Controlling the success of superovulatory treatments in ewes: Comparing laparoscopy to transrectal and transvaginal ultrasonography

In small ruminants, assessing the success of superovulatory treatments can be challenging, as there is considerable variability between individual animals. The current "gold standard" for examination of the superovulated ovaries is laparoscopy. B-mode ultrasonography with a transrectal or transvaginal transducer can also be used to locate the ovarian structures.In this study, 23 Merino ewes were used to test two types of ultrasonographic examination techniques against laparoscopy.The ewes were treated with long-term (12 days) progesterone treatment followed by a single injection of eCG (1000 IU) at removal of the progesterone sponge. The animals were examined two days after sponge removal and 7 days after the first examination.The chance of localizing the ovaries was significantly higher with the transrectal method than with the vaginal ultrasonography (P > 0.05). In cases when the ovary was successfully visualized, there was a significant difference between the number of ovarian structures (antral follicles and corpora lutea) detected by transrectal ultrasonography and laparoscopy (P < 0.01). There was no significant difference between intravaginal examination and laparoscopy in this regard.The current results are promising in the usefulness of vaginal ultrasonography as an alternative to the more commonly used transrectal technique.However, more research is needed to evaluate if either the transrectal or the vaginal ultrasound examination can be completely reliable in assessing the results of a superovulatory treatment.