In vitro embryos production of oocytes selected based on follicular size and by brilliant cresyl blue staining

Abstract

We evaluated the competence of bovine oocytes via morphological selection associated with follicular diameter and by brilliant cresyl blue (BCB) staining, in order to improve oocyte selection and the efficiency of in vitro embryo production. Follicles with small (2 < 4 mm), large (4–8 mm) or mixed (2–8 mm) diameters were aspirated from slaughterhouse ovaries. Next, the morphologically categorized oocytes were stained and evaluated with 26 ?M of BCB (90 min), followed by an assessment of in vitro maturation (MII) and blastocyst production. Oocytes from the large (61.1 ± 3.9%) and mixed (52.9 ± 4.6%) follicular groups showed comparable (p > 0,05) BCB+ rates, but both differed (p < 0.05) as compared to the small-diameter group (41.0 ± 4.5%). Between the BCB+ and BCB – oocytes, there was no difference (p > 0,05) in MII rate in the mixed (respectively 86.7 ± 3.4 and 75.8 ± 2.2), large (respectively 89.4 ± 2.6 and 79.7 ± 2.3) and small (respectively 76.7 ± 2.9 and 67.2 ± 2.5) diameter groups. Comparing BCB (+ and -) oocytes, we observed (p > 0,05) no change in the percentage of embryos in the large group (respectively 67.3 ± 3.3 and 53.5 ± 5.8) and in the small group (respectively 43.8 ± 5.3 and 33.9 ± 2.2), but there was a difference (p < 0.05) in the mixed group (respectively 57.8 ± 3.9 and 39.6 ± 7.5). Furthermore, when we compared between follicular groups, the BCB+/large-diameter group (61.1 ± 3.9%) had a significant higher percentage of embryos (p < 0.05) than the small-diameter BCB+ (43.8 ± 5.3) groups. To conclude, selection procedures that use follicle size and/or BCB staining may be used as an additional tool to improve the in vitro production of embryos.