The use of pre-pubertal calves as oocyte donors offers a considerable potential to increase the genetic gain lowering the generations interval, as well as increase the usage of bovine females with high genetic value. The objectives of this study were to analyze the effect of age and of the stimulatory treatment with gonadotropins in the follicular response, the recovery rate, quantity and quality of oocytes of the prepubertal Nelore (B. t. indicus) calves. Twelve Nelore prepubertal females were stimulated with gonadotrophin hormone and were submitted to ultrasound guided transvaginal oocyte recovery (OPU) at 10, 11 and 12 months of age. Before OPU the females were randomly distributed into three treatment groups (n=4), which consist of different protocols of ovarian super stimulation. For all treatments the animals on day zero (D0) received one intravaginal progesterone implant (CIDR-G®) and on D1, 2 mg of estradiol benzoate im (Estrogin®). The stimulatory treatment began on D6 according to the following treatments: T1-120 IU of FSH (Foltropin®), divided in 4 im injections with 12 hours interval; T2-120 IU of FSH in one sc application plus 300 IU of eCG (Folligon®) on D6; T3 - without stimulatory treatment (control). At D8 the CIDR-G®was removed and OPU was performed on D9. Among the 402 oocytes retrieved, 53 were denuded and measured (including the pellucid zone) where a mean diameter of 153.38 ± 8.06 mm was obtained. No significant difference was detected among treatments and among ages for the quantity of follicles > 3 mm, quantity of oocytes recovery and quantity of oocytes morphologically viable. The mean of recovery oocytes and viable oocytes for each treatment was T1- 11.08 (6.20) and 59.58% (25.80), T2 - 12.75 (8.04) and 66.02% (36.71), T3 - 9.66 (8.15) and 51.51% (30.69), respectively. The mean value of recovery rate was 78.70%. The use of FSH or FSH + eCG does not increase significantly the amount of follicles > 3 mm at the OPU moment, as well as the total and viable oocytes by 10, 11 and 12 months of age.
hormonal stimulation; pre-pubertal calf; oocyte; OPU; Zebu
