School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, São Paulo, Brazil.
Department of Animal Science, Texas A&M University, College Station, TX.
J Anim Sci. 2018 Feb 15;96(1):236-249. doi: 10.1093/jas/skx043.
This experiment evaluated the impacts of estrus expression and intensity, estimated by physical activity during a timed-AI protocol, on reproductive performance of Bos indicus-influenced beef cows. A total of 290 lactating, primiparous, and multiparous nonpregnant Nelore × Angus cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device (CIDR) on d -11, a 12.5 mg injection of PGF2α on d -4, CIDR removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of eCG on d -2, and timed-AI on d 0. Cows were fitted with a pedometer behind their left shoulder on d -4. An estrus detection patch was attached to the tail-head of each cow on d -2. Pedometer results were recorded on d -2 and 0. Estrus expression was defined as removal of >50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting total steps from d -4 to -2 (nonestrus basal activity) from total steps from d -2 to 0 (proestrus + estrus period) of each cow. Cows that did not express estrus were classified as NOESTR. Cows that expressed estrus were ranked by net physical activity; those above the median were classified as HIESTR and the remaining cows as LWESTR. Ovarian ultrasonography was performed on d 0 and 7. Blood was collected on d 0, 7, 20, and 30. Pregnancy status was verified by ultrasonography on d 30. Only data from cows responsive to the estrus synchronization protocol were utilized (NOESTR, n = 59; LWESTR, n = 100; HIESTR, n = 98). Diameter of dominant follicle on d 0, corpus luteum volume on d 7, and plasma P4 concentrations on d 7 were greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR and also greater (P ≤ 0.05) for LWESTR vs. NOESTR. Plasma P4 concentrations on d 0 were greater (P < 0.01) in NOESTR vs. HIESTR and LWESTR and similar (P = 0.93) between HIESTR and LWESTR. Whole blood mRNA expression of myxovirus resistance 2 on d 20 was greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR, and similar (P = 0.72) between LWESTR and NOESTR. Pregnancy rates were less (P ≤ 0.04) in NOESTR vs. HIESTR and LWESTR (52.4%, 68.9%, and 73.5%, SEM = 7.2), and similar (P = 0.57) between HIESTR and LWESTR. Hence, expression of estrus during a timed-AI protocol improved ovarian dynamics and pregnancy success, whereas estrus intensity modulated key biological markers associated with fertility but not pregnancy rates in B. indicus-influenced cows beef cows.
本实验评估了在定时人工授精方案中通过身体活动估计的发情表现和强度对印度野牛影响的肉牛繁殖性能的影响。共有 290 头哺乳期、初产和经产未怀孕的尼洛牛×安格斯牛在 d-11 时接受 2 毫克苯甲酸雌二醇和阴道内孕酮（P4）释放装置（CIDR）注射，在 d-4 时接受 12.5 毫克前列腺素 F2α 注射，在 d-2 时除了 0.6 毫克雌二醇环戊酯和 300 国际单位的 eCG 注射以及 d-0 时定时人工授精外，CIDR 去除。d-4 时在牛的左肩部后面安装了计步器。在 d-2 时将发情检测补丁贴在每头牛的尾巴上。d-2 和 0 时记录计步器结果。发情表现定义为 d0 时从斑块上擦掉超过 50%的磨损涂层。通过从 d-4 到-2 的总步数（非发情基础活动）减去从 d-2 到 0 的总步数（发情前+发情期），计算每头牛发情期间的净体力活动。未表现发情的牛被归类为 NOESTR。根据净体力活动对表现发情的牛进行排名；高于中位数的牛被归类为 HIESTR，其余牛被归类为 LWESTR。在 d0 和 7 时进行卵巢超声检查。在 d0、7、20 和 30 时采集血液。在 d30 时通过超声检查确认妊娠状况。仅使用对发情同步方案有反应的牛的数据（NOESTR，n=59；LWESTR，n=100；HIESTR，n=98）。d0 时优势卵泡直径、d7 时黄体体积和 d7 时血浆 P4 浓度在 HIESTR 中大于（P≤0.05）LWESTR 和 NOESTR，LWESTR 也大于（P≤0.05）NOESTR。d0 时血浆 P4 浓度在 NOESTR 中高于（P<0.01）HIESTR 和 LWESTR，在 HIESTR 和 LWESTR 之间相似（P=0.93）。在 d20 时，血液中肌浆网钙ATP 酶 2 的 mRNA 表达在 HIESTR 中高于（P≤0.05）LWESTR 和 NOESTR，在 LWESTR 和 NOESTR 之间相似（P=0.72）。NOESTR 中的妊娠率低于（P≤0.04）HIESTR 和 LWESTR（52.4%、68.9%和 73.5%，SEM=7.2%），HIESTR 和 LWESTR 之间相似（P=0.57）。因此，在定时人工授精方案中表现发情可改善卵巢动态和妊娠成功率，而发情强度调节与生育力相关的关键生物学标志物，但对印度野牛影响的肉牛的妊娠率没有影响。
