Intrafollicular oocyte transfer (IFOT): Potential feasibility in the ovine species.

Intra-follicular oocyte transfer (IFOT) is a promising and innovative technique for in vivo embryo production previously described for equines and bovines. The aim of this study was to assess the feasibility of IFOT in the ovine species. Two preliminary in vivo and in vitro trials were performed to test the optimal procedures and timing for IFOT. In the in vivo trial, follicular growth was monitored with transrectal ultrasonography in ten adult ewes to preliminarily determine the ovulation and ideal timing for IFOT. The in vitro trial assessed i) the optimal inner diameter of the injection needle and ii) the recovery rate and integrity of injected cumulus-oocyte complexes (COCs) after follicle aspiration. For IFOT and embryo collection, five ewes were synchronized by CIDR insertion. Forty hours after CIDR removal, in ewes under sedation and general anesthesia, the ovaries were exposed by laparotomy, and the preovulatory follicle was injected with COCs previously collected from ovaries obtained from an abattoir. At 4 h after surgery, fully recovered ewes were housed in a paddock with a ram of proven fertility. Crayon marking on ram's chest was used to detect mating. Ovulation was assessed 40 h after the transfer of oocytes by transrectal ultrasonography. On day 6 after IFOT, embryo collection was performed by uterine flushing. In the in vitro testing, injection of >5 mm follicles with a 28 G needle loaded with 30 COCs in a 5 µL volume resulted in higher recovery rates and better preservation of COCs integrity. In the in vivo trial, ultrasound scanning revealed that ovulation occurred between 60 and 72 h after CIDR removal in all animals. In one ewe subjected to IFOT, 22/24 oocytes were effectively injected into the preovulatory follicle, but no embryos were collected after flushing. In the remaining four animals, 85/102 oocytes were injected, and six cleaved embryos, 12 morulae and 1 blastocyst were collected, including native embryos. This preliminary investigation indicated that IFOT in ovine species resulted in ovulation, fimbrial capture, tubal transport of heterologous oocytes and in vivo embryo production. Further studies are needed to optimize the embryo recovery rate and develop less invasive techniques for oocyte injection and uterine flushing, such as through a laparoscopic or transcervical approach.

The Design of a New Catheter for Transcervical Artificial Insemination in Ewes.

In ovine species, transcervical artificial insemination (TCAI) is limited by the poor quality of frozen-thawed semen and by the convoluted cervical lumen hampering the passage of inseminating devices. The aim of the study was to test the efficiency of three newly designed catheters with bent tips of 3.5 mm, 5.0 mm or 8.0 mm in terms of reproductive performances (experiment 1) and to compare the results of TCAI with the best performing catheter of experiment 1 to those obtained in ewes submitted to surgical incision of cervical folds (SICF) prior to insemination (experiment 2). The following parameters were assessed: time to pass the cervix; depth of cervical penetration; site of deposition of semen; pregnancy (PR); and lambing rates (LR). The results of experiment 1 indicated that the 5.0 mm tip catheter resulted in deeper and faster TCAI and higher PR and LR compared to 3.5 mm and 8.0 mm tip catheters (p < 0.05). In experiment 2, TCAI with the 5.0 mm catheter did not differ from TCAI after SICF in terms of depth of semen deposition, time to pass the cervix, PR and LR (p < 0.05). In conclusion, the use of a catheter that allowed transcervical uterine deposition of semen without excessive manipulation led to satisfactory pregnancy rates.

Resveratrol supplementation and cryopreservation of buck semen.

Resveratrol (Resv) was tested to assess its effects on buck semen freezability. Ejaculates of 4 bucks were collected, washed and diluted in a commercial extender at 30 °C. Extended semen was divided into 4 aliquots supplemented with increasing concentrations of Resv: 0 µM (control); 10 µM; 25 µM and 50 µM. Aliquots were cooled to 4 °C in 5h and frozen in LN2. Thawing was performed at 37 °C for 30 s. At the 3 stages of the experiment (30 °C, 4 °C, thawing), motility (CASA), osmotic resistance (Hos test) and integrity of cytoplasm and acrosome membranes (PI/PSA staining) were assessed. Moreover, in thawed samples, the oxidative status (MDA assay) and early apoptosis (DNA fragmentation by TUNEL assay) were evaluated. Resveratrol supplementation did not affect most of the motility parameters analysed, except for total motility, ALH (lateral head displacement) and velocity distribution (P < 0.05). Functional and morphological integrity of membranes was not affected at any stage of the experiment (P > 0.05). In thawed spermatozoa, the oxidative status was not preserved by Resv (P > 0.05) while early apoptosis, was significantly decreased in the 50 µM Resv group (P < 0.05). Resveratrol did not improve buck semen freezability; the observed effects on motility and DNA were not dose dependent and not mediated by a potential anti-oxidant activity.

