313 PRE-IN VITRO MATURATION WITH CYCLIC AMP AND CYCLIC GMP MODULATORS IMPROVES DEVELOPMENTAL COMPETENCE OF MOUSE OOCYTES

2015 ◽  
Vol 27 (1) ◽  
pp. 245 ◽  
Author(s):  
N. W. Santiquet ◽  
A. F. Greene ◽  
W. B. Schoolcraft ◽  
R. L. Krisher
Keyword(s):  
Embryo Development ◽  
In Vitro Maturation ◽  
Subsequent Development ◽  
Developmental Competence ◽  
Nuclear Maturation ◽  
Oocyte Developmental Competence ◽  
Oocyte Collection ◽  
Short Period

In vitro maturation (IVM) of cumulus-oocyte complexes (COC) results in oocytes with reduced quality and is still not as efficient as in vivo maturation in most species. One hypothesis that could explain the low developmental competence of oocytes following IVM is that the oocytes resume meiosis too quickly after being retrieved from the follicles. Studies in mice and bovine have shown that a short period of prematuration in the presence of cAMP modulators, before IVM, enhances oocyte developmental competence. Moreover, other studies have recently demonstrated that cGMP is also a crucial molecule involved in meiotic resumption. Here, our objective was to examine the effect of a cGMP modulator in combination with a cAMP modulator during a short period of prematuration on mouse oocyte nuclear maturation and subsequent embryo development following IVF. The COC were collected (6 replicates) from 2-month-old outbred CF1 mice 48 h after PMSG (5 IU) injection in the presence (pre-IVM) or absence (control) of cGMP and cAMP modulators. Pre-IVM COC (n = 184) were then placed in prematuration medium that also contained these cGMP and cAMP modulators. After 2 h, pre-IVM COC were washed and transferred to our in-house prepared, completely defined IVM medium (Paczkowski et al. 2014 Reprod.) for the remaining 16 h of culture; 10 oocytes per 50 µL drop under oil, at 37°C in 7.5% CO2 and 6.5% O2 due to the increased altitude at our location. Control COC (n = 161) were matured in the same IVM medium under identical conditions for 18 h, without prematuration. After IVM, oocytes were fixed for assessment of nuclear maturation, or fertilized and cultured in vitro and subsequent development (96 and 112 h) was recorded (Paczkowski et al. 2014 Reprod.). Results were analysed by ANOVA. A short 2-h prematuration period in the presence of cGMP and cAMP modulators had no impact on oocyte nuclear maturation to metaphase II after IVM or on embryo cleavage after IVF. However, pre-IVM treatment improved the developmental competence of the oocyte, as demonstrated by increased embryo development. More (P < 0.02) blastocysts (96 h of culture) and hatched blastocysts (112 h of culture) developed in the pre-IVM treatment compared to control (31.0 ± 3.4 v. 19.9 ± 3.2%; 31.5 ± 3.4 v. 19.9 ± 3.2%, respectively). In conclusion, a combination of cGMP and cAMP modulators during oocyte collection and a subsequent short pre-IVM improves oocyte developmental competence and could therefore be a potential tool to improve embryo yield following IVM.

scholarly journals Quercetin improves developmental competence of mouse oocytes by reducing oxidative stress during in vitro maturation

2018 ◽  
Vol 18 (1) ◽  
pp. 87-98
Author(s):  
Seyede Zahra Banihosseini ◽  
Marefat Ghaffari Novin ◽  
Hamid Nazarian ◽  
Abbas Piryaei ◽  
Siavash Parvardeh ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Embryo Development ◽  
In Vitro Maturation ◽  
Mature Oocyte ◽  
Developmental Competence ◽  
Nuclear Maturation ◽  
Mouse Oocytes ◽  
Blastocyst Rate ◽  
And Control

Abstract Quercetin is a natural flavonoid with strong antioxidant activity. In the present study, we evaluate the influence of different concentrations of quercetin (QT) on intracytoplasmic oxidative stress and glutathione (GSH) concentration, during in vitro maturation (IVM) and fertilization in mouse oocytes. IVM was carried out in the presence of control (QT0), 5 (QT5), 10 (QT10), and 20 (QT20) μg/mL of QT. Nuclear maturation, intracellular GSH and ROS content were evaluated following the IVM. In these oocytes, we subsequently evaluated the effect of QT supplementation on embryo development, including 2-cell, 8-cell, and blastocyst rate. The results of the present study showed that the supplementation of 10 μg/mL QT in maturation medium increased the number of MII oocytes. In addition, fertilization and blastocyst rate in QT10 treatment group were significantly higher in comparison to the other groups, and elevated the amount of intracellular GSH content compared to other QT concentrations and control groups. The intracellular ROS level was the lowest among oocytes matured in Q5 and Q10 treatment groups. This result suggested that quercetin dose-dependently improves nuclear maturation and embryo development, via reducing intracytoplasmic oxidative stress in mature oocyte.

