In vivo oocyte recovery and in vitro embryo production from bovine donors aspirated at different frequencies or following FSH treatment

The effects of frequency of follicular aspiration and treatment of donor cattle with FSH on in vivo oocyte recovery and in vitro embryo production were studied. Simmental heifers (n = 24) formed 8 replicates of 3 treatments in which oocyte donors were aspirated 1) once a week, 2) twice a week, or 3) once a week following treatment with FSH for 3 d prior to aspiration. Oocytes were graded, washed, matured for 20 to 24 h and then inseminated with frozen/thawed semen from a single sire, followed by co-culture on granulosa cell layers. Embryo development was observed until Day 7 after insemination. Significantly fewer follicles per heifer per week were counted (14.7 ± 2.3 vs 27.4 ± 3.1 vs 23.1 ± 2.8) and aspirated (12.0 ± 2.0 vs 21.8 ± 2.7 vs 20.1 ± 2.6) in heifers on the once-weekly than twice-weekly aspiration treatment (P