Abstract
Simple SummaryThe use of equine chorionic gonadotrophin (eCG) in protocols for estrus synchronization in sheep is currently challenged, so it is necessary to implement alternatives (i.e., human chorionic gonadotropin; hCG), mainly during the anestrous season. Therefore, we compared the reproductive outcomes, including estrus induction, ovulatory follicle dynamics, and pregnancy outputs in anestrus Dorper sheep treated with insertion of one intravaginal progesterone-loaded CIDR + either saline, eCG, or hCG. The administration of hCG at the time of CIDR removal was effective at inducing estrus, resume ovulations, and ovarian cyclicity, yet, in a narrow window of time, it is a scenario that may limit the implementation of an artificial insemination protocol.This research aimed to evaluate whether the administration of hCG at the time of removal of a progesterone device may be effective at inducing estrus and ovulations in sheep during the natural seasonal anestrous, by comparing reproductive outputs (induction and duration of estrus, follicle development, ovulation, ovulation rate, and pregnancy rates) in ewes treated with eCG or only saline solution at the time of CIDR removal. Whereas results demonstrated no response in the control non-treated group, the largest rate of narrowly synchronized estrus signs and ovulations occurred in the eCG-group. The administration of hCG was effective at inducing estrus, promote follicular growth and a delayed yet significant ovulation (>84%) on day 10 after CIDR removal; moreover, an increased embryonic implantation rate was also observed. Moreover, if the hCG ewes remain exposed to active males for some days, said strategy could be adopted, aiming to induce pregnancies by natural mating in a short period of time.
Highlights
The reproductive management of sheep, during both the reproductive and nonreproductive seasons, mainly relies on the use of progesterone-based protocols combined with the administration of a single dose of equine chorionic gonadotrophin at the end of the progesterone treatment [1], which induces the ovulation and allows its synchronization
Diverse laboratories around the world are developing a synthetic equine chorionic gonadotrophin (eCG) by recombinant deoxyribonucleic acid (DNA) technology, which may function in a similar way as follicle stimulating hormone (FSH) and luteinizing hormone (LH) [5,6,7,8,9]
Unavailability of eCG is a critical problem for the management of reproduction in farm animals since the different attempts of using other hormones, such as FSH, LH, gonadotrophin-releasing hormone (GnRH), or hCG have not found similar outcomes as eCG [4]
Summary
The reproductive management of sheep, during both the reproductive and nonreproductive seasons, mainly relies on the use of progesterone-based protocols combined with the administration of a single dose of equine chorionic gonadotrophin (eCG) at the end of the progesterone treatment [1], which induces the ovulation and allows its synchronization. It is essential when implementing artificial insemination, but it is of high interest for increasing the number of twin births [2]. These studies were performed during reproductive season and the differences in the follicle dynamics occurring during the seasonal anestrous [18], due to the different patterns of release of LH [19], are currently well known
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
