Antral Follicle Populations and Embryo Production – In Vitro and In Vivo – of B os indicus–taurus Donors from Weaning to Yearling Ages

Contents Interest in indicus–taurus cattle has been increasing, as these animals are likely to present the best characteristics of Z ebu and E uropean bovine breeds. The aim of this study was to compare the embryo production of indicus–taurus donors with high vs low antral follicle counts obtained by ovum pickup / in vitro production ( OPU / IVP ) and superovulation ( SOV )/embryo collection. Braford females at weaning age (3/8 N elore × 5/8 Hereford, n = 137, 9 ± 1 month old) were subjected to six serial ovarian ultrasonographs and were assigned to two groups according to the number of antral follicles ≥3 mm as follows: G‐High antral follicular count ( AFC , n = 20, mean ≥40 follicles) and G ‐Low AFC (n = 20, mean ≤10 follicles). When the females (n = 40) reached 24 months of age, they were subjected to both OPU / IVP and SOV /embryo collection. The average number of follicles remained highly stable throughout all of the ultrasound evaluations (range 0.90–0.92). The mean number of COC s recovered (36.90 ± 13.68 vs 5.80 ± 3.40) was higher (p < 0.05) for females with high AFC , resulting in higher (p < 0.05) numbers of total embryos among females with high vs low AFC (6.10 ± 4.51 vs 0.55 ± 0.83). The mean number of embryos per collection was also higher (p < 0.05) for G ‐ H igh vs G ‐ L ow (6.95 ± 5.34 vs 1.9 ± 2.13). We conclude that a single ultrasound performed at pre‐pubertal ages to count antral follicles can be used as a predictor of embryo production following IVP and SOV /embryo collection in indicus–taurus females.