Anti-Müllerian hormone levels in relation to ovarian structures, season and age in Lipizzaner broodmares.

Anti-Müllerian hormone (AMH) levels in Lipizzaner broodmares vary depending on the age of the mare and are positively associated with the number and size of ovarian follicles, but do not show seasonal variation.

Study Objective and Background

• The study aimed to measure AMH levels in Lipizzaner mares and examine their relationship with ovarian follicle characteristics, age, and season.
• AMH is produced by granulosa cells in ovarian follicles and is considered an indicator of female fertility and ovarian reserve, reflecting the population of growing follicles.

Methodology

• Twenty-three Lipizzaner mares between 6 and 24 years old participated in the study.
• Mares were divided into two age groups:
  • Group 1: Younger mares aged 6-15 years (n = 11)
  • Group 2: Older mares older than 15 years (n = 12)
• Venous blood samples were collected to measure serum AMH concentration.
• Ovarian activity was monitored by transrectal ultrasonography to count and size ovarian follicles.
• Data were analyzed to detect relationships between AMH levels and follicle number/size, age groups, and season.

Findings

• AMH concentrations showed significant variation between younger and older mares.
• Older mares had significantly lower AMH concentrations compared to younger mares, indicating a decline in ovarian reserve or follicle activity with age.
• There was a positive correlation between AMH levels and:
  • Number of medium-sized ovarian follicles (statistically significant with P = 0.022)
  • Number of large ovarian follicles (P = 0.016)
  • Total follicle count (P = 0.026)
• No significant seasonal effect on AMH concentrations was observed, suggesting that AMH levels remain stable throughout the year in Lipizzaner broodmares.

Implications

• AMH can be used as a biomarker to estimate ovarian follicle population and fertility potential in Lipizzaner mares.
• The decline in AMH with age aligns with the expected decrease in ovarian reserve as mares grow older, which can influence breeding management strategies.
• Stable AMH levels across seasons suggest that time of year does not need to be considered when testing for ovarian reserve using AMH in this breed.

Conclusion

• This research demonstrates that AMH concentration in Lipizzaner broodmares reflects the follicular population and is influenced by age but not seasonal changes.
• These findings support the use of AMH measurement as a reliable tool for assessing reproductive status and managing broodmare fertility over time.