Effect of uterine inflammation and ultrasonically-detected uterine pathology on fertility in the mare.

This study investigates the effect of uterine inflammation and uterine abnormalities detected by ultrasound on horse fertility. The researchers found that incidences of intrauterine fluid collections and uterine cysts were common and resulted in lower pregnancy rates and higher rates of embryonic loss, suggesting a possible link between these factors and horse fertility.

Prevalence of Uterine Abnormalities in Mares

• The research observed a high incidence of intrauterine fluid collections (28%) during dioestrus, a phase of the mare’s reproductive cycle, and uterine cysts (15%) throughout the entire reproductive cycle. These abnormalities were detected using ultrasound technology, indicating their prevalence in mares.

Impact of Uterine Cysts on Pregnancy

• Contrary to the initial hypothesis of the research that uterine cysts do not affect pregnancy in mares, the study results disputed this assumption. The presence of intrauterine fluid collections at the dioestrus stage represented an inflammatory process, signified by high biopsy scores, reduced progesterone concentrations, and a shortened interovulatory duration.

Lower Pregnancy Rates and Increased Embryonic Loss

• Mares with fluid collections during dioestrus had lower rates of pregnancy on day 11 and higher rates of embryonic loss by day 20 compared to those that did not have such collections, suggesting a possible correlation between these intracellular abnormalities and fertility.

The Role of Uterine Inflammation in Embryonic Loss

• The study hypothesized that the high rates of embryonic loss in the experimental herd were due to uterine-induced luteolysis (decomposition of the corpus luteum in the ovary), rather than primary luteal inadequacy, or a deficiency in the progesterone-secreting tissue. This was supported by the progesterone profile and length of interovulatory interval in mares with uterine inflammation.