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The aim of this study was to compare the conception rates to fixed-time artificial insemination (FTAI) and in vitro embryo production between Nelore cows with high or low antral follicle counts (AFC). First, multiparous Nelore cows (Bos indicus, n = 547, 40–60 days postpartum) were subjected to synchronization of ovulation. Randomly during their oestrous cycle (Day 0), cows received an intravaginal device containing 1.9 g of P4 (CIDR®) and 2 mg of oestradiol benzoate (Estrogin®), intramuscularly. At device removal (Day 8), cows received 500 µg of PGF2α (Ciosin®), 300 IU of eCG (Novormon®), and 1 mg of oestradiol cipionate (ECP®), intramusculary. All cows were inseminated 48 h after P4 device removal. Antral follicles = 3 mm were counted using an intravaginal microconvex transducer (Day 0), and cows were assigned to groups of high (G-High, = 25 follicles, n = 183), intermediate (G-Intermediate, 16–20 follicles, n = 183), or low AFC (G-Low, = 10 follicles, n = 181). In another study to compared the in vitro embryo production, Nelore cows (n = 66, 72–96 months) were subjected to ultrasound-guided follicular aspiration using an intravaginal microconvex array transducer (7.5 MHz). The COC were selected and cows were assigned to groups according to the oocyte production: G-High (n = 22, = 40 oocytes), G-Intermediate (n = 25, 18–25 oocytes), or G-Low (n = 19, = 7 oocytes). Previously tested semen from a single bull was used for IVF using a previously described protocol (Silva-Santos et al. 2014 Reprod. Domest. Anim. 49, 228–232). The oocyte and embryo production (viable embryo: grade I, II, III; vitrifiable embryo: grade I, II) were evaluated. The number of follicles was evaluated by Kruskal-Wallis, and the chi-square test was used for data on oocyte and embryo production (P = 0.05). The average follicular population was 30.7 ± 5.7 (G-High), 18.6 ± 1.64 (G-Intermediate), and 7.8 ± 2.4 follicles (G-Low; P 0.05). The total number of oocytes recovered were 1109 (G-High), 534 (G-Intermediate), and 101 (G-Low; P |