USDA-ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT 59301, USA.
J Anim Sci. 2012 Jan;90(1):207-11. doi: 10.2527/jas.2010-3564. Epub 2011 Aug 19.
Pregnancy loss in beef cattle after d 28 of gestation is variable, but it has been reported to be as great as 14% and has been related to transportation or handling stress. The primary objective of this study was to determine whether activation of the hypophyseal-adrenal axis with ACTH would mimic a stressful response and cause pregnancy loss in beef cattle. A secondary objective was to determine if a single injection of the PG synthesis inhibitor flunixin meglumine would attenuate the stress response and suppress serum PGF(2α) concentrations to prevent pregnancy loss. Forty nonlactating beef cows that were 34 ± 0.33 d pregnant were used for this study. In a 2 × 3 factorial arrangement, cows were randomly assigned to receive ACTH [0 or 0.5 IU/kg of BW, intramuscularly (i.m.)] at 0 and 2 h of the study and flunixin meglumine (0, 1.1, or 2.2 mg/kg of BW, i.m.) at 0 h. Blood samples were collected from all cows at 0 h and every 30 min for 4 h to measure serum cortisol and PGF(2α) metabolite (PGFM) concentrations. Rectal temperature was collected for each cow at 0, 120, and 240 min. Pregnancy exams were conducted 31 and 58 d after treatment by transrectal ultrasonography, and the presence of a fetal heartbeat was used as an indicator of fetal viability. Serum cortisol concentration was affected (P < 0.01) by ACTH, time, and the interaction of ACTH × time, but not by flunixin meglumine (P ≥ 0.14) or any other interactions. Cortisol concentrations increased (P < 0.01) in the serum of ACTH-treated cows immediately after ACTH treatment and remained increased (P < 0.01) throughout the 4-h sampling period. Serum PGFM concentration was not affected by ACTH (P = 0.97) or by any interactions (P > 0.35) with ACTH, but was affected (P < 0.01) by flunixin meglumine, time, and the interaction of flunixin meglumine × time. Regardless of dosage (1.1 or 2.2 mg/kg of BW), flunixin meglumine decreased (P < 0.01) serum PGFM concentrations in both ACTH-treated and control cows for the duration of the study. Although ACTH treatment induced a prolonged increase in serum cortisol concentration, none of the cows used in this study lost a pregnancy. In conclusion, the activation of the hypophyseal-adrenal axis with ACTH increased serum cortisol concentrations but did not increase serum concentrations of PGFM or cause pregnancy loss during early gestation in cows. Flunixin meglumine treatment suppressed serum PGFM concentrations in control and ACTH-treated cows.
妊娠 28 天后的肉牛流产率各不相同，但据报道高达 14%，与运输或处理应激有关。本研究的主要目的是确定促肾上腺皮质激素（ACTH）是否会激活垂体-肾上腺轴并引起肉牛流产，从而模拟应激反应。次要目的是确定单次注射前列腺素合成抑制剂氟尼辛葡甲胺是否会减弱应激反应并抑制血清 PGF（2α）浓度，以防止流产。本研究使用了 40 头非泌乳期、妊娠 34 ± 0.33 天的肉牛。采用 2×3 析因设计，将牛随机分为两组，分别在研究的 0 小时和 2 小时肌肉注射（i.m.）0 或 0.5 IU/kg BW 的 ACTH，0 小时肌肉注射 0、1.1 或 2.2 mg/kg BW 的氟尼辛葡甲胺。所有牛在 0 小时和 4 小时内每隔 30 分钟采集一次血液，以测量血清皮质醇和 PGF（2α）代谢物（PGFM）浓度。在 0、120 和 240 分钟时为每头牛采集直肠温度。治疗后 31 和 58 天通过直肠超声检查进行妊娠检查，并使用胎儿心跳作为胎儿存活的指标。血清皮质醇浓度受 ACTH（P < 0.01）、时间和 ACTH × 时间的相互作用影响，但不受氟尼辛葡甲胺（P ≥ 0.14）或任何其他相互作用的影响（P > 0.35）。ACTH 处理后，ACTH 处理的牛血清中的皮质醇浓度立即升高（P < 0.01），并在整个 4 小时采样期间持续升高（P < 0.01）。ACTH 或与 ACTH 的任何相互作用（P > 0.35）均未影响血清 PGFM 浓度（P = 0.97），但影响了血清 PGFM 浓度（P < 0.01），时间和氟尼辛葡甲胺×时间的相互作用。无论剂量（1.1 或 2.2 mg/kg BW）如何，氟尼辛葡甲胺均降低了 ACTH 处理和对照牛的血清 PGFM 浓度（P < 0.01），持续整个研究期间。尽管 ACTH 处理诱导了血清皮质醇浓度的延长升高，但本研究中没有牛流产。总之，ACTH 激活垂体-肾上腺轴增加了血清皮质醇浓度，但并未增加妊娠早期牛的血清 PGFM 浓度或导致流产。氟尼辛葡甲胺治疗抑制了对照和 ACTH 处理牛的血清 PGFM 浓度。