Reproductive Performance Following Transcervical Insemination with Frozen Thawed Semen in Ewes Submitted to Surgical Incision of Cervical Folds (SICF): Comparison with Laparoscopic Artificial Insemination.

Transcervical artificial insemination (AI) after the surgical incision of cervical folds (SICF) could represent a valid alternative to laparoscopic AI when frozen thawed semen is used. The aim of this experiment was to compare pregnancy (PR) and lambing rates (LR) of ewes submitted either to transcervical AI after SICF or to laparoscopic AI using frozen thawed semen. Pregnant at term ewes (n = 80) were allocated in two experimental groups. After lambing, one group (n = 39) was submitted to SICF. The remaining ewes that were regularly lambed were allocated to the group of laparoscopic AI (n = 40). Six months later, oestrous cycle of both experimental groups was synchronised and all ewes were artificially inseminated with frozen thawed semen. Ewes submitted to SICF underwent transcervical insemination and intrauterine deposition of semen was recorded. The remaining animals were submitted to laparoscopic AI. Pregnancy and LR were recorded. Intrauterine deposition of semen was possible in 89.7% pf ewes submitted to SICF. This group showed similar PR and LR compared to the laparoscopic group (respectively: PR, 71.8% vs. 70% and LR, 64.1% vs. 65%; p > 0.05). Transcervical AI after SICF may represent a valid alternative to laparoscopy in AI protocols requiring the use of frozen thawed semen.

Resveratrol treatment during maturation enhances developmental competence of oocytes after prolonged ovary storage at 4 °C in the domestic cat model.

Resveratrol (Resv; 3,4,5-trihydroxy-trans-stilbene) is a phytoalexin with antioxidant activity that modulates redox homeostasis in oocytes and improves in vitro embryo production. Cold storage of cat ovaries for a period longer than 24 h alters oxidative status of oocytes after in vitro maturation and reduces their developmental competence. The aim of this study was to evaluate the effect of resveratrol supplementation to the maturation medium on embryo development of oocytes after storage of domestic cat ovaries at 4 °C for 24 h or 48 h. Cumulus-oocyte complexes (COCs) were recovered from ovaries of domestic queens and cultured in maturation medium supplemented with (+) or without (-) 5 µM resveratrol for 24 h. COCs collected from fresh ovaries were matured in vitro (IVM) in standard conditions as control. After IVM, oocytes were in vitro fertilized (IVF) and presumptive zygotes cultured for 7 days. Oocyte nuclear maturation, reactive oxygen species (ROS) and glutathione (GSH) levels as well as cleavage, blastocyst formation and blastocyst cell number were determined. There were no differences in the maturation rates of oocytes between the control and stored groups, irrespective of resveratrol supplementation. Resveratrol treatment during IVM significantly increased the level of GSH and reduced the level of ROS of oocytes recovered from ovaries stored for 48 h as compared to the non-treated group (48 h-). The rate of blastocyst formation from oocytes recovered from ovaries after 48 h storage that underwent IVM with resveratrol was higher (P < 0.05) than that of oocytes matured without resveratrol and similar to that of control oocytes. Resveratrol treatment increased (P < 0.05) cell number in blastocysts from 24 h + and 48 h + groups as compared to their respective counterparts. In conclusion, our results demonstrated that resveratrol supplementation during IVM can reverse the adverse effect of oxidative stress on oocytes, and enhances embryo development after ovary storage at 4 °C for 48 h. These results may provide a basis for improving culture conditions and extend the possibility of storage of cat ovaries for more than 24 h thus ensuring successful in vitro embryo production.

Surgery on cervical folds for transcervical intrauterine artificial insemination with frozen-thawed semen enhances pregnancy rates in the sheep.

