Pre-ovum pick up (OPU) dominant follicle (df) ablation: effect on in vitro gyr (Bos taurus indicus) embryo production (IVP)

The objective was to evaluate the effect of ablation of dominant follicle three days before ovum pick up (OPU) in lactating Gyr donors, considering oocyte yield and vitro embryo production (IVP). We also evaluated period of the year, body condition score and days in lactation (DEL). OPU procedures were performed 2 - 6 times, since 14 days post-partum at 21-day consecutive intervals. The trial was conducted at the EPAMIG research unit, Uberaba-MG. Twenty seven multiparous and 22 primiparous Gyr donors were randomly allocated in (DF-ablated, n=70) or not (control, n=128). Three days before OPU, cows were submitted to the ablation of DF as well as all follicles > 6 mm in diameter. From 198 OPU sessions, 6034 oocytes were obtained, being 3884 viable, resulting in 1114 blastocysts. Body condition scores (BCS) were attributed to donors on a scale from 1- very thin to 9- extremely obese. The mean number of viable oocytes recovered and blastocyst obtained after IVP per OPU session were 20.0 ± 10.6 and 5.70 ± 4.9, respectively. No effect on IVP yield traits due to parity, OPU session order or to the day post-partum the OPU was performed were detected. A one point increase in BCS resulted in an increase of 1.65 viable oocyte recovered at each OPU. Overall mean BCS was 4.35 ± 1.18 (3.0 – 7.0). Total and viable oocyte production were similar between DF-ablated (23.93±4.72 and 18.02±2.18) and control group (25.82±3.27 and 17.39±2.10), respectively. However, blastocyst production after IVP was superior (p<0.05) for the DF-ablated (5.65±1.02) compared to control (3.78±0.97). We conclude that DF ablation previous to OPU increases IVP efficiency. Also, lactating Gyr donors may be submitted to OPU as early as 14 d post-partum with 21 days of interval.