Department of Animal Science, Texas A&M University,College Station, TX77845, USA.
School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18168-000, Brazil.
Animal. 2019 Nov;13(11):2569-2575. doi: 10.1017/S1751731119000636. Epub 2019 Apr 10.
Expression of estrus (EST) near the time of fixed-time artificial insemination (FTAI) increases pregnancy success in beef females. This outcome has been associated with improved pregnancy establishment and maintenance, although research is still warranted to validate this theory. Hence, this experiment compared ovarian, uterine and conceptus factors associated with pregnancy establishment in Bos indicus beef cows according to estrous expression during a FTAI protocol. One hundred lactating multiparous Nelore cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device on day -11, a 12.5 mg injection of prostaglandin F2α on day -4, P4 device removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of equine chorionic gonadotropin on day -2, and FTAI on day 0. An estrous detection patch was attached to the tailhead of each cow on day -2, and estrous expression was defined as removal of >50% of the rub-off coating from the patch at FTAI. Overall, 39 cows expressed EST, 55 did not express EST (NOEST), and six cows lost their patch and were discarded from the experiment. Ovarian ultrasonography was performed at FTAI, and on days 7 and 15 of the experiment. Blood samples were also collected on days 7 and 15. Only cows without a corpus luteum (CL) on day 0, and with a CL on days 7 and 15 remained in the experiment (EST, n=36; NOEST, n=48). On day 15, cows were randomly selected within each group (EST, n=29; NOEST, n=30) for conceptus collection via transcervical flushing, followed by endometrial biopsy in the uterine horn ipsilateral to the CL. Within cows not assigned to conceptus collection, blood samples were collected for whole blood RNA extraction (day 20) and pregnancy status was verified by transrectal ultrasonography (day 30). Diameter of dominant follicle on day 0 and plasma P4 concentrations on day 7 were greater (P⩽0.02) in EST v. NOEST cows. Conceptus length and messenger RNA (mRNA) expression of prostaglandin E synthase and interferon-tau were greater (P⩽0.04) in EST v. NOEST cows. Moreover, EST cows diagnosed as pregnant on day 30 had greater (P<0.01) blood mRNA expression of myxovirus resistance 2 on day 20 compared with NOEST. In summary, estrous expression near the time of FTAI enhanced pregnancy establishment factors in B. indicus cows, including conceptus development and mRNA expression of interferon-tau.
发情表达（EST）接近定时人工授精（FTAI）的时间可以提高肉牛雌性的妊娠成功率。这一结果与改善妊娠建立和维持有关，尽管仍需要研究来验证这一理论。因此，本实验比较了根据 FTAI 方案发情表达的印度瘤牛肉牛的卵巢、子宫和胚胎因素与妊娠建立的关系。100 头泌乳经产尼洛牛在-11 天接受 2 毫克苯甲酸雌二醇注射和阴道内孕酮（P4）释放装置，-4 天接受 12.5 毫克前列腺素 F2α 注射，-2 天除了 P4 装置去除外，还接受 0.6 毫克雌二醇环戊丙酸酯和 300 国际单位马绒毛膜促性腺激素注射，0 天进行 FTAI。在-2 天，将发情检测贴片贴在每头牛的尾头上，发情表达定义为在 FTAI 时贴片的脱落涂层去除超过 50%。总的来说，有 39 头牛表现出 EST，55 头牛没有表现出 EST（NOEST），6 头牛失去贴片并被从实验中淘汰。在 FTAI 时以及实验的第 7 天和第 15 天进行卵巢超声检查。还在第 7 天和第 15 天采集血样。仅在第 0 天没有黄体（CL），并且在第 7 天和第 15 天有 CL 的牛仍留在实验中（EST，n=36；NOEST，n=48）。在第 15 天，在每个组内随机选择牛（EST，n=29；NOEST，n=30）进行经宫颈冲洗以收集胚胎，然后在与 CL 同侧的子宫角进行子宫内膜活检。在未分配进行胚胎收集的牛中，在第 20 天采集血液样本进行全血 RNA 提取，并在第 30 天通过直肠超声检查验证妊娠状态。在 EST 牛中，第 0 天的主导卵泡直径和第 7 天的血浆 P4 浓度更大（P ⩽0.02）。EST 牛的胚胎长度和前列腺素 E 合酶和干扰素-τ的信使 RNA（mRNA）表达更大（P ⩽0.04）。此外，在第 30 天被诊断为怀孕的 EST 牛在第 20 天的血液 mRNA 表达中具有更高的抗黏液病毒 2（P<0.01）。总之，发情表达在 FTAI 附近时间增强了 B. indicus 牛的妊娠建立因素，包括胚胎发育和干扰素-τ的 mRNA 表达。
