Time of ovulation and pregnancy outcomes obtained with the prostaglandin-based protocol Synchrovine for FTAI in sheep

•A prostaglandin-based protocol to synchronize ovulation in sheep was tested.•It is effective to control luteal function, follicular dynamics and time of ovulation.•Ovulation is synchronized in a narrow 24 h period in all treated ewes.•Pregnancy rate was improved using intrauterine semen deposition.•Pregnancy rate was not affected by eCG administration at the end of the protocol.

The objective of the present study was to determine the ovarian response induced with the prostaglandin-based protocol Synchrovine (two doses of PGF2α given 7 d apart), as well as the fertility after FTAI. In Experiment 1, 15 females received the Synchrovine protocol using two different PGF2α analogues (Delprostenate vs. D-Cloprostenol). No differences in estrus response, time of ovulation and follicular dynamics were found between both groups (P < 0.05). The ovulation after Synchrovine was synchronized in a similar mean interval (68.8 ± 7.1 h) than when the females received a single dose of PGF2α (70.2 ± 20.7 h; P=NS), but the dispersion between the first and the last ovulation was reduced with this protocol (range 60-84 h vs. 24-96 h, respectively; P < 0.05). In experiment 2, 318 ewes were treated with the Synchrovine protocol and cervical FTAI was performed using different sperm cell concentrations. Pregnancy rate was higher using 200 × 106 and 100 × 106 sperm cells (38.2%, 39/102; and 34.9%, 38/109, respectively) than using 50 × 106 (23.4%, 25/107, P < 0.05). In Experiment 3, 444 ewes received the Synchrovine protocol and were assigned to receive 300 IU of eCG or not at the moment of the second dose of PGF2α, and cervical FTAI was performed 42 h or 48 h after the second dose of PGF2α. No effect was found related to the eCG administration nor the time of insemination. In Experiment 4, 342 received cervical or intrauterine insemination after treatment with the Synchrovine protocol, resulting in greater pregnancy rate for intrauterine insemination than cervical insemination (52.5%, 90/171 vs. 31%, 53/171, P < 0.05). These experiments demonstrate that the Synchrovine protocol effectively induces luteolysis, estrus and ovulation in most of the treated females, and ovulation is synchronized into a narrow window of 24 h. Pregnancy rate obtained with cervical FTAI is around 30-45%, with similar results using 100 × 106 or 200 × 106 sperm cells, the eCG administration seems not to be necessary, the type of PGF2α analogue does not appear relevant, and fertility is improved with intrauterine semen deposition.