scholarly journals Seasonal Effect on Developmental Competence, Oxidative Status and Tubulin Assessment of Prepubertal Ovine Oocyte

Animals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1886
Author(s):  
Elisa Serra ◽  
Sergio Domenico Gadau ◽  
Giovanni Giuseppe Leoni ◽  
Salvatore Naitana ◽  
Sara Succu
Keyword(s):  
In Vitro Maturation ◽  
Reproductive Activity ◽  
Oocyte Quality ◽  
Developmental Competence ◽  
Seasonal Effect ◽  
Mitochondrial Activity ◽  
Reproductive Seasonality ◽  
Embryo Production

The reproductive seasonality of domestic animals is often manipulated in order to have more reproductive periods for commercial purposes related to the production of milk and meat. It is scientifically proven that such an alteration of the reproductive activity in sheep entails a deterioration in oocyte quality, leading to an inability to generate embryos. Since oocytes obtained from prepubertal ewes can be incorporated into an in vitro embryo production system and considering that their quality is crucial to the success of in vitro procedures, the aim of this work was to investigate the effect of seasons on the quality of prepubertal ovine oocytes collected in autumn and spring. Ovaries were collected from a local slaughterhouse from 30–40-day-old suckling lambs during both seasons. Following 24 h of in vitro maturation, oocytes developmental competence, reactive oxygen species (ROS) intracellular levels, and mitochondrial activity were evaluated, and a tubulin assessment was performed. The results on embryo production, as a percentage of first divisions and number of blastocysts obtained, were significantly higher in oocytes collected in the spring. Mitochondrial activity in oocytes was higher, and ROS production significantly lower, in spring than in autumn. Tubulin PTMs (tyrosinated and acetylated α-tubulin) showed a higher immunoreactivity in oocytes collected in spring compared with autumn sampling. Our data showed that seasons may affect the developmental competence, energetic status, and tubulin assessment of oocytes recovered from prepubertal ewes. Therefore, special care should be taken when choosing the period of the year for prepuberal ovine oocytes collection aimed at in vitro embryo reproduction programs.

253 OXIDATIVE STRESS MAY IMPAIR OOCYTE QUALITY IN DAIRY COWS OF REPRODUCTIVE AGE WITH A REDUCED ANTRAL FOLLICLE COUNT

2013 ◽  
Vol 25 (1) ◽  
pp. 274 ◽  
Author(s):  
I. Tessaro ◽  
F. Franciosi ◽  
V. Lodde ◽  
D. Corbani ◽  
A. M. Luciano ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Nitric Oxide ◽  
Antral Follicle ◽  
Oocyte Quality ◽  
Antral Follicle Count ◽  
Oxide System ◽  
Reproductive Age ◽  
Developmental Competence ◽  
Mitochondrial Activity

In dairy cattle, oocytes isolated from ovaries with a reduced antral follicle count (AFC) have a low embryonic developmental competence. This may be related to oxidative stress, as indicated by our recent finding that ovaries with reduced AFC show a defective endothelial nitric oxide synthase/nitric oxide system. To further test this hypothesis, we evaluated whether the poor developmental competence of these oocytes was possibly due 1) to an imbalance of the reduced glutathione (GSH) system, because GSH is the major antioxidant compound stored within the oocyte and protects the zygote and early embryos from oxidative damage, and 2) to reduced mitochondrial activity. Ovaries were obtained from the abattoir, and oocytes were collected from ovaries with reduced AFC, with fewer than 10 follicles of 2 to 6 mm in diameter, and aged-matched controls, with more than 10 follicles of 2 to 6 mm in diameter. Oocyte GSH content was evaluated using the 5,5′-dithio-bis(2-nitrobenzoic acid)-GSH reductase recycling micro-GSH assay before and after in vitro maturation (IVM) in the presence or absence of 100 µM cysteamine, a GSH precursor. At the same time the developmental competence after IVF was assessed. Moreover, the mitochondrial activity during IVM was evaluated in additional oocytes from the two ovarian categories by specific MitoTracker dyes (MitoTracker FM Green and MitoTracker Orange CMTMRos, Invitrogen, Carlsbad, CA, USA) and subsequent image analysis (ImageJ software). All data were analysed by ANOVA followed by Fisher’s least significant differences test, and P-values <0.05 were considered significant. Experiments were repeated at least three times. Oocytes isolated from ovaries with a low AFC had a similar GSH content compared with oocytes isolated from control ovaries (n = 65 and 85, respectively; 4.31 ± 0.41 v. 4.51 ± 0.42 pmol oocyte–1). After IVM, oocytes from ovaries with reduced AFC showed a significantly lower GSH content compared with control oocytes (n = 55 and 65, respectively; 4.36 ± 0.31 v. 6.59 ± 0.39 pmol oocyte–1); however, cysteamine supplementation during IVM induced GSH accumulation similar to the control (n = 80 and 85, respectively; 9.88 ± 0.77 v. 10.45 ± 0.88 pmol oocyte–1). It is interesting that the increase in intracellular GSH content significantly improved the developmental competence of oocytes from ovaries with a reduced AFC (n = 196 and 201, respectively; 20.1 ± 2.9% v. 6.2 ± 1.6%), although the blastocyst rate remained lower than the control either with or without cysteamine (n = 218 and 212, respectively; 33.3 ± 3.8% and 34.2 ± 2.4%). Further, immature oocytes from ovaries with a low AFC showed a reduced mitochondrial membrane potential compared with control oocytes (n = 13 and 18, respectively; 1.74 ± 1.19 v. 2.22 ± 1.72, calculated as the ratio between the fluorescence of active and total mitochondria), whereas at the end of IVM, it declined in both categories at a comparable level (n = 17 and 24, respectively; 1.19 ± 0.10 and 1.30 ± 0.06). Our data confirmed the hypothesis that both the GSH imbalance and defective mitochondrial activity contribute to the limited developmental competence of oocytes from ovaries with a reduced AFC. This work was supported by Dote ricerca applicata-FSE, Regione Lombardia, Italy (VL, IT).

