雌二醇和孕酮对小鼠卵母细胞体外成熟的影响

目的研究雌二醇（E2）、孕酮（P4）对昆明小鼠卵母细胞体外成熟的影响。方法小鼠经注射孕马血清促性腺激素（PMSG）后48 h,摘取卵巢获得未成熟卵母细胞,分别在单独含不同浓度的E2或P4的成熟液中,或在同时含有不同浓度E2和P4的成熟液中,进行体外成熟,并对经过E2和P4处理成熟的卵母细胞进行体外受精。结果经15-16 h的成熟培养,各E2处理组的卵母细胞第一极体排出率虽然均略高于对照组,但它们之间无显著差异;各组卵母细胞体外受精48 h后,1000 ng/mL E2处理组的卵裂率显著低于其他各处理组和对照组,但各组的囊胚率之间无显著差异。各P4处理组的极体率和卵裂率,与对照组相比无显著差异,但是各处理组的囊胚率均极显著低于与对照组;两种激素协同处理组中[1000 ng/mL E2＋1000 ng/mL P4]组的极体率显著高于其他各处理组;而与对照组的极体率差异不显著。结论P4对小鼠卵母细胞的后期发育能力有一定的抑制作用,而E2却对小鼠卵母细胞的成熟及其发育潜力无明显作用。     

成熟培养液中胎牛血清添加量对山羊卵母细胞体外培养成熟的影响

本研究以屠宰奶山羊的新鲜卵巢为材料,回收可培养卵丘细胞-卵母细胞复合体(COC)。将可培养COC置于M199+FBS+100 IU/mL FSH+100 IU/mL LH培养微滴中,在5%CO2、95%空气、饱和湿度的CO2培养箱中39℃下培养。进行二因子三水平设计,比较基础培养液中添加FBS体积分数为0%、10%和15%时,及培养时间16 h、24 h、26 h的成熟率。结果表明:不添加FBS组的成熟率极显著(P0.01)低于其他两组,而10%FBS组与15%FBS组差异不显著(P0.05);体外培养16 h与培养24 h、26 h的卵母细胞成熟率分别为67.6%与81.7%、81.7%,差异极显著(P0.01),而后二者间未表现差异。     

左归丸促进小鼠未成熟卵母细胞体外核成熟的实验研究

目的：研究左归丸对小鼠未成熟卵母细胞体外核成熟的影响。方法：制备左归丸含药血清,将生发泡（germinal vesicle,GV）期卵母细胞分别在不同采血时间获取的左归丸含药血清培养液中进行体外培养,观察左归丸含药血清对生发泡破裂（germinal vesicle breakdown,GVBD）和第一极体（the first polar body,PB1）排出的时效关系。结果：药物血清组卵母细胞GVBD的发生率高于正常血清组和对照组,于培养后4h差异最显著（P〈0.01）;药物血清组卵母细胞PB1的发生率高于正常血清组和对照组,于培养后18h差异最显著（P〈0.01）。结论：2～2.5h左归丸含药血清对未成熟卵母细胞体外核成熟具有明显促进作用。     

卵巢运输温度及卵母细胞促成熟因子对山羊卵母细胞体外成熟和体外受精的影响

探讨山羊卵母细胞体外成熟培养的影响因素,为优化山羊体外受精程序奠定基础。比较从屠宰场采摘的山羊卵巢运输温度和体外培养促成熟因子对卵母细胞体外成熟培养和体外受精效果的影响。结果表明,在运输温度接近室温(25±2)℃时的卵母细胞成熟率显著高于接近体温(36±2)℃时的运输温度(成熟率分别为53.8%,35.0%,P0.01),两种运输温度的卵巢卵母细胞成熟培养后体外受精率无显著差异(分别为37.9%,36.6%,P0.05)。与在体外成熟基础培养液(M1:M199 media+1μg/mL E2+10μg/mL FSH+10μg/mL LH+20%EGS)中进行成熟培养相比,在基础培养液中仅添加20 ng/mL EGF(M2)和另外添加10%GFF(M3)进行体外成熟培养的卵母细胞成熟率均有明显提高,其中成熟率在M1为53.8%,极显著低于M2的69.5%和M3的72.6%,P0.01;M2和M3间差异不显著;卵母细胞成熟培养后体外受精率在三者间无明显差异分别为37.9%,39.5%和40.6%,P0.05。山羊体外受精时从屠宰场采摘的卵巢宜在室温条件下进行运输,在体外成熟培养体系中加入EGF和GFF均可有效促进山羊卵母细胞的体外成熟,但EGF起关键作用。     