127 L-Carnitine Supplementation During In Vitro Maturation Improves Developmental Competence of Canine Oocytes

2018 ◽  
Vol 30 (1) ◽  
pp. 203 ◽  
Author(s):  
A. Salama ◽  
M. Fathi ◽  
M. R. Badr ◽  
A. R. Moawad
Keyword(s):  
Embryo Development ◽  
In Vitro Maturation ◽  
Assisted Reproductive Technologies ◽  
Mammalian Species ◽  
Reproductive Technologies ◽  
Developmental Competence ◽  
Carnitine Supplementation ◽  
Cell Stage ◽  
Nuclear Maturation

In vitro embryo production (IVP) in the domestic bitch is important for conservation of endangered canids. Compared with various domestic animals, the development of assisted reproductive technologies (ART) in the dog has lagged behind, mainly due to the low percentage of oocytes that can reach metaphase II (MII) stage after in vitro maturation (IVM). Beneficial effects of l-carnitine (LC) on embryonic development in culture have been reported in many mammalian species; however, no studies have been conducted in dogs. The aim of the present study was to investigate the effect of LC supplementation during IVM of canine oocytes on nuclear maturation, fertilization status, and pre-implantation development following IVM/IVF. Cumulus-oocyte complexes (COC) were collected by slicing ovaries obtained from dogs (n = 20, 1 to 6 years of age) after ovariohysterectomy. The COC were subjected to IVM for 72 h in a medium (TCM-199) supplemented with LC at different concentrations (0.1, 0.3, 0.6, 1.0, or 2.0 mg mL−1) or without LC supplements (0 mg mL−1; control). Matured oocytes were fertilized in vitro with frozen–thawed spermatozoa, and presumptive zygotes were cultured in SOF medium for 7 days. Frequencies of nuclear maturation (72 h post-IVM), fertilization rates (18 h post-insemination), and embryo development (Days 2 to 5 post-insemination) were evaluated. Data were analysed by one-way ANOVA followed by Tukey’s multiple comparisons test. Supplementation of IVM medium with 0.3 or 0.6 mg mL−1 LC significantly improved (P ≤ 0.05) maturation (35.4% and 41.4%) and fertilization (21.3% and 25.8%) rates compared with the controls and with other LC-supplemented groups; values ranged from 20.1% to 25.0% for maturation and from 12.1% to 14.6% for fertilization. Cleavage (2- to 16-cell stages) was significantly higher (P ≤ 0.05) in the 0.6 mg mL−1 LC supplemented group than the 0.3 mg mL−1 supplemented group (16.3% v. 13.3%). These values were significantly higher (P ≤ 0.05) than those in other groups. Interestingly, 4.5% of IVM/IVF oocytes were developed to morula in 0.6 mg mL−1 LC supplemented group which was significantly higher (P ≤ 0.05) than those developed in the 0.3 mg mL−1 supplemented group (1.0%). No embryos developed beyond the 2- to 16-cell stage in the rest of the groups. In conclusion, l-carnitine supplementation during IVM is particularly efficient in improving nuclear maturation and pre-implantation embryo development of canine oocytes after IVF. These outcomes are important for the improvement of IVM conditions that can advance the efficiency of ART in dogs.

scholarly journals Effects of different oocyte retrieval and in vitro maturation systems on bovine embryo development and quality

Zygote ◽  
2014 ◽  
Vol 23 (3) ◽  
pp. 367-377 ◽  
Author(s):  
Sandra Milena Bernal ◽  
Julia Heinzmann ◽  
Doris Herrmann ◽  
Bernd Timmermann ◽  
Ulrich Baulain ◽  
...  
Keyword(s):  
Gene Expression ◽  
Embryo Development ◽  
Expression Profiles ◽  
Expression Patterns ◽  
Developmental Competence ◽  
Bovine Embryo ◽  
Global Methylation ◽  
Oocyte Developmental Competence

