02283naa a2200301 a 450000100080000000500110000800800410001902200140006002400590007410000220013324500900015526000090024552013950025465000240164965000140167365000140168765000150170165000240171665000180174065300270175865300330178565300240181865300270184270000200186970000190188970000180190877300550192621436792022-06-02       2022    bl uuuu     u00u1 u    #d  a0378-43207 ahttps://doi.org/10.1016/j.anireprosci.2022.1070062DOI1 aPFEIFER, L. F. M.  aPostponing TAI in beef cows with small preovulatory follicles.h[electronic resource]  c2022  aThe aims of this study were (1) to establish an optimal cut-off point for evaluating the effect of the preovulatory follicle (POF) diameter in timed AI (TAI) programs, and (2) to evaluate the effect of postponing TAI in cows with smaller follicles on pregnancy per AI (P/AI). In Study 1, Nelore cows (n = 426) were subjected to an estradiol-progesterone (P4) based TAI protocol. The diameter of POF was measured at TAI, 48 h after P4 insert removal. From the ROC curves for determining the relationship between the POF diameter and pregnancy, the cut-off was 11 mm (P &lt 0.001). Cows with larger POF had greater (P &lt 0.05) P/AI (62.5%) than cows with smaller POF (34.8%). In Study 2, Nelore cows (n = 1257) were subjected to the same TAI protocol as in Study 1. Before TAI, cows were separated according to POF diameter in three groups: (1) Larger POF (LP, n = 873; POF ≥11 mm), (2) Smaller POF 0 h (SP0, n = 195; POF &lt11 mm), and (3) Smaller POF 24 h (SP24, n = 189; POF &lt11 mm). Cows in the LP and SP0 were TAI at 48 h and cows in the SP24 group were TAI at 72 h after P4 insert removal. Cows in the LP group had the greatest (P &lt 0.05) P/AI (60.25%), followed by cows in the SP24 group (41.8%), while cows in the SP0 group had the lowest P/AI (31.8%). In conclusion, cows with smaller follicles have lower P/AI, but postponing the TAI by 24 h in these cows increases P/AI.  aAnimal reproduction  aBeef cows  aOvulation  aOvulação  aReprodução Animal  aVaca de Corte  aDiâmetro do folículo  aFolículos pré-ovulatórios  aFollicular diameter  aPreovulatory follicles1 aGASPERIN, B. G.1 aCESTARO, J. P.1 aSCHNEIDER, A.  tAnimal Reproduction Sciencegv. 242, 107006, 2022.