191 Anti-Müllerian hormone: how early can it be used as a biomarker for future in vitro embryo production in Bos taurus cattle?

Anti-Müllerian hormone (AMH) in cattle is associated with embryo yield after in vitro embryo production (IVEP). However, the ability of AMH determination early in life to serve as a predictor of future embryo yield remains unknown. The aims of this study were to assess (1) changes in AMH from birth to 365 days and (2) the association between AMH determined at different ages and IVEP outcomes at 365 days. Holstein heifers (n = 113) had plasma samples collected from birth (0 days) to 308 days of age at 28-day intervals. At ~365 days (range 326–401) a plasma sample was collected, and heifers were submitted to IVEP. Briefly, follicular wave emergence was synchronized by follicle ablation and an intravaginal P₄ device (CIDR, Zoetis) was inserted. Superstimulation consisting of four 50-mg administrations (12 h apart) of porcine follicle-stimulating hormone (pFSH; Folltropin-V, Vetoquinol) were initiated 36 h later. Ovum pickup (OPU) was performed 44 h after the last pFSH and cumulus–oocyte complexes (COCs) were subjected to IVEP. Samples were assayed using a bovine AMH ELISA (AnshLabs). Data were analysed using correlation analysis and generalized linear mixed models. Circulating AMH was affected by age (P < 0.01) presenting a constant increase from 0 (278 ± 40 pg mL⁻¹) to 84 days (1647 ± 145 pg mL⁻¹) and then a decrease until 224 days (485 ± 41 pg mL⁻¹); however, no differences were observed thereafter. Circulating AMH at all ages was positively correlated (P < 0.05) with AMH at 365 days, except at 0 and 140 days (P > 0.05). Correlations, however, were weak (r = 0.2 to 0.4) at 28 and 56 days, moderate (r = 0.4 to 0.6) at 84 to 196 days, and strong (r = 0.6 to 1) at 224 to 308 days. Positive correlations (P < 0.001) were observed between AMH at all ages and total follicles or viable COCs at 365 days. However, correlations were weak to moderate when AMH was determined between 0 and 280 days, and strong when determined after 308 days. There was no correlation (P > 0.36) between AMH at any age and embryo rate. Circulating AMH before 196 days was not (P > 0.05) correlated with embryo yield, while AMH between 196 and 308 days was weakly (P < 0.05) correlated with embryo yield. Conversely, AMH at 365 days had a moderate correlation with embryo yield (P < 0.01). For further analysis, heifers were categorized using quartiles into low (Q1), intermediate (Q2 and Q3), and high (Q4) based on circulating AMH at each age. Outcomes obtained after IVEP at 365 days were then compared among heifers based on the age specific AMH class. As expected, total follicles, viable COCs, and embryo yield increased (P < 0.05) as heifer AMH class, determined at 365 days, increased. For example, embryo yield was greater (P < 0.05) for high (6.9 ± 1.4) than intermediate (3.8 ± 0.7) heifers, which in turn was greater than for low (2.1 ± 0.5) heifers. These distinctive differences in IVEP outcomes between AMH classes were consistently observed when AMH class was determined at 224 days or later, but not before 224 days. In conclusion, these results indicate that circulating AMH can identify donors with markedly different IVEP outcomes at 365 days, when AMH is determined after ~200 days coincident with the age at which circulating AMH stabilises.