Evaluation of luteolytic activity and reproductive outcomes in ewes following single and split dose cloprostenol during the breeding season

The objective of the present study was to investigate the luteolytic effects of different and split doses of cloprostenol administered during the mid-luteal phase of the estrous cycle in ewes. For this purpose, 147 Anatolian Merino sheep aged 3–5 years were used in the breeding season. The ewes were assigned to three groups. A pre-synchronization was performed to synchronize the estrous periods of the ewes before the treatments were started in all groups, and estrus was monitored. The day of oestrus was accepted as day 0. Afterwards, on day 12 of the estrous cycle, Group I (1 dose) was administered 250 µg of cloprostenol; Group II (½ dose) received 125 µg of cloprostenol; and Group III (2 dose) was administered two doses of cloprostenol: 125 µg on day 12 and an additional 125 µg on day 13, with a 24-hour interval between administrations. No significant differences were observed in estrus rates or the timing of estrus onset among the different prostaglandin administration protocols in ewes. However, in the group that received prostaglandin in split doses, 95% of the ewes exhibited estrus within the first 48 h (P < 0.05). The highest pregnancy rate was observed in the group that received a 1 dose of prostaglandin, although there was no statistically significant difference when compared to the group receiving 2 dose. Additionally, progesterone levels did not show time-dependent variation. In conclusion, although different prostaglandin administration protocols did not affect overall estrus rates, it was determined that the majority of estrus responses occurred within the first 48 h following 2 dose prostaglandin administration. Moreover, pregnancy rates were found to be similar in the 1 dose and 2 dose groups, whereas pregnancy rates decreased following administration of a ½ dose of prostaglandin. Based on these findings, it was observed that sheep responded to all doses during the mid-luteal phase of the estrus cycle.