Effect of repeated eCG treatments and ovum pick-up on ovarian response and oocyte recovery during early pregnancy in suckling beef cows

This study was designed to evaluate in suckling early pregnant beef cows with and without eCG-pre-stimulation: (i) the influence of day gestation (from 40 to 101 days) and the consecutive eCG treatments on the follicular growth induced by means of ultrasound-guided transvaginal follicle ablation (FA; all follicles≥5mm) and the number and quality oocytes recovered by ovum pick-up (OPU) and (ii) the possible effects of repeated hormonal stimulation and FA/OPU on pregnancy outcome. Twelve suckling early pregnant Angus cows (40 days post fixed-time artificial insemination) were randomly assigned to each of two groups (n=6group⁻¹). Group 1 treatments included: FA (Day 0), eCG (1600IU; Day 1) and OPU (Day 5). Group 2: as cited Group 1 with no eCG treatment. In both groups, OPU was repeated five times (Days 45, 59, 73, 87 and 101 of gestation). The numbers (mean±SEM) of class II (5–9mm; 4.3±0.9) and class III (≥10mm; 2.5±0.4) follicles visualized per cow per OPU session in eCG-treated cows were greater (P<0.05) than for non-treated cows (0.9±0.1 and 0.9±0.1, respectively). In contrast, the number (mean±SEM) of class I (<5mm) follicles per cow per OPU session was lower for cows with eCG treatment (2.8±0.4) than for non-treated cows (5.7±0.5). The mean number of aspirated follicles was not significantly different (P<0.05) between eCG-treated cows and non-treated cows at 45 and 59 days of pregnancy. However, the mean number of aspirated follicles was greater (P=0.03) in eCG-treated cows than non-treated cows from 73 day of pregnancy onwards. The numbers (mean±SEM) of recovered oocytes and viable oocytes/cow/session were greater (P<0.05) for eCG-treated cows (2.2±0.2 and 1.6±0.4, respectively) than for non-treated cows (1.0±0.2 and 0.9±0.2, respectively). No donor pregnancies were lost either during or following OPU procedure. We can conclude that (1) eCG-treated pregnant suckled cows can be a source of oocytes for IVF at least to 100 days of gestation and (2) repeated FA/eCG treatment/OPU procedures did not affect the pregnancy outcome.