The fertility increase after misoprostol administration is differently expressed when sheep are inseminated with chilled or frozen-thawed semen

The effect of vaginal administration of misoprostol 6 h prior to artificial insemination (AI) with chilled (CS-AI, n = 95) or frozen-thawed (FTS-AI, n = 163) semen on the site of semen deposition (vaginal AI vs. cervical AI) and on fertility of Saloia ewes was studied. The proportion of intracervical inseminations was not improved by misoprostol. Overall fertility of CS-AI ewes was 24.1% higher after misoprostol treatment when compared to controls (p = 0.015). Intracervically inseminated CS-AI ewes presented a higher (p = 0.049) fertility rate after misoprostol treatment than controls. The fertility increase (83.3% vs. 40%) induced by misoprostol in vaginal AI was non-significant due to a smaller population. Overall fertility of FTS-AI ewes was 9.2% higher (p = 0.13) after misoprostol treatment. Fertility of FTS-AI in control and treated ewes was significantly higher in inseminations performed in the cervix than in the vagina (p < 0.05).Results show a positive effect of misoprostol in increasing fertility of Saloia ewes inseminated with chilled semen. Misoprostol mediated increase of fertility was of lower magnitude after inseminations with frozen-thawed semen, showing that the negative effect of freezing-thawing process could not be completely reversed by the drug.Furthermore, misoprostol improvement of fertility was not associated with any increase on the proportion of cervical inseminations, suggesting that other mechanisms besides a significant opening of cervical lumen seem to have occurred.