303 Effect of Semen Batches After Sexing on Production Efficiency of Bovine Embryos in Vitro

Abstract

Within an in vitro production system, bulls differ with respect to their semen potential in generating embryos when the variables of maternal effects are minimized (Marquant-le-Guienne and Humblot 1992 Ann. Zootech. 41, 361-370). We have tested the hypothesis that even with this variation among bulls, there is also an intra-bull variation among frozen sexed semen batches (Sexing Technologies, Navasota, TX, USA; personal communication) when used with IVF. In an embryo commercial production system, 5058 viable oocytes obtained by ovum pick-up with ultrasound from 193 Nelore cows (Bos indicus) over a 12-month period were matured in vitro for 24 h in TCM-199 (Gibco, Life Technologies, Carlsbad, CA, USA) containing 0.5 μg mL-1 FSH (Bioniche Animal Health, Belleville, Ontario, Canada), 50 μg mL-1 LH (Intervet, Boxmeer, the Netherlands) and 10% fetal bovine serum (Gibco). Mature oocytes were inseminated in vitro for 18 h in IVF-Talp medium (BSA-FAF 6 mg mL-1; 10 ng of heparin, Sigma, France), using 3 different batches (I, II, III) of frozen-thawed sexed semen from 4 bulls (A, B, C, D), separated with a Percoll gradient (45:90; Sigma, St-Quentin Fallavier, France). Putative zygotes surrounded in cumulus cells were transferred in CR2aa medium droplets (Rosenkrans and First 1994 J. Anim. Sci. 72, 434-437) with 3 mg mL-1 BSA-FV (Sigma) for 163 h in a humidified incubator at 39°C, with an atmosphere of 5% CO2 in air. Total number of oocytes, total number of blastocysts, and embryonic developmental rates for each bull and respective batch are reported in Table 1. The chi-square test was measured with a significance level of P < 0.05 and showed that there is difference between the batches used with respect to developmental rates of blastocysts. Therefore, there is intra-bull variation in the ability to produce in vitro embryos according to the batch of frozen sexed semen. Table 1.Viable oocytes (VO), total blastocysts (TB), and embryo development rate (%E) by bull and batch used in IVF