Melatonin improves the efficiency of super-ovulation and timed artificial insemination in sheep

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.

Effects of Duodenal 5-Hydroxytryptophan Perfusion on Melatonin Synthesis in GI Tract of Sheep

“…For example, it improves the meat quality and quantity of cashmere goats [13,14], reduces somatic cell count and mastitis in dairy cattle to improve the quality of the milk [15,16]. Currently, in husbandry industrial, the methods used to regulation of MT levels in animals are primarily to alter the light/dark cycle of the environments [17,18], or by implantation [19,20], injection [21], and oral administration [22] of MT. As to the exogenous melatonin administration, several factors should be considered including its bioavailability, acting duration, economic benefit, and delivery methods [22].…”

The Melatonin Treatment Improves the Ovarian Responses After Superstimulation in Thai-Holstein Crossbreeds Under Heat Stress Conditions

“…To increase the confidence of the experiment, each cow received the same alternate treatment in testing periods 3 and 4. In the melatonin group, cows received 18 mg./50 kg of body weight simultaneously with GnRH injection ( 33 ), while cows in the control group received none. The superovulatory responses and ova/embryo recovery were determined.…”

Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation

“…Exogenous melatonin can be administered via subcutaneous implants, which prolong the breeding season, and thus enhance the proportion of pregnant ewes. During the ovulatory process, reactive oxygen species (ROS) produced inside the follicles cause stress that ultimately induces two cell developmental blocks, resulting in poor oocyte quality [ 118 , 119 ], which is an important factor for sheep fertility [ 119 ]. Melatonin concentrations are several times higher in the follicles than in the serum in human preovulatory follicles [ 114 ].…”

“…The high-prolificacy aged Rasa Aragonesa ewes treated with melatonin showed improved embryo viability after a conventional superovulation protocol [ 123 ]. Similarly, melatonin injected 36 h after CIDR removal was followed by a significant increase in estrogen level and the number of pronuclear embryos, which ultimately increased the pregnancy rate and number of lambs [ 119 ]. In addition, melatonin subcutaneous implants before superovulation and estrus synchronization at the rate of 40 or 80 mg increased the CL number (13.4 and 15.1) compared to ewes in the control group (8.8).…”

“…This demonstrates that melatonin implants have a protective effect on oocyte quality and can promote the donor’s response to superovulation, which provides more high-quality embryos for microinjection and enhances the ability of the recipients to support transgenic embryonic development. Melatonin injection in the neck during estrus increases the level of melatonin and estradiol in the blood, which has a beneficial effect on embryo production and pregnancy rate [ 118 , 119 ].…”