205 CUMULUS CELL MORPHOLOGY BEFORE AND AFTER IN VITRO MATURATION AS AN INDICATOR OF PORCINE OOCYTE DEVELOPMENTAL COMPETENCE

2010 ◽  
Vol 22 (1) ◽  
pp. 260
Author(s):  
M. Bertoldo ◽  
P. K. Holyoake ◽  
G. Evans ◽  
C. G. Grupen
Keyword(s):  
Cell Morphology ◽  
In Vitro Maturation ◽  
Cumulus Cell ◽  
Cumulus Cells ◽  
Oocyte Quality ◽  
Developmental Competence ◽  
Oocyte Developmental Competence ◽  
Before And After ◽  
Follicle Size

Effective in vitro maturation (IVM) is essential for successful in vitro embryo production. The morphology of the cumulus investment before and after IVM may be a useful noninvasive indicator of oocyte quality. In pigs, oocyte developmental competence is reduced during the summer months. The aim of this study was to determine whether the morphology of cumulus-oocyte complexes (COC) before and after IVM are associated with oocyte quality, using COC collected from small and large follicles in summer and winter as models of poor and good oocyte quality. Ovaries were collected from sows slaughtered 4 days after weaning. The COC recovered from small (3-4 mm) and large (5-8 mm) antral follicles were morphologically graded and parthenogenetically activated following IVM during winter (n = 1419; 10 replicates) and summer (n = 2803; 10 replicates). Grade 1 and 2 COC had >2 layers of compact cumulus cells and a homogenous cytoplasm. Grade 3 COC were either partially or fully denuded, had a heterogeneous cytoplasm, or were vacuolated or dark in color. Grade 4 COC had expanded cumulus cells. Cumulus expansion was also assessed subsequent to IVM. The COC recorded as having a cumulus expansion index (CEI) of 1 had the poorest expansion with no detectable response to IVM, whereas those with a CEI of 4 had the greatest amount of expansion, including that of the corona radiata. Data were analyzed using a generalized linear mixed model in GenStat® (release 10, VSN International, Hemel Hempstead, UK). There was an effect of follicle size for Grade 1 COC, with COC from large follicles in both seasons yielding better quality COC (P < 0.05). The proportion of COC in Grade 2 was higher in small follicles during winter compared with large follicles, but there were no differences between follicle sizes during summer (P < 0.05). The proportion of COC with CEI 1 was highest in COC from small follicles during summer (P < 0.05). The proportion of COC from large follicles with CEI 2 was higher during summer compared with winter (P < 0.05). There were no seasonal or follicle size effects on COC with CEI 3 or 4 (P > 0.05). The proportion of oocytes that developed to blastocysts was greater in winter than in summer (39.06% ± 5.67 v. 22.27% ± 4.01; P < 0.05). Oocytes derived from large follicles had a greater ability to form blastocysts compared with those from small follicles (37.13% ± 5.65 v. 23.32% ± 4.56; P < 0.06). Morphological assessment of cumulus cells before and after IVM may be a useful tool to evaluate the effects of follicle size on oocyte developmental competence. However, the results of the present study indicate that cumulus cell morphology is not a good indicator of the effect of season on oocyte developmental competence.

