Anti Mullerian Hormone as a potential biomarker of stallions fertility

Abstract

Anti-Müllerian hormone (AMH) is an inhibiting hormone that is crucial for sexual differentiation during foetal development. It continues to influence reproductive health into adulthood. While its role in mares has been extensively studied, its function in stallion fertility is less well understood. Secreted by Sertoli cells, AMH concentrations are notably high before puberty, then decrease during adolescence as rising testosterone levels actively regulate its expression. The AMH concentration is valuable for diagnosing cryptorchidism and has been used to evaluate testicular activity in behavioural studies, although its direct relationship to fertility remains underexplored. Recent findings have shown a correlation between low serum AMH levels and poor semen quality in infertile men and dogs, suggesting its potential as a biomarker for reproductive health in stallions. Thus, the objective of this study was to evaluate whether AMH concentrations can be used as an indicator of potential fertility in stallions. Jugular blood samples were collected from 10 breeding stallions and 1 stallion with known testicular degeneration; breeding results from the same season were recorded. Based on anamnesis, the stallions were categorized into two groups: SG0 (good breeders) and SG1 (poor breeders) according to empirical observations of responsible veterinarians throughout the stallion's breeding career. The AMH concentrations were measured using an ELISA (Beckman-Coulter Gen II, California), followed by statistical analyses (t-test and linear regression) to evaluate the relationship between AMH concentrations and breeding outcomes. The AMH concentrations ranged from 7.71 ng/ml to 35.91 ng/ml for all stallions (median 14.60 ng/ml), 9.31-35.91 ng/ml for SG0 (median 21.91 ng/ml) and 7.71-14.60 ng/ml for SG1 group (median 13.27 ng/ml). The significant differences in AMH concentrations between the two groups, with the SG0 group having higher AMH concentration than the SG1 group (t-test: t = 3.53, p = 0.008). The stallion with testicular degeneration had the lowest AMH concentration in the sample (7.71 ng/ml). A linear regression model demonstrated a positive relationship between AMH levels and pregnancy success rates: a 1 ng/ml increase in AMH concentration was associated with a 2 percentage point increase in success rate (p = 0.033). These results suggest that AMH concentration could serve as a predictor for stallion fertility. However, the study has some limitations, including the small sample size and the need to include additional variables in a multiple regression model. The current model accounts for 41.41% of the variance in fertility outcomes. In conclusion, this study presents promising preliminary evidence supporting the use of AMH concentration as a biomarker for stallion fertility. It serves as a valuable pilot study for future research with larger samples and more comprehensive models that include other factors influencing fertility.

We are grateful to FORMAS, Stockholm, for funding (2018–01083).