SummaryCyclic adenosine monophosphate (cAMP) modulators have been used to avoid spontaneous oocyte maturation and concomitantly improve oocyte developmental competence. The current work evaluated the effects of the addition of cAMP modulators forskolin, 3-isobutyl-1-methylxanthine (IBMX) and cilostamide during in vitro maturation on the quality and yields of blastocysts. The following experimental groups were evaluated: (i) slicing or (ii) aspiration and maturation in tissue culture medium (TCM)199 for 24 h (TCM24slicing and TCM24aspiration, respectively), (iii) aspiration and maturation in the presence of cAMP modulators for 30 h (cAMP30aspiration) and in vivo-produced blastocysts. In vitro-matured oocytes were fertilized and presumptive zygotes were cultured in vitro to assess embryo development. Cleavage, blastocyst formation, blastocyst cell number, mRNA abundance of selected genes and global methylation profiles were evaluated. Blastocyst rate/zygotes for the TCM24aspiration protocol was improved (32.2 ± 2.1%) compared with TCM24slicing and cAMP30aspiration (23.4 ± 1.2% and 23.3 ± 2.0%, respectively, P<0.05). No statistical differences were found for blastocyst cell numbers. The mRNA expression for the EGR1 gene was down-regulated eight-fold in blastocysts that had been produced in vitro compared with their in vivo counterparts. Gene expression profiles for IGF2R, SLC2A8, COX2, DNMT3B and PCK2 did not differ among experimental groups. Bovine testis satellite I and Bos taurus alpha satellite methylation profiles from cAMP30aspiration protocol-derived blastocysts were similar to patterns that were observed in their in vivo equivalents (P > 0.05), while those from the other groups were significantly elevated. It is concluded that retrieval, collection systems and addition of cAMP modulators can affect oocyte developmental competence, which is reflected not only in blastocyst rates but also in global DNA methylation and gene expression patterns.

Gene transcription and regulation of oocyte maturation

2004 ◽  
Vol 16 (2) ◽  
pp. 55 ◽  
Author(s):  
Karina F. Rodriguez ◽  
Charlotte E. Farin
Keyword(s):  
Oocyte Maturation ◽  
In Vitro Maturation ◽  
Transcriptional Control ◽  
Molecular Mechanisms ◽  
Developmental Competence ◽  
Developmental Potential ◽  
Oocyte Developmental Competence ◽  
Specific Factors

The developmental potential of an embryo is dependent on the developmental potential of the oocyte from which it originates. The process of oocyte maturation is critical for the efficient application of biotechnologies such as in vitro embryo production and mammalian cloning. However, the overall efficiency of in vitro maturation remains low because oocytes matured in vitro have a lower developmental competence than oocytes matured in vivo. Furthermore, oocytes that have been exposed to gonadotropins have greater developmental competence than oocytes matured in the absence of gonadotropins. By understanding the molecular mechanisms underlying gonadotropin-induced maturation, improvement in oocyte maturation technologies may be expected as procedures to manipulate specific factors involved in signalling for resumption of meiosis are identified. The present review will focus on transcriptional mechanisms underlying the maturation of mammalian oocytes in vitro, as well as on the acquisition of oocyte developmental competence. In addition, a working model for the transcriptional control of mammalian oocyte maturation is proposed.

scholarly journals Histone deacetylase inhibitor during in vitro maturation decreases developmental capacity of bovine oocytes

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0247518
Author(s):  
Thais Preisser Pontelo ◽  
Mauricio Machaim Franco ◽  
Taynan Stonoga Kawamoto ◽  
Felippe Manoel Costa Caixeta ◽  
Ligiane de Oliveira Leme ◽  
...  
Keyword(s):  
Embryo Development ◽  
In Vitro Maturation ◽  
Embryo Quality ◽  
Cumulus Cells ◽  
Developmental Competence ◽  
Nuclear Maturation ◽  
Deacetylase Inhibitor ◽  
Developmental Capacity ◽  
Bovine Oocytes

This study aimed to evaluate the effect of scriptaid during pre-maturation (PIVM) and/or maturation (IVM) on developmental competence of bovine oocytes. Cumulus-oocyte complexes (COCs) were submitted to PIVM for 6 h in the presence or absence of scriptaid. COCs were distributed into five groups: T1-IVM for 22 h, T2-PIVM for 6 h and IVM for 22 h, T3-PIVM with scriptaid for 6 h and IVM for 22 h, T4-PIVM for 6 h and IVM with scriptaid for 22 h, and T5-PIVM with scriptaid for 6 h and IVM with scriptaid for 22 h. Nuclear maturation, gene expression, cumulus cells (CCs) expansion, and embryo development and quality were evaluated. At the end of maturation, all groups presented the majority of oocytes in MII (P>0.05). Only HAT1 gene was differentially expressed (P<0.01) in oocytes with different treatments. Regarding embryo development at D7, T4 (23%) and T5 (18%) had lower blastocyst rate (P<0.05) than the other treatments (T1 = 35%, T2 = 37% and T3 = 32%). No effect was observed when scriptaid in PIVM was used in less competent oocytes (P>0.05). In conclusion, presence of scriptaid in PIVM and/or IVM did not improve developmental competence or embryo quality.