小鼠卵母细胞体外成熟、体外受精的效果观察

目的　研究不同培养条件对小鼠卵母细胞体外成熟及体外受精率的影响。方法　小鼠卵母细胞分别在含有FSH、BSA和胰岛素的培养液中体外成熟,在Whitten 氏液中体外受精,比较体外成熟率、体外受精率。结果　1- 裸卵(DO) 的体外成熟率、体外受精率(81-4% ,31-0 % ) 均高于卵丘卵母细胞复合体(COC)(48-6 % ,27-1% ) 。2- 在培养液中添加FSH、胰岛素和BSA,卵母细胞的体外成熟率为77-9 % ,82-3% 、60-7% ;体外受精率为77-2 % 、72-6 % 、26-7% ;2 - 细胞率为49-2 % 、34-2 % 、10-0% 。胰岛素组的卵母细胞IVM 率最高,但IVF率、2 - 细胞率低于FSH 组。3- 添加BSA的两组的体外受精率只有26-7 % 、25-8 % ,显著低于其他组,其体外成熟率也较添加FSH 和胰岛素的组成。4- 排出第一极体(PbI) 的卵母细胞的体外受精率和2 - 细胞率(85-9 % ,22-4% ) 均高于GV期卵母细胞(71-1 % ,12-9 % ) 。结论　1- 卵丘卵母细胞(COC) 较裸卵(DO) 的体外成熟率、体外受精率都低,差异显著(P成熟< 0-01;P受精< 0-05) 。2-FSH 和胰岛素均能提高小鼠卵母细胞的体外成熟率、体外受精率。3-BSA可以降低小鼠卵母细胞体外受精率,差异极显著。4-GV 期卵母细胞的体外受精率显著低于体外培养的排出第一极体的卵母细胞(P2 - cell < 0-05,P受精<0-05)     

原癌基因c-myb在体外孕酮诱导小鼠卵母细胞成熟中的作用

目的：本文采用体外培养技术观察原癌基因c-myb对孕酮诱导的生发泡（GV）期小鼠裸卵体外成熟的影响。方法：建立小鼠裸卵体外培养模型,用不同浓度反义C-myb寡脱氧核苷酸（c-myb ASODNs）与GV期小鼠裸卵共孵育观察其对孕酮诱导的小鼠裸卵体外成熟的影响并探讨其机制。结果：在M199培养液中体外培养GV期小鼠裸卵24h,10μmol／L孕酮组与5μmol／L孕酮组比较有显著性差别（2 h GVBD％ P〈0.05,8 h PBI％ P〈0.05）．与20μmol／L孕酮组比较无显著性差别。10μmol／L c-myb AFODNs能抑制孕酮（10μmol／L）诱导的小鼠裸卵体外成熟（2 h GVBD％ P〈0.05,8 h PBI％ P〈0.01）。1×10^-4μmol／L dbcAMP、10μg／ml肝素钠可分别单独抑制孕酮诱导的GV期小鼠卵母细胞体外成熟（2 h GVBD％均P〈0.01,8 h PBI％均P〈0.01）．也可和反义c-myb ODN协同抑制孕酮诱导的卵母细胞体外成熟（2 h GVBD％均P〈0.01,8 h PBI％均P〈0.01）。结论：孕酮、原癌基因c-myb和cAMP、Ca^2＋参与了GV期小鼠卵母细胞的体外成熟,孕酮、cAMP和Ca^2＋调控卵母细胞成熟的机理可能与原癌基因c-myb表达有关。     

不同激素和注射方式对家猫超排效果的比较

比较了PMSG／hCG和FSH／hCG两种方案以及PMSG的不同剂量和注射方式对家猫的超排效果的影响。用100IU的PMSG超排家猫所得到的排卵点数及平均每只猫获得的卵数显著低于200IU处理组或300IU处理组（P＜0．05）,但200IU处理组与300IU处理组之间的超排效果也无显著差异（P＞0．05）;用皮下注射200IU的PMSG或用肌肉注射200IU的PMSG对超排效果无差异（P＞0．05）;用200IU PMSG／200IU hCG和1.5mg FSH/200IU hCG两种方案对家猫超排,发现不论是每只猫的排卵点数、卵子获得数,还是卵子的第一极体排放率都没有显著差异（P＞0．05）。实验说明,PMSG的注射方式不影响对家猫的超排效果,用200IU的PMSG超排家猫是较适合的剂量,FSH和PMSG都可用于家猫的超排,但PMSG使用更为方便。     

