的牛发情且 ET 时可触及 CL 的比例更高（P<0.0001）（76% [466/615] vs 65% [418/640]）。因此，与接受 7-d CO-Synch + CIDR 方案相比（40% [263/653]），接受 7 & 7 Synch 方案的牛怀孕至 ET 的比例更高（P<0.03）（40% [263/653]）。总之，PGF 给药和 GnRH 前 7 天使用 CIDR 的 7 & 7 Synch 方案提高了受体发情表达的可能性，增加了有资格接受胚胎的牛的比例，从而提高了 ET 的妊娠率。