163 EFFECTS OF DIFFERENT IN VITRO MATURATION SYSTEMS ON EMBRYO DEVELOPMENT IN BOVINE PREPUBERTAL AND ADULT DONORS

2014 ◽  
Vol 26 (1) ◽  
pp. 195
Author(s):  
S. M. Bernal ◽  
J. Heinzmann ◽  
D. Herrmann ◽  
U. Baulain ◽  
A. Lucas-Hahn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Embryo Development ◽  
In Vitro Maturation ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Developmental Competence ◽  
In Vitro Production ◽  
Lactating Cows

Prepubertal bovine females have been suggested as a source of oocytes in order to accelerate genetic gain and decrease the generation interval. However, prepubertal oocytes have a lower developmental competence than their adult counterparts. In vitro maturation (IVM) systems using cyclic AMP (cAMP) regulators and 30-h culture have been suggested to improve blastocyst in vitro production rates from bovine oocytes (Albuz et al., 2010). The present study evaluated the effects of an addition of the cAMP modulators forskolin, 3-isobutyl-1-methylxanthine (IBMX), and cilostamide during extended IVM on blastocyst yields and gene expression in prepubertal and adult bovine females. Holstein-Friesian donors were submitted to ovum pick-up twice per week. Oocytes from groups of 12 animals, including lactating cows (>2 lactations) and prepubertal donors (6–10 months old) were used in the following treatment groups: TCM24 (24-h IVM, routine protocol/control), cAMP30 (2-h pre-IVM culture using forskolin-IBMX and 30-h IVM adding cilostamide), DMSO30 [2-h pre-IVM culture and 30-h IVM with dimethyl sulfoxide (DMSO)/vehicle control]. In vitro-matured oocytes were fertilized and presumptive zygotes were cultured in vitro to assess embryo development. In vivo blastocysts were produced from superovulated cows and used for gene expression analysis. Cleavage rates, blastocyst formation, and mRNA abundance of selected genes were evaluated. The Glimmix procedure from SAS/STAT (SAS Institute Inc., Cary, NC, USA) was performed to compare blastocyst and cleavage rates. One-way ANOVA was implemented to evaluate gene expression. A total of 793 oocytes from the different sources were submitted to the IVM treatments. Cleavage rates (prepubertal donors: 64.6 ± 4%, 59.1 ± 6.4%, 53 ± 4.4%, cows: 55.1 ± 4.3%, 59 ± 6.5%, 50.8 ± 4.4%, for TCM24, cAMP30, and DMSO30, respectively; P > 0.05) and blastocyst/zygotes rates (prepubertal donors: 27 ± 6%; 21.8 ± 3.5%; 17.6 ± 2.4%; cows: 28 ± 3.3%; 27.7 ± 2.9%; 22.7 ± 3.2% for TCM24, cAMP30, and DMSO30, respectively; P > 0.05) did not differ among in vitro treatments. The mRNA relative abundance of the EGR1 gene was down-regulated 6-fold in all in vitro-produced blastocysts compared with their in vivo counterparts (P < 0.05). Gene expression profiles for SLC2A8, DNMT3B, BCL-XL, and PRDX1 were similar in in vitro and in vivo blastocysts. These results show similar embryo production patterns in prepubertal and adult donors. Furthermore, DMSO did not show effects on embryo developmental rates when used during IVM. The gene expression levels of EGR1 confirm our recent findings in blastocysts obtained from oocytes from slaughterhouse ovaries (data not presented), showing its usefulness as an embryo quality marker. These preliminary results indicate that oocyte developmental capacity in prepubertal donors can be similar to that of the adult donors without addition of cAMP modulators.

scholarly journals Bovine oocyte developmental competence and gene expression following co-culturing with ampullary cells: An experimental study