75 Improvement of Developmental Competence of Bovine In Vitro-Produced Embryos by Using Charcoal:Dextran-Stripped Fetal Bovine Serum on In Vitro Culture Media

2018 ◽  
Vol 30 (1) ◽  
pp. 176
Author(s):  
A. Mesalam ◽  
R. Kong ◽  
B.-H. Choi ◽  
K.-L. Lee ◽  
B.-Y. Park ◽  
...  
Keyword(s):  
In Vitro Culture ◽  
Bovine Serum ◽  
Culture Media ◽  
Fetal Bovine Serum ◽  
Developmental Competence ◽  
Mitochondrial Activity ◽  
Mrna Levels ◽  
Fetal Bovine

Serum has widely been used as a main supplement to embryo in vitro culture media as it contains embryotrophic factors. Charcoal:dextran treatment of fetal bovine serum (FBS) removes lipophilic chemicals and certain steroid hormones and growth factors. The objective of this study was to investigate the effects of charcoal:dextran-stripped fetal bovine serum (CDS FBS) and heat-inactivated FBS (HI FBS) in embryo culture medium (SOF-BE1 medium supplemented with 10% of serum) on their ability to support in vitro development of bovine embryos. The developmental ability and quality of bovine embryos were determined by assessing their cell number, lipid content, mitochondrial activity, gene expression, and cryo-tolerance. The experiment was conducted in 6 replicates (350 oocytes per group). The differences in embryo development, integrated optical intensity, and expression levels of the various genes between experimental groups were analysed by one-way ANOVA. Duncan’s multiple range tests were used to test the differences between the treatments. The level of statistical significance was set at P < 0.05. The percentages of embryos that underwent cleavage and formed a blastocyst were significantly (P < 0.05) higher in medium containing CDS FBS than in medium containing HI FBS (42.84 ± 0.78% v. 36.85 ± 0.89%, respectively). The total number of cells per Day 8 blastocyst was not significantly different (P > 0.05) between the CDS FBS group (208.40 ± 14.77) and the HI FBS group (195.11 ± 19.15). Furthermore, the beneficial effects of CDS FBS on embryos were associated with a significantly increased mitochondrial activity, as identified by MitoTracker Green, and reduced intracellular lipid content, as identified by Nile red staining, which increased their cryo-tolerance. The post-thaw survival rate of blastocysts was significantly (P < 0.05) higher after 24 h in the CDS FBS than in the HI FBS group (85.33 ± 4.84% v. 68.67 ± 1.20%). Quantitative reverse transcription PCR showed that the mRNA levels of lipid metabolism-related genes, acyl-CoA synthetase long-chain family member 3, acyl-coenzyme A dehydrogenase long-chain, and the cholesterol metabolism related gene hydroxymethylglutaryl-CoA reductase were significantly increased upon culture with CDS FBS. Moreover, the mRNA levels of survival gene sirtuin 1, antioxidant gene superoxide dismutase 2, and anti-apoptotic associated gene B-cell lymphoma 2 in frozen–thawed blastocysts were significantly (P < 0.05) higher in the CDS FBS group than in the HI FBS group; however, the mRNA level of the pro-apoptotic gene BCL2-associated X protein was significantly reduced. In conclusion, these data suggest that supplementation of in vitro culture medium with CDS FBS improves in vitro bovine embryo developmental competence and the quality of blastocysts in terms of their crytolerance and gene expression. This research was supported by grant from the Next-Generation BiogGeen21 (No. PJ01107703), IPET (No. 315017-5 and 117029-3), Allergy free cat (Co.. Felix Pets), BK21plus, and KGSP.

scholarly journals Lipid content, mitochondrial activity and early embryo development in oocyte collected from crossbred cows (bos taurus indicus)

2018 ◽  
Vol 25 (1) ◽  
pp. 120-131
Author(s):  
Yoeli Mendez ◽  
Nohely Parra ◽  
Francisco Baez ◽  
Robert Valeris ◽  
Patricia Villamediana
Keyword(s):  
Lipid Content ◽  
Lipid Droplets ◽  
Oocyte Quality ◽  
Early Embryo ◽  
Developmental Competence ◽  
Mitochondrial Activity ◽  
Vitro Fertilization ◽  
Immature Oocytes ◽  
Crossbred Cows