不同剂量孕马血清促性腺激素超排处理对家兔卵巢组织形态和胚胎发育的影响

为了研究不同剂量的孕马血清促性腺激素（PMSG）对家兔（Oryctolagus cuniculus f. domesticus）超排后,卵巢组织形态和PMSG对早期胚胎体外发育的影响。将24只家兔分为对照组、50 IU、70 IU和90 IU组,每组6只,对照组不做处理,后3组分别注射50 IU、70 IU和90 IU PMSG和定量100 IU人绒毛膜促性腺激素（HCG）对家兔进行超排处理。解剖后测定卵巢形态和组织参数。利用注射器抽取5ml冲卵液,分别从左右输卵管冲取胚胎至培养皿中,转至细胞培养室对胚胎进行体外培养观察。结果显示,PMSG处理组与对照组相比,随着PMSG注射剂量的增大,家兔卵巢重及宽度和厚度均极显著增大（P<0.01）,卵巢长度显著增长（P<0.05）,卵巢表面充血,卵泡数增多;另外,随PMSG注射剂量的增大,次级卵泡及其卵母细胞直径、三级卵泡直径均呈减小趋势（P <0.01）,三级卵泡中卵母细胞直径呈增大趋势,与对照组相比差异显著（P <0.05）;三级卵泡的直径和卵泡的优势化率,70 IU组显著高于对照组及50 IU和90 IU组（P &l...     

高尔基体对小鼠卵母细胞体外发育进程的影响

目的初步探讨高尔基体在小鼠卵母细胞体外发育进程中的作用。方法布雷菲德菌素A（Brefeldin A,BFA）处理小鼠未成熟,成熟卵母细胞,利用特异性标记物阻COP标记高尔基体。激光扫描共聚焦显微镜观察BFA处理对高尔基体产生的影响;同时。观察并比较不同处理组小鼠未成熟／成熟卵母细胞的体外成熟率、孤雌激活率、体外受精率及2-细胞率。结果GV期卵母细胞经BFA处理后,高尔基体的形态和分布发生明显改变。其体外成熟率（2．5％）与对照组（70．4％）比较统计学差异显著（P〈0．001）;洗掉BFA后,其体外成熟率（67．2％）与对照组无统计学差异（P〉0．05）。另外,成熟卵母细胞经BFA处理后。其体外受精率及2．细胞率均与对照组差异无统计学意义（P〉0．05）。结论小鼠卵母细胞体外成熟的正常进行需要高尔基体主导的膜运输。而体外受精和受精卵卵裂过程中不需要功能性的高尔基体。     

卵泡内环境对猪卵泡卵体外成熟和发育的影响

研究卵泡内环境对猪卵母细胞体外成熟、受精及受精卵体外发育的影响。主要结果如下：直径≥5mm、4－4.9mm、3－3.9mm和2－2.9mm的卵泡卵母细胞体外成熟率分别为90.5%、89.7%、85.4%和67.4%,体外受精后,卵母细胞的发育能力随卵泡直径的增大而增强,直径≥5mm和4－4.9mm卵泡卵的2－细胞、3－4－细胞发育率显著高于直径2－2.9mm的卵泡卵（P＜0.05或0.01）。体外成熟培养36h、42h和48h,直径2－2.9mm卵泡卵的体外成熟率,体外受精后的卵裂率差异不显著（P＞0.05）。在体外成熟培养液中添加5％或15％的不同直径卵泡的卵泡液,各组间卵母细胞的体外成熟率,受精卵的体外发育率均无显著差异,结果表明：卵泡大小对猪卵母细胞体外成熟、受精及受精卵体外发育有重要影响。     

Improved in vitro embryo development using in vivo matured oocytes from heifers superovulated with a controlled preovulatory LH surge

