Fluctuations of antimüllerian hormone, ovarian follicular reserve, and antioxidant status throughout the estrous cycle in aged mares.

The research article investigates the impact of aging on the fertility of mares. The study specifically focuses on the daily changes in the dominant follicle dynamics, hemodynamics, antimüllerian hormone (AMH), enzymes, antioxidants, and ovarian hormones during the estrous cycle.

Research Methodology

• The research team compared old mares that were over 20 years old and younger native mares that were less than 10 years old.
• Ovaries of these mares were scanned during six different estrous cycles from March 2022 to August 2023 with Doppler ultrasound.
• Data points captured included the dominant follicle (DF) diameter and color area, the corpus luteum (CL) diameter, and the uterine horn area and color area.
• Blood samples were collected with each ultrasound and Doppler scanning, and various parameters including AMH, estradiol (E2), progesterone (P4), cholesterol, myeloperoxidase, catalase, glutathione peroxidase, lactate dehydrogenase (LDH), alkaline phosphatase, and nitric oxide (NO) concentrations were determined.

Findings

• The study found that age significantly affected several aspects including the dominant follicle area, color area, the corpus luteum area, the uterine horn area, the ovarian artery pulsatility index, estradiol, cholesterol, LDH, and NO.
• Aging tended to decrease the dominant follicle antrum diameter but significantly decreased its area, antrum area, and color area percent. Similarly, the uterine horn diameter and area, estradiol, total cholesterol, LDH, and NO levels also decreased with age. In contrast, the study found that aging increased the corpus luteum area and the ovarian artery PI.

Conclusions

• Aging in mares did not disturb AMH, the ovarian macro-environmental dynamics, follicle growth, and recruiting.
• However, it was found that the disrupted blood flow mediators, enzymes, and antioxidant status, which were affected by aging, may influence the intrafollicular mediators and potentially have an impact on the oocyte quality in the mares.