This study was designed to determine the efficiency of three different technics for staining bovine oocyte in the germinal vesicle (GV), metafase I (MI) and metafase II (MII) stages. In these stages, oocytes without cumulus cells were fixed in acetic acid:methanol (1:3) either on slides (FLL) or in petri dishes (FPL) and stained with 1% of lacmoid in phosphate buffered saline (PBS). Also, the oocytes were randomized divided in a third treatment, in which they were fixed on slides immersed in acetic acid:methanol (1:3) and stained with Giemsa (FLG). In the GV stage, the percentage of oocytes accurately identified in the FLL (93.5%) was significantly higher than in the FPL (53.1%; χ2=9.84; p=0.0017) and FLG (55.2%; χ2=9.03; p=0.0027) treatment groups. However, the proportion of oocytes in the MI and MII stages correctly stained with FLL technic (MI 41.7% and MII 41.9%) was statistically lower than that observed in the FPL (MI 90.0%, χ²=13.25; p=0.0003, and MII 92.8%, χ²=12.45; p=0.0004) and FLG (MI 83.3%, χ²=10.69; p=0.0011, and MII 89.7%, χ²=12.24; p=0.0005) treatment groups. With these results, it can be established that the efficiency of the technic to fix and to stain bovine oocyte depends on the nuclear maturation stage to be investigated.
oocyte; nuclear maturation; meiosis; bovine
