RÉSUMÉ
Objective. This study evaluated the effect of age and coasting period over oocyte quality and their posterior development under in vitro conditions from prepubertal Bos indicus crossbred donors. Material and methods. Donors females received a norgestomet implant and estradiol benzoate. Four days later a unique dosage of 150 IU of eCG was administered. Three coasting periods (24, 48, and 56 h) and four ages (3, 6, 10, and 12 months) were proved. All antral follicles were aspirated and an in vitro culture proceed was done. Results. 439 follicles were aspirated, of which 385 (87.7%) were 2-5 mm, 41 (9.33%) were 5-10 mm, and 13 (2.3%) were 10 mm. After aspiration, a total of 373 oocytes (84.9%) were recovered, finding differences (p<0.05) between averages of 6 (9.3) and 10 months old animals (32.3). 285 (76.4 %) recovered oocytes were subjected to in vitro process. Cleavage values were significantly higher (p<0.05) in 10 (27.1%) and 12 months animals (26.8%). Although the number of transferable embryos was low, there were differences between ages (p<0.05) obtaining a higher percentage in age 3 (12.6%). Conclusions. A coasting period higher than 24 h has a negative effect on oocyte quality. Some oocytes from 3 months old calves were competent for in vitro embryo development; however, higher numbers of embryos were produced from 10 and 12 months of age prepuber females, indicating they have higher competency in vitro.