The present study aimed to evaluate the effect of a single intramuscular injection of melatonin on response of oestrus, rate of conception, ovarian and uterine blood supply during the non‐breeding season. Melatonin powder was dissolved in dimethyl sulfoxide (DMSO) and olive oil and injected in two dose of 25 mg (MEL‐1; n  = 10) and 50 mg (MEL‐2; n  = 10) in May. Ten ewes were served as the control (CON). Results showed that oestrous response was higher in the MEL‐2 group than in other groups (p  < .01). The time to onset of oestrus in both the MEL‐1 and MEL‐2 groups was significantly shorter, compared with the CON group (p  < .01). Pregnancy rates reached 80% and 90% at 45 days of gestation. Doppler indices of the right and left ovarian artery were lower in the melatonin groups than in normal groups (p  < .01). Both Doppler indices in uterine arteries were not different among two treatment groups (p  > .05), but there was a significant difference when compared with the CON group (p  < .01), no difference found between two treatment group in the Doppler velocities of middle uterine arteries (p  > .05). In conclusion, the definite changes in the studied parameters showed two novel findings; (a) the increase in melatonin dose results in increasing the blood flow expressed by increased Doppler velocities in fatty tailed ewes, (b) as well as, melatonin can initiate the breeding season regardless of the season earlier by 1–2 months in ewes.

中文翻译：

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较高剂量的褪黑素会影响卵巢和子宫中动脉的血管血流，并在无环母羊中更早地诱发发情。

本研究旨在评估在非繁殖季节单次肌内注射褪黑激素对发情反应，受孕率，卵巢和子宫血液供应的影响。将褪黑激素粉末溶解在二甲亚砜（DMSO）和橄榄油中，并 于5月份分别注射25 mg（MEL-1; n  = 10）和50 mg（MEL-2; n = 10）两种剂量。十只母羊作为对照（CON）。结果显示，MEL-2组的强烈反应比其他组高（p  <.01）。与CON组相比，MEL-1和MEL-2组的发情时间明显缩短（p <.01）。妊娠45天时的怀孕率分别达到80％和90％。褪黑激素组的左，右卵巢动脉多普勒指数低于正常组（p  <.01）。在两个治疗组之间，子宫动脉的两个多普勒指数没有差异（p  > .05），但与CON组相比有显着差异（p  <.01），两个治疗组的多普勒速度没有差异中间子宫动脉（p > .05）。总之，研究参数的确定变化显示了两个新颖的发现。（a）褪黑激素剂量的增加导致脂肪尾母羊多普勒速度增加所表示的血流量增加，（b）褪黑素可以在母羊中提前1-2个月而不管季节开始了。