Repeatability of antral follicle counts and anti-Müllerian hormone and their associations determined at an unknown stage of follicular growth and an expected day of follicular wave emergence in dairy cows

The objectives were to determine (1) the repeatability of antral follicle counts (AFC) and anti-Müllerian hormone (AMH) concentrations at an unknown stage of follicular growth (FG) and at an expected day of follicular wave emergence (FWE) in dairy cows, and (2) the association between AFC and AMH at the above two stages. Transrectal ultrasound imaging of the ovaries and blood sample collection were performed on 91 lactating Holstein cows (33 primiparous, 58 multiparous) to determine AFC and serum concentrations of AMH at an unknown stage of FG (mean ± SEM; 14 ± 0.5 d postpartum) and an expected day of FWE (mean ± SEM; 73 ± 0.5 d postpartum, approximately 36 h after the 2nd GnRH of Ovsynch protocol). The AFC ranged from 10 to 53 (mean ± SEM; 26.1 ± 1.0) and 6 to 45 (mean ± SEM; 23.4 ± 1.0) at an unknown stage of FG and expected day of FWE, respectively (P = 0.02). Serum concentrations (pg/mL) of AMH ranged from 13.9 to 528.8 (mean ± SEM; 187.3 ± 13.1) and 38.2 to 774.1 (mean ± SEM; 218.7 ± 14.5) at an unknown stage of FG and expected day of FWE, respectively (P