In bovine in vitro embryo production, the IVM step is rather successful with 80% of the oocytes reaching the MII stage. However, the extent to which the process limits the yield of viable embryos is still largely unknown. Therefore, we compared embryonic developmental capacity during IVC of IVF oocytes which had been matured in vitro with those matured in vivo. In vitro maturation was carried out for 22 h using oocytes (n = 417) obtained from 2- to 8-mm follicles of ovaries collected from a slaughterhouse in M199 with 10% fetal calf serum (FCS), 0.01 IU/mL LH, and 0.01 IU/mL FSH. In vivo matured oocytes (n = 219) were aspirated from preovulatory follicles in eCG/PG/anti-eCG-superovulated heifers 22 h after a fixed time GnRH-induced LH surge; endogenous release of the LH surge was suppressed by a Norgestomet ear implant. This system allowed for the synchronization of the in vitro and in vivo maturation processes and thus for simultaneous IVF of both groups of oocytes. The in vitro developmental potential of in vivo matured oocytes was twice as high (P < 0.01) as that of in vitro matured oocytes, with blastocyst formation and hatching rates 11 d after IVC of 49.3 +/- 6.1 (SEM; n = 10 heifers) vs 26.4 +/- 1.0% (n = 2 replicates), and 39.1 +/- 5.1% vs 20.6 +/- 1.4%, respectively. It is concluded that IVM is a major factor limiting in the in vitro production of viable embryos, although factors such as the lack of normal preovulatory development of IVM oocytes contributed to the observed differences.     

FSH priming improves oocyte maturation,but priming with FSH or hCG has no effect on subsequent embryonic development in an in vitro maturation program

AIM: To determine whether maturation and subsequent blastocyst development of in vitro matured oocytes can be improved by in vivo follicle stimulating hormone (FSH) or human chorionic gonadotrophin (hCG) priming, using a mouse model. EXPERIMENTAL DESIGN: Five groups of oocytes were used: in vivo control, in vitro matured (IVM) control, IVM after 24 h in vivo priming with FSH, IVM after 48 h in vivo priming with FSH and IVM after 16 h in vivo priming with hCG. In vitro fertilization (IVF) was performed on all groups.Oocyte maturation, fertilization, blastocyst development rates and blastocyst cell numbers were assessed for all groups. RESULTS: Significant improvement in oocyte maturation was observed in the two FSH priming groups compared with the IVM control group (P<0.005 and P<0.001, respectively). There were no significant differences in fertilization between all five groups. Blastocyst development was significantly higher in the in vivo control compared to the IVM groups (P<0.001). No significant differences were observed in blastocyst cell numbers among all five groups. CONCLUSIONS: While FSH priming improves the maturation rate of IVM oocytes, FSH or hCG priming does not improve development to the blastocyst stage.     

Effect of cysteamine during in vitro maturation on buffalo embryo development

The purpose of this study was to evaluate whether the addition of cysteamine during in vitro maturation (IVM) of buffalo oocytes enhances embryo development. Cumulus-oocyte complexes (COC) from slaughterhouse ovaries were matured in vitro in TCM 199 supplemented with 10% fetal calf serum (FCS), 0.5 microg mL(-1) FSH, 5 microg mL(-1) LH, 1 microg mL(-1) 17 beta estradiol and 0 (control), 50, 100 or 200 micromol L(-1) of cysteamine for 24 hours. The matured oocytes then were fertilized and cultured for 7 days. No beneficial effect on maturation and cleavage rate was related to the addition of cysteamine. However, the percentage of embryos that developed to compact morula and blastocyst stage was significantly higher (P < or = 0.01) for oocytes matured in medium containing 50 micromol L(-1) of cysteamine than it was for oocytes matured with 0, 100 and 200 micromol L(-1) cysteamine (22.6% vs 14.9%, 15.7% and 13% respectively); moreover, the addition of 50 micromol L(-1) of cysteamine during IVM significantly (P < or = 0.01) increased the proportion of transferable quality (Grades 1 and 2) embryos (19.3% vs 11.3%, 11.6% and 11.2% respectively). The present study showed that adding a thiol compound (such as cysteamine) to the IVM medium improves buffalo in vitro embryo production (IVEP) efficiency, which so far has been unsatisfactory.     

