Transvaginal follicular aspiration and embryo development in superstimulated early postpartum beef cows and subsequent fertility after artificial insemination

This study was conducted to investigate in early postpartum suckled beef cows with and without FSH pre-stimulation: (i) the influence of the postpartum period on the number and quality of oocytes recovered by ovum pick-up (OPU), (ii) the overall efficiency of the OPU/IVP embryos from days 30 to 80 postpartum and (iii) if repeated OPU negatively affect fertility following a fixed-time artificial insemination protocol. After parturition suckled Angus cows (n = 30) were divided in three groups (n = 10 group(-1)). All cows were anestrous at the commencement of experimental treatments (30.0 +/- 3.2 days postpartum, mean +/- SD; range 25-34 days). Group 1 treatments included: dominant follicle ablation (DFA), FSH treatment and OPU procedure 5 days after DFA. A total of 9 mg FSH (Ovagen) was administered s.c. once a day over 2 days at equal doses (4.5 + 4.5mg). For fertility test the cows received an intravaginal progesterone treatment from Days 78 to 86 postpartum and were fixed-time artificially inseminated (FTAI) at 56 and 72 h after device removal. Group 2: as cited for Group 1 with no FSH treatment. In both groups, OPU was repeated four times (Days 35, 49, 63 and 77 postpartum) and the collected oocytes classified as viable were in vitro matured, fertilized and presumptive embryos cultured for 8 days. Group 3 (Control FTAI): cows that had not previously aspirations were FTAI as Groups 1 and 2. Pregnancy was diagnosed by means ultrasonography 39 days after FTAI. The numbers (mean +/- SEM) of follicles visible and aspirated at the time of OPU in FSH-treated cows were greater (P < 0.05) than in non-treated cows (10.6 +/- 0.6 and 8.4 +/- 0.4 vs. 8.0 +/- 0.5 and 4.6 +/- 0.3, respectively). Following FSH treatment, the number (mean +/- SEM) of recovered oocytes per cow per OPU session and percentage of viable oocytes were greater in the treated (P < 0.05) than in non-treated animals (3.0 +/- 0.1 and 39.5% vs. 1.5 +/- 0.1 and 30.0%). The cleavage and embryo development rates were similar (P > 0.05) for both groups (14.8 and 6.4% vs. 16.6 and 5.5%). After FTAI the pregnancy rates were not different (P > 0.05) among groups (70, 60 and 90% for Groups 1, 2 and 3, respectively). We can conclude that (1) FSH-treated suckled postpartum cows can be a source of oocytes for in vitro fertilization and (2) repeated DFA/OPU applied during postpartum period did not affect the subsequent fertility following FTAI.