Abstract
It has been well proved that melatonin participates in the regulation of the seasonal reproduction of ewes. However, the effects of short term treatment of melatonin on ewe’s ovulation are still to be clarified. In this study, the effects of melatonin on the number of embryos harvested from superovulation, and the pregnant rate in recipients after embryo transferred have been investigated. Hu sheep with synchronous estrus treatment were given melatonin subcutaneously injection (0, 5, and 10 mg/ewe, respectively). It was found that the estrogen level in the group of 5 mg melatonin was significantly higher than that of other two groups at the time of sperm insemination (p < 0.05). The pregnant rate and number of lambs in the group of 5 mg melatonin treatment was also significantly higher than that of the rests of the groups (P < 0.05). In another study, 31 Suffolk ewes as donors and 103 small-tailed han sheep ewes as recipients were used to produce pronuclear embryo and embryo transfer. Melatonin (5 mg) was given to the donors during estrus. The results showed that, the number of pronuclear embryos and the pregnancy rate were also significantly higher in melatonin group than that in the control group. In addition, 28 donors and 44 recipient ewes were used to produce morula/blastocyst and embryo transferring. Melatonin (5 mg) was given during estrus. The total number of embryos harvested (7.40 ± 1.25/ewe vs. 3.96 ± 0.73/ewe, P < 0.05) and the pregnant rate (72.3 ± 4.6% vs. 54.7 ± 4.0%, P < 0.05) and number of lambs were also increased in melatonin group compared to the control group. Collectively, the results have suggested that melatonin treatment 36 hours after CIDR withdrawal could promote the number and quality of embryos in vivo condition and increased the pregnant rate and number of lambs.
Highlights
The estrous cycles of most sheep are regulated by the switch of seasons
The effects of melatonin on Follicle stimulating hormone (FSH), luteinizing hormone (LH) and E2 were evaluated at three different time points (Table 1)
There was no difference in melatonin levels between the three groups at the time of CIDR withdrawal and estrus
Summary
The estrous cycles of most sheep are regulated by the switch of seasons. With the reduced photoperiod and increased melatonin level, ewes adjust GnRH level and estrus cyclesHow to cite this article Song Y, Wu H, Wang X, Haire A, Zhang X, Zhang J, Wu Y, Lian Z, Fu J, Liu G, Wusiman A. 2019. Melatonin improves the efficiency of super-ovulation and timed artificial insemination in sheep. A various of ROS (reactive oxygen species such as OH.− and O.2−) will damage the DNA and the lipid of cell membrane, accelerate apoptosis in reproductive system (Agarwal, Gupta & Sharma, 2005). The reason is that oxidative stress reduces the quality of oocytes which is an important factor for sheep fertility. Melatonin scavenges OH−, H2O2 and other reactive oxygen species; it contributes to effectively reduce oxidative DNA damage and cell apoptosis during ovulation (Miyamoto et al, 2010). Melatonin reduces oxidative damage to mitochondrial DNA (Galano, Tan & Reiter, 2018). Melatonin improves the quality of bovine oocyte, oocyte maturation, efficiency of in vitro fertilization and embryo development (He et al, 2016b). Melatonin is probably the key factor to improve fecundity by improving the quality of oocytes in mammals
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