This study hypothesizes that melatonin with exogenous progesterone (CIDR) can improve follicular, luteal, ovarian and uterine haemodynamic of heat‐stressed cows. Holstein cows (N = 12) studied for two spontaneous oestrous cycles during winter then divided equally during summer into the CIDR group received CIDR for 7 days and the melatonin group (Mel) received three injections of melatonin (75 mg/head) at the CIDR insertion, removal and ovulation days. Blood samples were collected to assay oestradiol (E2), progesterone (P4) and nitric oxide (NO). On day 0 (Ovulation), Mel had more small follicles (p < .05), higher ipsilateral and contralateral ovarian arteries (Ov.A.) peak systolic velocity (PSV), higher ipsilateral uterine artery (Ut.A.) PSV (p = .031) and blood flow volume (BFV), also Mel elevated contralateral Ut.A. PSV and BFV (p < .0001) but lowered contra Ut.A. pulsatility index (PI, p < .0001), E2 (p < .01) and NO (p < .0001). Mel increased the corpus luteum diameter (CL, p < .001), coloured area (p < .007) and P4 (p < .0001) on day 5 and reduced them (p < .05; p < .01) on Day 14. On day 10, Mel obtained CL diameter (p < .03) and coloured area (p < .002) of spontaneous that was higher than CIDR and decreased P4 (p < .003). Mel increased CL diameter, area and coloured area and decreased them thereafter. Mel increased the ipsilateral ovarian and uterine arteries PSV and BFV before ovulation and until day 8. Mel increased P4 and decreased NO until days 6 and 14. In conclusion, the improvement in follicular, luteal, ovarian and uterine haemodynamic and the decrease of NO production proved our hypothesis Melatonin doses higher than 75 mg/head is recommended to improve the heat‐stressed cow's fertility.

中文翻译：

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褪黑激素和 CIDR 改善了循环奶牛的卵泡和黄体血流动力学、子宫和卵巢动脉血管灌注、卵巢激素和一氧化氮

本研究假设褪黑激素和外源性黄体酮 (CIDR) 可以改善热应激奶牛的卵泡、黄体、卵巢和子宫血流动力学。荷斯坦奶牛 ( N  = 12) 在冬季研究了两个自发的发情周期，然后在夏季平均分为 CIDR 组接受 CIDR 7 天，褪黑激素组 (Mel) 在 CIDR 接受了 3 次褪黑激素注射 (75 毫克/头)插入、移除和排卵天数。收集血液样本以测定雌二醇 (E2)、孕酮 (P4) 和一氧化氮 (NO)。在第 0 天（排卵），Mel 有更多的小卵泡 ( p  < .05)，更高的同侧和对侧卵巢动脉 (Ov.A.) 峰值收缩速度 (PSV)，更高的同侧子宫动脉 (Ut.A.) PSV (磷 = .031) 和血流量 (BFV)，Mel 也升高了对侧 Ut.A。PSV 和 BFV ( p  < .0001) 但相对 Ut.A. 搏动指数 (PI, p  < .0001)、E2 ( p  < .01) 和 NO ( p  < .0001)。Mel 在第 5 天增加黄体直径 (CL, p  < .001)、有色区域 ( p  < .007) 和 P4 ( p < .0001) 并在第 5 天减少它们 ( p  < .05; p  < .01) 14.在第10天，梅尔获得CL直径（p  <0.03）和有色区域（p  <0.002）的自发，除CIDR较高，减少P4（p < .003）。Mel 增加了 CL 直径、面积和有色面积，然后减少了它们。Mel 在排卵前和第 8 天增加同侧卵巢和子宫动脉 PSV 和 BFV。Mel 增加 P4 并减少 NO 直到第 6 天和第 14 天。总而言之，卵泡、黄体、卵巢和子宫血流动力学的改善和 NO 产生的减少证明了我们的假设 建议使用高于 75 毫克/头的褪黑激素剂量来提高热应激奶牛的生育能力。