2021 ◽  
Author(s):  
Mehdi Azari ◽  
Mojtaba Kafi ◽  
Anise Asaadi ◽  
Zohreh Pakniat ◽  
Beheshteh Abouhamzeh
Keyword(s):  
Gene Expression ◽  
In Vitro Maturation ◽  
Fertilization Rate ◽  
Developmental Competence ◽  
Control Group ◽  
Sufficient Information ◽  
Nuclear Maturation ◽  
Oocyte Developmental Competence ◽  
The Impact

Background: There is no sufficient information on the impact of bovine ampullary oviductal epithelial cells (BAOECs) on in vitro oocyte maturation competence and gene expression. Objective: This study aimed to examine the oocyte developmental competence following co-culturing with a monolayer of fresh and frozen-thawed ampullary cells. Materials and Methods: Bovine cumulus-oocyte complexes (COCs) were distributed into three groups: control group; where in COCs were cultured in cell-free media for 24 hr and FML and FTML groups in which the COCs were cultured in maturation media for 18 hr and then transferred into a media containing fresh and frozen-thawed BAOECs monolayer, respectively (BAOECs were extracted from the oviducts of slaughtered cattle and were then cultured freshly or frozen-thawed) for a further 6 hr. After 24 hr, the expanded COCs were evaluated for nuclear maturation, fertilization rate, and gene expression (GDF9, StAR, CASP3, and FSHr). Results: Nuclear maturation rate in the FTML group was significantly higher than the control group (p = 0.02). The fertilization rate of FTML group was significantly higher than the control and FML groups (p = 0.05 and p = 0.03, respectively). In terms of gene expression, GDF9 were upregulated in the presence of the BAOECs during the last 6 hr of the in vitro maturation (p < 0.001). Furthermore, the expression of the StAR gene in the FTML group was higher than the other groups (p = 0.02). Conclusion: Ampullary cells co-culturing (especially frozen-thawed cells) for in vitro maturation of bovine oocytes yields encourages the results and demonstrates the beneficial effect of co-culture on gene expression and developmental competence. Key words: Ampulla, Bovine, Fertilization, Gene expression, IVM.

Gene expression, oocyte nuclear maturation and developmental competence of bovine oocytes and embryos produced after in vivo and in vitro heat shock

Zygote ◽  
2016 ◽  
Vol 24 (5) ◽  
pp. 748-759 ◽  
Author(s):  
Krishna C. Pavani ◽  
Erica Baron ◽  
Pedro Correia ◽  
Joana Lourenço ◽  
Bruno Filipe Bettencourt ◽  
...  
Keyword(s):  
Gene Expression ◽  
Heat Shock ◽  
Embryo Development ◽  
Target Genes ◽  
Housekeeping Genes ◽  
Early Embryo ◽  
Developmental Competence ◽  
Nuclear Maturation

SummaryThree assays were performed. In assay 1, oocytes harvested during the winter months were subjected to kinetic heat shock by stressing the oocytes at 39.5°C (HS1) or at 40.5°C (HS2) for either 6, 12, 18 or 24 h and then matured at control temperature (38.5°C). The nuclear maturation rates (NMR) of all oocytes were recorded after 24 h. In assay 2, oocytes collected year-round maturated, were implanted via in vitro fertilization (IVF) and developed for 9 days. Gene expression analysis was performed on target genes (Cx43, CDH1, DNMT1, HSPA14) with reference to the two housekeeping genes (GAPDH and SDHA) in embryos. Similarly, in assay 3, genetic analysis was performed on the embryos produced from heat-stressed oocytes (from HS1 and HS2). In assay 1, the duration of heat stress resulted in a significant decline in NMR (P < 0.05) with HS1 for maturated oocytes at 86.4 ± 4.3; 65.5 ± 0.7; 51.3 ± 0.9; 38.1 ± 1.9 and 36.3 ± 0.9, for control, 6 h, 12 h, 18 h and 24 h, respectively. For assays 2 and 3, results demonstrated that DNMT1, Cx43 and HSPA14 were down-regulated in the embryos produced in the warm with respect to the cold months (P < 0.05). A constant up- and down-regulation of DNMT1 and HSPA14 genes were observed in both HS-treated samples. Also, an inconsistent pattern of gene expression was observed in Cx43 and CDH1 genes (P < 0.05). Targeted gene expression was aberrant in embryo development, which can provide evidence on early embryo arrest and slowed embryo development.

scholarly journals Cyclic nucleotide in oocyte In vitro maturation in Assisted Reproductive Technology