In sheep industry, genetic progress rate achieved by artificial insemination (AI) is limited by the convoluted anatomy of the cervix, which does not allow the passage of an insemination catheter for uterine semen deposition. The aim of this study was to test, in 98 pregnant at term Sarda ewes, the effects of: Experiment 1) total or partial ablation of cervical folds and Experiment 2) 4 or 2 incisions of cervical folds, on the passage of an insemination catheter, deposition of frozen-thawed semen and pregnancy rates. Surgical procedures were performed within 24 h from parturition providing deep sedation and epidural anaesthesia. Duration of surgeries and post-operatory recovery were carefully monitored. For both experiments, 5 months since surgery, independently of the stage of oestrus cycle, cervical patency was tested through the transcervical passage of a palpation probe. Six months since surgery, in Experiment 1, ewes were naturally mated with fertile rams. In Experiment 2, ewes submitted to incisions of the cervical folds and a control group underwent synchronisation of oestrus and transcervical AI with frozen-thawed semen. Thirty days later, for both experiments, pregnancy rates were assessed by ultrasonography and lambing rates were recorded. Five months after surgery, in Experiment 1, transcervical passage of a palpation probe to reach the uterine lumen was possible in all ewes submitted to total and partial ablation of folds. In Experiment 2, this was achievable in 90.5% ewes with 4 incisions of the folds and in 89.6% ewes with 2 incisions with no significant differences among groups (P = 0.44). In Experiment 1, pregnancy rates in ewes mated to rams after total or partial ablation of the cervical folds was 100%. In Experiment 2, following transcervical AI, pregnancy rates were higher in groups submitted to 4 (63.7%) or 2 (41.4%) incisions of the cervical folds compared to the control group (8%; P<0.05). These data were confirmed at lambing with rates of 56.8% and 41.4% in ewes submitted to 4 or 2 incisions respectively, significantly higher than the control group (4%; P<0.05). Surgical ablation or incision of the cervical folds in post-partum ewes represent valid procedures for transcervical intrauterine deposition of semen for AI, obtaining satisfactory pregnancy rates. These procedures might be useful in programs of genetic selection and MOET.

Structure of preantral follicles, oxidative status and developmental competence of in vitro matured oocytes after ovary storage at 4 °C in the domestic cat model.

BACKGROUND: Storage conditions during transportation of explanted ovaries are a critical step in setting up fertility preservation protocols in both animal and human fields. Here, we evaluated the effects of ovary storage at 4 °C on the preservation of preantral follicles and oocytes retrieved from antral follicles using the domestic cat as model. METHODS: Ovaries were harvested from fifty-five healthy domestic queens during ovariectomy and stored at 4 °C for 0 (control), 24, 48, 72 and 96 h. In Experiment 1, the effects of the storage period at 4 °C on the morphology, cytoskeleton (α/ß tubulin) and DNA integrity (phosphorylation of histone H2AX) of preantral follicles were investigated. In Experiment 2, oocytes recovered from antral follicles were matured and fertilized in vitro to evaluate their meiotic and developmental competence. Reactive oxygen species (ROS), glutathione (GSH) and lipid peroxidation were measured in matured oocytes. RESULTS: The results showed that: a) storage up to 24 h did not affect the morphology and the DNA integrity of preantral follicles; b) extended storage times caused progressive morphological abnormalities, disassembling of microtubules and DNA damage; c) storage up to 48 h did not influence in vitro meiotic maturation of oocytes nor cleavage after in vitro fertilization. However, only oocytes stored within the ovary for 24 h produced blastocysts in a percentage similar to control oocytes; d) GSH levels of in vitro matured oocytes did not change at any time during ovary storage; a progressive increase in ROS levels was detected from 48 h associated with elevated lipid peroxidation at 72 and 96 h of storage. CONCLUSIONS: Storage of cat ovaries for up to 24 h caused minimal alteration of preantral follicles and oocytes. The extension of the storage period beyond 24 h progressively impaired the structure of follicles, and modified the oxidative status of in vitro matured oocytes and their developmental competence after in vitro fertilization. This information may help when setting up programs for fertility conservation, especially for wild feline species which die in geographic areas located far away from ARTs centers.

Effect of exposure to CeO2 nanoparticles on ram spermatozoa during storage at 4 °C for 96 hours.

