TRANSVAGINAL ASPIRATION OF OOCYTES FROM HORMONE-TREATED PREGNANT BEEF-CATTLE FOR IN-VITRO FERTILIZATION

The ability to produce oocytes from genetically valuable, pregnant don ors in a safe, repeatable manner would broaden the application of in v itro fertilization (IVF) procedures for beef and dairy cattle. The obj ectives of this study were to evaluate two gonadotropin treatment sche dules for follicle stimulation of pregnant donor cattle and to determi ne the efficacy and safety of the repeated oocyte aspiration procedure from pregnant cattle. In Exp. 1, pregnant donors at 60 to 90 d of ges tation were randomly allotted to three treatment groups. Cows in Treat ment A received a total dose of 40 mg of FSH. Cows in Treatment B were administered a total of 20 mg of FSH, and females in Treatment C serv ed as pregnant vehicle-treated controls. A group of luteal phase cows received a total of 40 mg of FSH and served as nonpregnant controls (T reatment D). Ultrasound-guided transvaginal oocyte aspiration was perf ormed 12 h following the last FSH or saline injection. Following folli cle aspiration, oocytes were matured for 24 h and then entered a stand ard bovine IVF procedure. Experiment 2 was conducted to determine the repeatability of this procedure on first trimester cows. Cows in Exp. 2 were selected (after a 20-d recovery period) from each of the three pregnant treatment groups in Exp. 1 and each given 40 mg of FSH before a second oocyte aspiration procedure. The number of follicles aspirat ed per cow in treatment groups receiving the high FSH dose treatment ( 40 mg of FSH total dose) was not different (Treatment A, Treatment D, and cows in Exp. 2). The oocyte recovery rate for cows in Treatments A and D (also for cows in Exp. 2) given the high FSH dose was greater ( P < .05) than for cows in both Treatments B (low FSH dose) and C (no F SH). The percentage of viable oocytes recovered from pregnant donors i n Treatment A was greater (P < .05) than from similar pregnant females aspirated in Treatment B. This procedure proved to be effective and r epeatable for viable oocyte recovery and safe for pregnant donors, bec ause luteal function was maintained and no fetal loss resulted during pregnancy.