Study identifies PBIE risk factors in warmblood mares

A new retrospective study in Equine Veterinary Journal found that older warmblood mares, embryo donor mares, and mares inseminated with chilled-transported semen were more likely to develop persistent breeding-induced endometritis, or PBIE. The analysis covered 769 mares across 1,745 estrous cycles and defined PBIE as more than 2 cm of intrauterine fluid detected the day after insemination. Mares aged 14 years or older had higher PBIE rates than mares 6 years or younger, embryo donors were at higher risk than broodmares, and chilled semen was associated with more PBIE than frozen-thawed semen. Even so, PBIE itself did not significantly reduce pregnancy or embryo recovery in this dataset, which the authors said likely reflects the benefit of routine post-breeding treatment. (research-portal.uu.nl)

Why it matters: For equine veterinarians and reproduction teams, the study sharpens risk stratification at the start of the breeding cycle. PBIE is already recognized as a common cause of subfertility in mares, especially when uterine clearance is impaired, and older or repeatedly bred donor mares have long been considered more vulnerable. This new dataset adds practice-level evidence that age, donor status, and semen type can help identify mares that may benefit from closer post-breeding monitoring, early ultrasound checks for fluid, and prompt but simple interventions such as oxytocin, lavage, or other clinician-selected protocols. (research-portal.uu.nl)

What to watch: Watch for whether this paper changes breeding-management protocols for donor mares and older mares, especially around semen selection, post-breeding surveillance, and standardized treatment pathways. (research-portal.uu.nl)