BACKGROUND: Cerium oxide nanoparticles (CeO2 NPs) are able to store and release oxygen, conferring them scavenger activity against oxidative stress. However, their effects in reproductive systems are not yet well understood. The aim of the study was to investigate the effects of exposure of refrigerated ram semen to CeO2 NPs for 96 h on the main structural and kinematic parameters of spermatozoa. METHODS: The ejaculates of 5 Sarda rams were collected, pooled and diluted in a soybean lecithin extender. Samples were exposed to increasing doses of CeO2 NPs (0, 44 and 220 µg/mL) and stored at 4 °C for 96 h. Analyses of kinematic parameters (computer assisted sperm analysis, CASA), integrity of membranes (PI/PSA staining), ROS production (H2DCFDA staining) and DNA damage (sperm chromatin structure assay with acridine orange, SCSA) were performed every 24 h (0, 24, 48, 72 and 96 h of incubation). The experiment was carried out in 6 replicates. Data were analysed by repeated measures ANOVA with Bonferroni's as post hoc test. When the assumption of normality was not met (ROS), non-parametric Kruskal-Wallis rank test was carried out. RESULTS: Exposure of ram spermatozoa to increasing doses of CeO2 NPs had a beneficial effect on the main motility parameters from 48 h of incubation onward. Velocity of sperm cells was enhanced in the groups exposed to CeO2 NPs compared to the control. Incubation with NPs had beneficial effects on the integrity of plasma membranes of spermatozoa, with higher percentage of damaged cells in the control group compared to the exposed ones. Production of ROS was not affected by exposure to NPs and its levels rose at 96 h of incubation. The integrity of DNA remained stable throughout the 96 h of storage regardless of co-incubation with NPs. CONCLUSIONS: We reported beneficial effects of CeO2 NPs on kinematic and morphologic parameters of ram semen, such as motility and membrane integrity following 96 h of exposure. Furthermore, we also proved no genotoxic effects of CeO2 NPs. These effects could not be related to an antioxidant activity of CeO2 NPs, since ROS levels in exposed cells were similar to those of unexposed ones.

Hypoluteoidism in a dog associated with recurrent mammary fibroadenoma stimulated by progestin therapy.

BACKGROUND: Hypoluteoidism in the bitch is characterized by insufficient production and secretion of progesterone by the corpora lutea. It is a rare pathologic condition and during pregnancy, it leads to embryonic resorption or fetal abortion. Supplementary therapy with progestins is indicated during pregnancy to obtain delivery of vital puppies but unwarranted side effects of such treatment are poorly documented. CASE PRESENTATION: A 4-year-old, nulliparous, female Istrian Shorthaired Hound dog had been mated repeatedly in six heats with different dogs of proven fertility but signs of pregnancy did not develop. Estrous cycles, mating and pregnancies were monitored as hypoluteoidism or genital disease was suspected. During the first monitored estrus, the bitch was mated and on day 18 [day 0, day of estimated peak of luteinizing hormone (LH)], ultrasound examination showed three amniotic vesicles that were however found to be resorbed between day 20 and 23. Progesterone concentrations, measured by ELISA, were >8 ng/mL until day 12 and 1-2.5 ng/mL on days 20, 23 and 26. Primary hypoluteoidism was therefore suspected. In the second monitored estrus, the bitch was mated and during pregnancy, progesterone concentrations were >8 ng/mL until day 17 and 1-2.5 ng/mL on day 19. On days 20 and 22, two out of three embryonic vesicles had been resorbed. The bitch was treated with progesterone in oil from day 19 to day 58. Increase in the size of 2nd left thoracic mammary gland (T2-L) was observed and on day 46, ultrasound evaluation and biopsy were performed revealing a low-cellularity fibroadenoma. Parturition started spontaneously at day 65 but due to dystocia caused by fetal macrosomia, a Caesarean section was performed. During the next (third) monitored estrus, the bitch was bred again and during pregnancy, early decrease in progesterone concentration confirmed the diagnosis of primary hypoluteoidism. The bitch was treated with synthetic progestin (altrenogest) from day 8 to day 57. Five amniotic vesicles were detected by ultrasonography. Recurrence of swelling of T2-L was observed. On day 60, the bitch whelped five pups, two males and three females. As reported later by the owner, the latter did not show any sign of heat over the past 3 years. In one of them, clitoral hypertrophy and a blind ending vagina were diagnosed. CONCLUSIONS: This is the first description of early hypoluteoidism in a pregnant bitch developing a mammary fibroadenoma under progestin treatment.