2020 ◽  
Vol 6 (3) ◽  
pp. 110-120
Author(s):  
Christie L Sun ◽  
Sally L Catt ◽  
Kiri Beilby ◽  
Mulyoto Pangestu
Keyword(s):  
Assisted Reproductive Technology ◽  
Natriuretic Peptide ◽  
In Vitro Maturation ◽  
Reproductive Technology ◽  
Developmental Competence ◽  
Nuclear Maturation ◽  
Oocyte Developmental Competence ◽  
Cytoplasmic Maturation ◽  
Camp Levels

In vitro maturation (IVM) is a promising assisted reproductive technology (ART) for human infertility treatment. However, when cumulus oocyte complexes (COCs) are removed from their follicular environment when manipulated in vitro, it can lead to a decrease of intra-oocyte cyclic adenosine 3’, 5’-monophosphare (cAMP) causing spontaneous nuclear maturation and an asynchrony with the oocytes’ cytoplasmic maturation, resulting in poor embryo developmental outcomes. Nuclear and cytoplasmic synchrony is important during oocyte maturation within antral follicles.It is maintained partially by the actions of c-type natriuretic peptide (CNP) binding with natriuretic peptide receptor 2 (NPR2), supporting high cAMP levels thus holding the oocyte in meiotic arrest. Addition of CNP to pre-IVM media has the capacity of maintaining cAMP levels and thus improve synchrony. Moreover, in women with advanced maternal age, successful IVM of aging oocytes faces significant challenges due to the morphological and cellular changes.  Inhibiting initiation of nuclear maturation by cAMP modulator, CNP during pre-IVM period and thus improve oocyte developmental competence regardless of oocyte age.

Effect of GnRH treatment on the maturation and in vitro development of oocytes collected from 4- to 6-week-old Merino lambs

2007 ◽  
Vol 19 (8) ◽  
pp. 947 ◽  
Author(s):  
Jennifer M. Kelly ◽  
David O. Kleemann ◽  
W. M. Chis Maxwell ◽  
Simon K. Walker
Keyword(s):  
In Vitro Maturation ◽  
Germinal Vesicle ◽  
Developmental Competence ◽  
Blastocyst Development ◽  
Cleavage Rate ◽  
Germinal Vesicle Breakdown ◽  
Nuclear Maturation ◽  
Oocyte Collection ◽  
Vitro Development

Two experiments were conducted in Merino lambs to examine the effects of gonadotrophin-releasing hormone (GnRH) treatment on the developmental competence of oocytes collected after pretreatment with follicle stimulating hormone (FSH). The first experiment examined the effects of six GnRH treatment times (control and GnRH administered 2, 4, 6, 8 and 10 h before oocyte collection) and four in vitro maturation (IVM) periods (18, 20, 22, 24 h) on the rate of oocyte nuclear maturation. The second experiment examined the effect of five GnRH treatment times (control and GnRH administered 2, 4, 6 and 8 h before oocyte collection) and three IVM periods (20, 22, 24 h) on the development of oocytes and embryos after in vitro maturation, fertilisation and culture. In Experiment 1, GnRH treatment did not influence the mean number of cumulus-oocyte-complexes (COCs) collected or COC morphology at the time of collection. However, treatment changed (P < 0.01) the distribution of follicle size and this was primarily due to a marked reduction in the number of follicles with diameters <2 mm. In addition, GnRH treatment at 6 and 8 h increased (P < 0.01) the proportion of oocytes that developed to Metaphase II (MII) (63.2 and 72.6%, respectively) compared with other treatment times (range 52.9–59.9%). Nuclear maturation was influenced by a significant (P < 0.05) interaction between GnRH treatment and IVM period due to a disproportionately greater number of oocytes at the germinal vesicle breakdown (GVBD) stage for the 2 and 4 h GnRH treatments compared with other treatments. In Experiment 2, cleavage rate (range 63.5–85.9%) was highest when GnRH was administered 8 h before collection but the percentage of cleaved oocytes that developed into blastocysts (range 10.0–35.0%) was significantly (P < 0.05) lower for the 6 and 8 h GnRH treatments compared with the control and the 2 h GnRH treatment. These results demonstrate that GnRH treatment before oocyte collection can improve nuclear maturation and cleavage rates in lamb oocytes but that these improvements are not reflected in improved rates of blastocyst development. It is speculated that this discrepancy may result from GnRH treatment either adversely affecting cytoplasmic maturation or inducing asynchrony between the maturation of the nuclear and cytoplasmic components of the oocyte.

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