The objective of this research was to evaluate the effect of phenotypic predominance on lipid content, mitochondrial activity and early developmental competence as indicators of oocyte quality. Cumulus-oocyte complexes (COCs) were recovered through follicular aspiration, and underwent in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro culture (IVC) of presumptive zygotes. Lipid content and mitochondrial activity in immature and IVM oocytes were determined. A maturation rate of 80.6% and 69.3% was found for oocytes predominantly B. indicus and predominantly B. taurus, respectively. Total fertilization rate was 27.6%; 26.1% for predominantly B. indicus oocytes and 29% for predominantly B. taurus oocytes. A total of 55.5% and 57.5% of cleaved embryos after 48 and 72 h post-insemination (hpi) in predominantly B. indicus group were observed, respectively. As for the predominantly B. taurus group, 48.6% and 60.4% of cleaved embryos were found after 48 and 72 hpi, respectively. In both groups, immature oocytes showed a greater amount of small lipidic droplets (p <0.0001); IVM decreased the number of small lipid droplets (p < 0.0001) and increased the number of medium and large lipid droplets (p < 0.0001). Predominantly B. indicus oocytes had a greater number of small and medium-sized lipid droplets, while there were no significant differences in large lipid droplets. IVM oocytes had higher mitochondrial activity than immature oocytes group (p < 0.05) without any effect of phenotypic predominance on this parameter. Assessment of lipid content was not a predictive factor of oocyte quality in crossbred cows.

170 INFLUENCE OF OOCYTE QUALITY AND DIFFERENT MEDIA SUPPLEMENT ON IN VITRO MATURATION, CLEAVAGE, AND EMBRYO DEVELOPMENT OF BUFFALO (BUBALUS BUBALIS) OOCYTES

2014 ◽  
Vol 26 (1) ◽  
pp. 199
Author(s):  
M. M. Waheed ◽  
K. H. El-Shahat ◽  
A. M. Hammam
Keyword(s):  
Embryo Development ◽  
In Vitro Maturation ◽  
Cumulus Cell ◽  
Oocyte Quality ◽  
Bubalus Bubalis ◽  
Poor Quality ◽  
Developmental Competence ◽  
Control Group ◽  
Excellent Quality

A series of 4 factorial-arranged experiments were conducted to study the effect of oocyte quality and different in vitro maturation (IVM) media supplements on IVM, cleavage, and embryo development of buffalo (Bubalus bubalis) oocytes. Buffalo ovaries were collected at a local abattoir in a warm (32–35°C) saline (0.9% NaCl), and oocytes were aspirated using an 18-gauge needle. In experiment 1, oocytes (n = 320) were classified according to the number of cumulus cell layers and morphology of ooplasm as excellent, good, or fair. Oocytes were cultured for IVM, fertilization, and embryo culture (IVMFC) in TCM-199 + 10% FCS. In experiment 2, excellent quality oocytes (n = 237) were subjected to IVM in TCM-199 enriched with either 10% FCS or oestrous buffalo serum (EBS; 20–40 pg mL–1) and then fertilized using frozen–thawed buffalo semen capacitated in Bracket and Oliphant's (BO) medium containing heparin (0.02 mg mL–1) and sodium caffeine benzoate (3.89 mg mL–1). In experiment 3, oocytes (n = 290) were classified into 2 groups; Group 1, without gonadotropins, served as a control; Group 2, in which IVM medium was supplemented with 20 IU mL–1 equine chorionic gonadotropins (eCG). Experiment 4 was carried out to examine the suitable capacitating agent added to BO medium, either heparin or caffeine or both (n = 210 fertilized oocytes). In all experiments (multiple replicates), oocytes (2–6 mm in diameter) were kept at 39°C under 5% CO2 for IVMFC and examined several times for cleavage and embryo development (morula and blastocyst). Statistical analysis was carried out using Chi-squared test. Excellent and good quality oocytes produced a higher (P < 0.05) maturation, cleavage, and morula development rates than poor quality oocytes (70% and 65% v. 33.3%), (50% and 46.2% v. 25%), and (42.9% and 33.3% v. 10%), respectively. Blastocyst production rate was also higher (P < 0.05) for excellent compared with good quality oocytes (28.6% v. 16.7%, respectively). In experiment 2, the IVM and cleavage rates were significantly higher (P < 0.05) in IVM medium plus 10% EBS than those cultured in 10% FCS (73% v. 45% and 50% v. 33.3%, respectively). In experiment 3, the addition of eCG to maturation medium increased (P < 0.05) developmental competence of buffalo oocytes (IVMFC) compared with control medium (16% v. 4%). In experiment 4, the addition of heparin together with caffeine to BO medium produced significantly higher (P < 0.05) cleavage and embryo developmental rates compared with heparin or caffeine alone (56.3% v. 33.3% and 35.7%, respectively; 22.2% v. 10% and 8%, respectively). In conclusion, excellent quality oocytes cultured in IVM medium supplemented with either EBS or eCG and fertilized with capacitated buffalo spermatozoa in BO medium enriched with heparin and caffeine progressively enhanced developmental competence of buffalo oocytes.