Host cell tropism, genome characterization, and evolutionary features of OaPV4, a novel Deltapapillomavirus identified in sheep fibropapilloma.

Investigating papillomavirus (PV) diversity is crucial to fully comprehend pathogenicity, genetic features, and evolution of taxa hosted by domestic and wild animal species. This study reports the identification of OaPV4, a novel ovine PV type within Deltapapillomaviruses 3. The study of OaPV4 genomic features combined to in situ hybridization and immunohistochemistry investigations allowed extrapolating several general biological features of ovine PVs, such as their cellular tropism, pathogenicity, and evolutionary history. Based on results, ovine PVs can be grouped into a polyphyletic ancient group of viruses, which splits in two main subgroups having peculiar cellular tropism and pathogenicity. Results add up to animal PV diversity and are crucial to future studies aimed to investigate the correlation between animal PV and cutaneous benign and malign proliferations.

Immature ovarian teratoma in two heifers.

A 15 months-old Simmental heifer (SH) and a 18 months-old Marchigiana heifer (MH) were referred to the Faculty of Veterinary Medicine of Teramo (Italy). In the rst heifer, clinical examination of the vulva, vestibulum, and vagina showed no signs of disease and no discharge was detected. Palpation per rectum revealed a mass in the left portion of the abdominal cavity, closely attached to the tip of the left uterine horn. The mass was mainly rm and brous and its surface was slightly lobulated. The second heifer had a history of a regular cycle from the 11th to the 14th month of age followed by an anoestrus state. Gynecological examination revealed the presence of a large and rm mass in the caudal left region of the abdomen, soon over the edge of the pelvis oor. In both cases, the histologica examination of the mass revealed an immature ovarian teratoma.

Vaginal fold prolapse in a dog with pyometra and ovarian papillary cystadenocarcinoma.

CASE DESCRIPTION: A 7-year-old 42-kg (92.4-lb) sexually intact nulliparous female Italian Mastiff was examined because of a history of vaginal prolapse during diestrus. CLINICAL FINDINGS: A physical examination revealed vaginal fold prolapse. Abdominal ultrasonography revealed an enlarged uterus with hypoechogenic content, corpora lutea in the ovaries, and a cyst in the right ovary. Hematologic abnormalities included leukocytosis, neutrophilia, mild anemia, and low Hct. Progesterone and estradiol concentrations were 9.36 ng/mL and 30.42 pg/mL, respectively, in serum and 72.72 ng/mL and 792 pg/mL, respectively, in the ovarian cystic fluid. TREATMENT AND OUTCOME: Ovariohysterectomy was performed; the prolapsed tissue was repositioned by external manipulation and maintained in situ by temporary apposition of the vulvar lips with a retention suture. Anatomic and histologic examinations of the excised tissues revealed pyometra and papillary cystadenocarcinoma in the right ovary. The vaginal hyperplasia completely regressed at 35 days after surgery; 5 months after surgery, the dog's general condition was considered good. CLINICAL RELEVANCE: Findings in this case were indicative of a hormonally active ovarian papillary cystadenocarcinoma in a female dog in diestrus. Hormone production by the cystadenocarcinoma was the predisposing factor that induced pyometra, mucosal hyperplasia, and vaginal fold prolapse in the dog. On the basis of these concurrent disorders, ovariohysterectomy was an appropriate treatment.

Lipid droplet distribution of immature canine oocytes in relation to their size and the reproductive stage.

This study investigated the distribution of lipid droplets (LD) in immature canine oocytes in relation to their size and the reproductive stage. Oocytes were collected from the ovaries of bitches at different estrous stages, divided according to their size (110-120 µm; >120 µm), and stained with Nile Red to detect lipid droplet distribution. At the follicular phase most of the oocytes displayed a diffuse pattern of LD distribution, whereas at anestrus and luteal phase oocytes showed LD mainly in a peripheral/ perinuclear LD distribution. A significantly higher intensity of LD has been recorded in the oocytes > 120 µm compared to those of smaller size (110 - 120 µm) at all stages of the estrous cycle. At follicular phase, oocytes > 120 µm displayed LD intensity similar to that of oocytes > 120 µm at luteal phase and higher compared to the oocytes of the other groups.

Unveiling mRNA changes during meiotic progression and pre-implantation development: help from large animal models.

