Use of GnRH for Synchronization of the Follicular Wave in Assisted Reproductive Technologies in Sheep: A Preliminary Study

• Main Authors: Aina Año-Perello, Zurisaday Santos-Jimenez, Teresa Encinas, Paula Martinez-Ros, Antonio Gonzalez-Bulnes
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Animals
• Subjects: assisted reproduction; estrus synchronization; follicle; GnRH; sheep
• Online Access: https://www.mdpi.com/2076-2615/10/7/1208

The present study aimed to set up a short-term protocol for synchronization of follicular wave emergence in sheep, concomitant with estrus synchronization, which would improve ovarian response in assisted reproductive technologies. Administration of a single GnRH dose, concomitant with the insertion of a progesterone-loaded CIDR device, caused regression of gonadotrophin-dependent follicles ≥4 mm in all the GnRH-treated sheep and in around 80% of the controls treated only with CIDR (<i>p</i> < 0.05). Similar percentages of ewes lost all follicles (around 70%) or only the largest one (around 30%) in both groups. Hence, 54.1% and 70% of the sheep lost all large follicles and initiated a new follicular wave in the control and GnRH groups, respectively (<i>p</i> < 0.05). The remaining sheep showed follicles that were still not dependent of luteinizing hormone (LH). So, in fact, all the sheep had non-dominant follicles after treatment. In conclusion, a treatment including GnRH at CIDR insertion would offer a time- and cost-efficient protocol for inducing follicular turnover and synchronizing a new follicular wave at any stage of the estrous cycle.