Gonadotropin exposure,salt storage and storage duration affect penetration of domestic cat oocytes by homologous spermatozoa

Salt-stored domestic cat oocytes are routinely used to study sperm function in domestic and nondomestic felids. Our objectives were to assess the effects of in vitro maturation (IVM), salt storage and storage duration on penetration of domestic cat oocytes by homologous spermatozoa. In Experiment 1, domestic cat spermatozoa were coincubated with fresh immature oocytes, salt-stored (2-3 weeks) immature oocytes, or salt-stored (2-3 weeks) IVM oocytes matured in Minimum Essential Medium containing 0.1IU FSH and 0.1IU LH/ml (IVM1) or 0.5IU FSH and 2.2IULH/ml (IVM2). In Experiment 2, all oocytes were matured (IVM2) and inseminated fresh or after salt storage for 2-3 weeks, 2-3 months or 9 months. In Experiment 1, penetration of the outer zona pellucida (OZP) was greater (P<0.05) in salt-stored IVM2 oocytes than in salt-stored immature oocytes, whereas penetration of salt-stored IVM1 oocytes was intermediate (P>0.05). In Experiment 2, penetration of the OZP and inner zona pellucida (IZP) was higher (P<0.05) in fresh IVM2 oocytes than in salt-stored oocytes, and a higher (P<0.05) proportion of oocytes had IZP sperm after 2-3 weeks of storage than after 2-3 months. Penetration of the perivitelline space was higher (P<0.05) in fresh IVM2 oocytes than in oocytes stored for 2-3 weeks or 2-3 months. These results suggest that oocyte penetration is improved by IVM, but is impaired by exposure to salt-storage solution and prolonged storage duration.     

Superovulation and in vitro oocyte maturation in three species of mice (Mus musculus, Mus spretus and Mus spicilegus)

Mouse oocytes can be obtained via superovulation or using in vitro maturation although several factors, including genetic background, may affect response. Our previous studies have identified various mouse species as models to understand the role of sexual selection on the evolution of sperm traits and function. In order to do comparative studies of sperm-oocyte interaction, we sought reliable methods for oocyte superovulation and in vitro maturation in mature females of three mouse species (genus Mus). When 5IU pregnant mare's serum gonadotrophin (PMSG) and 5IU human chorionic gonadotrophin (hCG) were injected 48h apart, and oocytes collected 14h post-hCG, good responses were obtained in Mus musculus (18+/-1.3oocytes/female; mean+/-S.E.M.) and Mus spretus (12+/-0.8), but no ovulation was seen in Mus spicilegus. Changes in PMSG or hCG doses, or longer post-hCG intervals, did not improve results. Use of PMSG/luteinizing hormone (LH) resulted in good responses in M. musculus (19+/-1.2) and M. spretus (12+/-1.1) but not in M. spicilegus (5+/-0.9) with ovulation not increasing with higher LH doses. Follicular puncture 48h after PMSG followed by in vitro maturation led to a high oocyte yield in the three species (M. musculus, 23+/-0.9; M. spretus, 17+/-1.1; M. spicilegus, 10+/-0.9) with a consistently high maturation rates. In vitro fertilization of both superovulated and in vitro matured oocytes resulted in a high proportion of fertilization (range: 83-87%) in the three species. Thus, in vitro maturation led to high yields in all three species. These results will allow future studies on gamete interaction in these closely related species and the role of sexual selection in gamete compatibility.     

Capacity of adult and prepubertal mouse oocytes to undergo embryo development in the presence of cysteamine

The present study was carried out to study de novo glutathione (GSH) synthesis and to evaluate the effect of stimulating GSH synthesis during in vitro maturation (IVM) of adult and prepubertal mouse oocytes on the embryo developmental rate. Adult (8 weeks old) and prepubertal mice (24-26 days old) were primed with 5 IU of PMSG and oocytes were retrieved from the ovary 48 hr later for IVM. After IVM (18 hr) Cumulus oocyte complexes (COC) were in vitro fertilized (IVF) and in vitro culture (IVC) in order to observe embryo development. The IVM medium was supplemented with: 0, 25, 50, 100, or 200 microM of cysteamine. To study the novo GSH synthesis, 5 mM BSO was added during IVM of adult or prepubertal oocyte. Developmental rates up to blastocyst were recorded for each group. Experiments also included a group of ovulated oocytes (in vivo matured) after priming with PMSG and HCG. After IVM of adult mice oocytes, an improvement was observed on embryo development in all the supplemented groups when compared with the untreated group (P < 0.05). No differences were observed in blastocyst rate among IVM oocytes with cysteamine and ovulated oocytes. Prepubertal IVM mouse oocytes had a lower cleavage rate compared with ovulated oocytes (P < 0.05). Cysteamine failed to improve prepubertal oocytes developmental rates (P > 0,05). 2-cell embryos, coming from IVM prepubertal oocytes and ovulated oocytes had the same preimplantation developmental rate up to the blastocyst stage. In prepubertal, and adult oocytes an inhibition of embryo development was observed when buthionine sulfoximide (BSO), a specific inhibitor of the gamma-glutamylcysteine synthetase, was added during oocyte maturation (P < 0.01). In conclusion, an improvement in mouse embryo development was observed when cysteamine was added to the IVM medium of adult mice oocytes. In prepubertal oocytes cysteamine addition during oocyte maturation failed to improve embryo developmental rates. The presence of BSO lowered or completely blocked blastocyst development. This proves that, de novo GSH synthesis during oocyte maturation of adult and prepubertal oocytes undoubtedly plays an important role in embryo development. The improvement on oocyte competence observed in adult mice oocytes is probably related to intracellular GSH synthesis stimulated by cysteamine. Nevertheless the reason why cysteamine failed to improve prepubertal oocytes competence remains as an open question.     