Assisted reproductive technologies (ART) are successfully applied in several mammals, including humans, thanks to the ability of oocytes and embryos to face maturation, fertilization and first development in vitro. However, efficiency and safety of ART represent main issues. Mammalian oocytes and early embryos are transcriptionally inactive, and rely exclusively on maternal RNAs and proteins, deposited during oocyte growth, until embryonic genome activation (EGA). Such transcriptional quiescence needs complex post-transcriptional and post-translational mechanisms to coordinate meiotic maturation, fertilization, and reprogramming of the nascent genome. These events are the final outcome of complex, hormonally regulated biological processes that translate into specific molecular mechanisms, which are still far from being fully understood. A deep knowledge of these early phases of development is crucial to understand the core mechanisms of life onset, and to optimize the safety and efficiency of in vitro reproductive technologies. This work focuses on meiotic progression and pre-implantation development in mammals, underlining the importance of fundamental molecules stored during oocyte growth and selectively used during early embryogenic stages. Taking into account the species-specific behaviour of these pivotal molecules, this review describes the advantages of using large domestic animals for research in the reproductive field and proposes large domestic animals as models to improve human ART.

The effect of okadaic acid on meiotic maturation of canine oocytes of different size.

The present study was conducted to determine the effect of okadic acid (OA), a potent inhibitor of seronine/treonine 1 and 2A phosphatase, on meiotic resumption and progression in canine oocytes with different diameters. Cumulus-oocyte complexes were collected from ovaries of bitches at different oestrous phases. In Experiment 1, to determine the optimal concentration of OA (0.5 or 2 µM), the oocytes were pre-incubated for 1, 3, and 20 h in TCM 199 supplemented with 20% SCE and thereafter cultured in the same medium without OA. In Experiment 2, the selected oocytes were divided into three groups according to their diameter: <110 µm, 110-120 µm, >120 µm, and pre-incubated in OA 0.5 µM for 1 h. Oocytes were cultured in vitro as previously described. After 72 h of IVM, in Experiment 1, significantly more oocytes reached MII stage with 0.5 µM for 1 h (30.8% P<0.001%) for oocytes cultured in other OA condition and in control group. In Experiment 2, OA induced a significantly higher incidence of MII oocytes in the 110-120 µm and >120 µm groups (P<0.001) compared to control group, but a significantly higher proportion of the oocytes>120 µm pre-incubated with OA progressed to MII (51.3% P<0.001). In contrast, smaller oocytes (<110) did not develop to MII stage with or without OA. In conclusion, treatment of canine oocytes with 0.5 µM for 1 h, improves meiotic maturation. The culture of fully grown (>120 µm) oocytes with OA at the onset of in vitro maturation can result in a higher frequency of meiotic maturation.

Influence of co-culture with oviductal epithelial cells on in vitro maturation of canine oocytes.

The process of oocyte maturation in the canine species is unique among mammals: oocytes are immature at ovulation and the resumption and progression of meiotic maturation occur in the oviduct. This study was performed to investigate (i) the effect of co-culture with infundibulum and ampullar oviductal epithelial cells on the in vitro maturation of canine oocytes and (ii) the culture time necessary to reach full meiotic maturation. For this purpose the oocytes, collected from the ovaries of bitches undergoing ovariectomies, were divided into three groups and cultured for 48 and 72 h with the following systems: (A) TCM 199 + 10% oestrus bitch serum + FSH (0.1 IU.mL(-1)), LH (0.1 IU.mL(-1)) + progesterone (1 microg.mL(-1)) + oestradiol (1 microg.mL(-1)) + cysteamine (100 microM); (B) medium A plus infundibulum cells; (C) medium A plus ampullar cells. Infundibulum and ampullar cells were recovered from the oviducts of bitches at the oestrus stage of their cycle. The results showed that after 48 h of incubation, a significantly higher meiotic resumption (P < 0.01) was observed in the oocytes cultured with infundibulum (59%) and ampullar cells (60.0%), than in the control group (40.0%). There was also a significantly (P < 0.01) higher meiotic progression to the MII in systems B and C (15.6% and 16.7%) than in system A (4.0%). After 72 h of culture, the percentages of meiotic resumption and progression were unchanged. These results showed that both the infundibulum and the ampullar oviductal epithelial cells positively influence the meiotic resumption and progression of canine oocytes and that 48 h are sufficient for the completion of nuclear maturation.