Effects of intrauterine ozone therapy on oxidative stress and fertility in mares with post-breeding persistent endometritis

• Grant number: 23/15910-4
• Support Opportunities: Scholarships in Brazil - Master
• Start date: August 01, 2024
• End date: July 31, 2026
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Eneiva Carla Carvalho Celeghini
• Grantee: Ellen Lara Miguel
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Persistent post-breeding endometritis is the most common reproductive disorder in horses and causes significant losses in breeding programs, as it is the main cause of infertility and is also associated with embryonic death and abortions. In view of the significant demand for alternative treatments for endometritis, ozone therapy stands out. Although it seems promising, there is still a lack of accurate scientific information on its effectiveness in eliminating the inflammatory process and on the possible effects of its application. The aims of this study are to evaluate the efficacy and effects of intrauterine ozone therapy on post-breeding endometritis in terms of systemic and local oxidative stress and the fertility index. To this end, the estrous cycles of 25 mares will be used during two reproductive seasons. The mares will undergo daily follicular and uterine monitoring by palpation and transrectal ultrasound. Ovulation will be induced in the presence of a follicle e35mm and uterine morphoechogenicity >3 (1-4). Artificial insemination (AI) will be carried out immediately after ovulation with frozen semen, which will be subjected to microbiological analysis. The mares will be evaluated immediately before AI and 48 hours after AI by B-mode, color Doppler (score from 0 to 4) and spectral (RI, 0-1) ultrasound, endometrial cytology and microbiology, as well as local and systemic oxidative stress levels. The diagnosis of persistent endometritis after breeding will be based on endometrial cytology 48 hours after AI. Mares positive for post-breeding endometritis (>10% PMN) will be randomly assigned to two uterine treatments: one will consist of uterine lavage with sodium ringer's lactate (RL, n=12), while the other will consist of uterine lavage with ozonized RL (O3, n=12). The treatments will be carried out immediately after diagnosis (48h post-IA). After 8 hours of treatment, uterine and blood samples will be taken to measure oxidative stress and assess uterine vascularization, and after 24 hours, blood samples will be taken to measure oxidative stress and assess uterine vascularization. Mares with a negative pregnancy diagnosis will be followed up again for AI, with each estrous cycle being considered the "n" sample. The data will be evaluated by ANOVA and the means compared using the Tukey test. Fertility will be assessed using Fisher's exact test, considering p d0.05. This research project will provide important information for understanding the effects of ozone therapy on the uterine recovery of mares with persistent post-foaling endometritis, as evidenced by a set of diagnostic tools, allowing the identification of the effects of oxidative stress and fertility.