Effects of intrauterine ozone insufflation in eleven subfertile mares: a case series.

Overview

• This study evaluated the effects of intrauterine ozone gas insufflation as a treatment for infertility in mares with persistent breeding-induced endometritis who did not respond to conventional therapies.
• After treatment, most mares conceived and gave birth to live foals, with evidence suggesting ozone may positively influence uterine tissue healing.

Background

• Persistent breeding-induced endometritis is a common reproductive problem in mares, characterized by chronic inflammation and fibrosis of the uterus.
• This condition results in decreased fertility and often resistance to standard treatments like antibiotics and uterine lavage.
• Recent research has proposed intrauterine ozone (O₃) therapy due to its known antimicrobial and anti-inflammatory properties.

Study Design

• The study was a case series involving eleven subfertile mares infertile for at least one year despite multiple insemination attempts.
• Each mare underwent a low-volume uterine lavage and endometrial biopsy during their first estrous cycle as a baseline assessment.
• Following this, mares received intrauterine insufflation of a mixture of oxygen–ozone gas for three consecutive days.
• In the next estrous cycle, lavage and biopsy were repeated, and mares were inseminated with fresh or fresh-cooled semen.
• Pregnancy was checked 14 days after ovulation and monitored through to foaling.

Results

• Out of the eleven mares, ten (90.9%) became pregnant following treatment.
• Nine mares (81.8%) successfully delivered a live foal.
• Post-treatment biopsies revealed a significant increase in CD163+ M2 macrophages.
• CD163+ M2 macrophages are involved in tissue remodeling and healing, indicating ozone may promote uterine recovery.

Conclusions and Implications

• Ozone therapy appears to have a beneficial effect on fertility restoration in mares with persistent breeding-induced endometritis refractory to conventional treatment.
• The increase in M2 macrophages suggests ozone may modulate the immune environment of the uterus to favor healing rather than chronic inflammation.
• These promising results could offer a new therapeutic avenue to improve reproductive outcomes in subfertile mares.
• However, as this was a small case series, further controlled studies are needed to confirm efficacy, optimize treatment protocols, and ensure safety.