Influence of cysteamine supplementation and culture in portable dry-incubator on the in vitro maturation, fertilization and subsequent development of mouse oocytes

The need to transport oocytes and embryos between two laboratories have prompted us to evaluate the effects of in vitro maturation of immature mouse oocytes in a CO2-deficient dry heat portable incubator and subsequent in vitro development of these fertilized mouse oocytes in a standard CO2 incubator. In addition, the effects of cysteamine supplementation on maturation rate and embryonic development during in vitro maturation (IVM) and culture of embryos in the portable incubator were also investigated. Germinal vesicle stage mouse oocytes, recovered at 40-h post-FSH from 6- to 8-week-old C57BL/6xCBA F1 healthy female mice, were matured in vitro in a modified TCM-199 supplemented with or without 100 microM cysteamine in a standard incubator (5% CO2; 37 degrees C) or cultured in a CO2-deficient dry heat portable incubator for 5 h at 37 degrees C and thereafter transferred to a standard incubator for further culture. The addition of cysteamine in the IVM medium significantly improved maturation rates of the GV mouse oocytes to metaphase II stage. However, cysteamine supplementation in the culture medium did not significantly improve fertilization and blastocyst formation rates of IVM and ovulated oocytes, and in vivo-derived zygotes. Culture conditions in a CO2-deficient dry heat portable incubator did not adversely affect the developmental competence of in vivo-derived zygotes and in vitro matured mouse oocytes after IVF or parthenogenetic activation. Cysteamine supplement in the IVM medium could enhance nuclear maturation of these immature oocytes during shipment.     

Meiotic competence of bovine fetal oocytes following in vitro maturation

The in vitro ability between fetal and cow oocytes to resume meiosis and progression to metaphase-II (M-II) was compared. Cumulus oocyte complexes (COCs) were harvested from 2 to 6 mm follicles from ovaries of 7.5 month to term fetuses and adult cows. Cumulus cells were removed using 3 mg/ml hyaluronidase and repeated pipetting. Denuded oocytes were fixed in 3% glutaraldehyde, stained with DAPI and evaluated under fluorescent microscopy for nuclear status before in vitro maturation (IVM). COCs from fetal and adult ovaries were also matured in 200 microl droplets of medium 199 supplemented with 10 microg/ml FSH, 10/ml LH, 1.5 microg/ml estradiol, 75 microg/ml streptomycin, 100 IU/ml penicillin, 10 mM hepes and 10% FBS for 24 h at 39 degrees C and 5% CO(2). Matured oocytes were fixed, stained and evaluated as explained above for nuclear status namely stage of germinal vesicle (GV) development and subsequent meiotic competence. Data were analyzed using chi-square analysis. The majority of fetal oocytes (P<0.05) before IVM were at GV stages GV-I (27.7%), GV-II (37.6%) and GV-V (22.8%) compared to cow oocytes, which were at GV stages IV (28.3%) and V (46.7%). After IVM, fewer fetal oocytes were at earlier stages of GV development and majority (P<0.05) were at GV-V (24.0%), premetaphase (17.4%) and metaphase-I (M-I: 7.2%) stages. However, after IVM, more cow oocytes matured to M-II than did fetal oocytes (93.7% versus 26.9%; P<0.05). In conclusion, fetal oocytes do not mature in vitro as well as cow oocytes. Our findings suggest that the low meiotic competence of fetal oocytes can be attributed to their being at earlier stages of GV development before IVM.