Oocyte cytoplasmic evaluation is based on homogeneity and granular appearance. Our study investigated if a granular cytoplasm, highly heterogeneous, would affect oocyte competence in bovine. In two experiments, bovine cumulus–oocyte complexes (COCs) with homogeneous cytoplasm (control, CC) and granulated cytoplasm (granular, GC) were selected from a regular pool of COCs. Experiment 1 was performed with slaughterhouse ovaries, and Experiment 2 was carried out in Girolando COCs obtained from ovum pick-up. Granular oocytes had higher caspase 3 levels (66.17 ± 11.61 vs 172.08 ± 16.95, P < 0.01) and similar GAP junction activity (5.64 ± 0.45 vs 6.29 ± 0.29). ZAR1 relative mRNA amount was lower in granular oocytes (178.27 ± 151.63 vs 0.89 ± 0.89, P = 0.01) and no effect was detected for MATER, PPP2R1A, ENY2, IGF2R, and BMP15 genes. Despite molecular differences, no detrimental effect was detected on oocyte competence in GC oocytes. Cleavage (Experiment 1: 59.52 ± 7.21% vs 59.79 ± 6.10% and Experiment 2: 68.88 ± 4.82 vs 74.41 ± 5.89%) and blastocyst (Experiment 1: 29.28 ± 4.14% vs 23.15 ± 2.96% and Experiment 2: 21.11 ± 3.28% vs 21.02 ± 6.08%) rates were similar between CC and GC (Experiments 1 and 2, respectively). Post-transfer embryo development revealed that pregnancy (CC: 24.27 ± 9.70% vs GC: 26.31 ± 7.23%) and calving (23.68% vs 33.33%) rates and fetal growth were not affected by the presence of cytoplasmic granules. Our results demonstrated that oocytes with granular cytoplasm present equivalent efficiency for IVF and calf production compared with homogenous cytoplasm oocytes. This could be observed through similar cleavage, blastocyst rates, and fetal growth development. In addition to differences in oocyte gene expression related to oocyte quality, it seems not to affect oocyte developmental competence.

During fertilisation of a fully mature oocyte, the sperm intrinsic nuclear envelope (SINE) disappears soon after sperm-oocyte fusion. A new nuclear envelope appears around the decondensed sperm chromatin when the oocyte reaches telophase II. Whether the SINE persists or rapidly disappears after sperm entery into immature oocytes or fertilised eggs has been controversial. Nuclear envelopes have been demonstrated around the sperm chromatin, which cannot be decondensed within the ooplasm of these oocytes or eggs, but whether these envelopes are persisting SINEs or newly formed envelopes has been apoint of dispute. To resolve this issue, the fate of the germinal vesicle stage(GV oocytes) or fertilised eggs at the pronuclear stage(PN eggs). The SINEs disappeared quikly within these oocytes or eggs, like those within maturing or mature oocytes, suggesting that the envelops around the sperm chromatin must be newly formed after SINE breakdown. To obtain further evidence, a detergent-treated, SINE-free sperm nucleus was injected into a PN egg. A new envelope appeared around the still-condensed or partially decondensed sperm chromatin within 3h after injection. Thus, disassembly of the SINE within ooplasm, unlike that of nuclear envelopes of other cells at prophase, is independent of the cell cycle stage of the oocyte or egg, whereas the ability of the ooplasm to assemble the new envelope is restricted to certain periods of the cycle. i.e. early prophase and telophase during meiosis and interphase, periods when active M-phase Promoting factor (MPF) is absent from the ooplasm.