scholarly journals Melatonin attenuates postovulatory oocyte dysfunction by regulating SIRT1 expression

Reproduction ◽  
2018 ◽  
Vol 156 (1) ◽  
pp. 81-92 ◽  
Author(s):  
Qingling Yang ◽  
Shanjun Dai ◽  
Xiaoyan Luo ◽  
Jing Zhu ◽  
Fangyuan Li ◽  
...  
Keyword(s):  
Aging Process ◽  
Oocyte Quality ◽  
Developmental Competence ◽  
Oocyte Aging ◽  
Sirt1 Inhibitor ◽  
Underlying Mechanisms ◽  
Related Proteins ◽  
Sirt1 Activator

The quality of postovulatory metaphase II oocytes undergoes a time-dependent deterioration as a result of the aging process. Melatonin is considered to be an anti-aging agent. However, the underlying mechanisms of how melatonin improves the quality of postovulatory aged oocytes remain largely unclear. In this study, by using mouse model, we found that there were elevated reactive oxygen species levels and impaired mitochondrial function demonstrated by reduced mitochondrial membrane potential and increased mitochondrial aggregation in oocytes aged 24 h, accompanied by an increased number of meiotic errors, unregulated autophagy-related proteins and early apoptosis, which led to decreased oocyte quality and disrupted developmental competence. However, all of these events can be largely prevented by supplementing the oocyte culture medium with 10−3 M melatonin. Additionally, we found that the expression of sirtuin family members (SIRT1, 2 and 3) was dramatically reduced in aged oocytes. In addition,in vitrosupplementation with melatonin significantly upregulated the expression of SIRT1 and antioxidant enzyme MnSOD, but this action was not observed for SIRT2 and SIRT3. Furthermore, the protective effect of melatonin on the delay of oocyte aging vanished when the SIRT1 inhibitor EX527 was used to simultaneously treat the oocytes with melatonin. Consistent with this finding, we found that the postovulatory oocyte aging process was markedly attenuated when the oocytes were treated with the SIRT1 activator SRT1720. In conclusion, our data strongly indicate that melatonin delays postovulatory mouse oocyte aging via a SIRT1–MnSOD-dependent pathway, which may provide a molecular mechanism support for the further application of melatonin in the assisted reproductive technology field.

scholarly journals ID: 1068 Effect of caffeine supplementation during in vitro maturation on development of parthenogenetic embryos derived from aging oocytes

2017 ◽  
Vol 4 (S) ◽  
pp. 150
Author(s):  
Nguyen Thi Thuy Van ◽  
Doanh Duc Nghia ◽  
Nguyen Van Thuan ◽  
Hong Thuy Bui
Keyword(s):  
Nuclear Transfer ◽  
In Vitro Maturation ◽  
Treated Group ◽  
Oocyte Quality ◽  
Blastocyst Stage ◽  
Basic Medium ◽  
Long Time ◽  
Metaphase I

“Oocyte aging” refers to degradation of oocytes which is considered as consequence of long time nuclear transfer manipulation which leads to the reduced success rate of somatic nuclear transfer (SCNT). Caffeine, which has ability of maintenance of the maturation-promoting factor (MPF) from oocyte metaphase, is considered as an improvement factor of oocyte quality. However, the influence of caffeine in aged oocytes in which duration of oocyte development is still unknown. In this study, the supplementation of caffeine during in vitro maturation of porcine embryos (from metaphase I to metaphase II) was examined on the parthenogenesis models and evaluated its effect in aged oocyte quality. After reaching metaphase I stage (27 hours) of in vitro maturation (IVM), oocytes were continuously cultured with or without 5mM caffeine until metaphase II (42 hours), then induced aging in basic medium without hormone for 6 hours before parthenogenesis activation. Results indicated that the supplementation of caffeine at metaphase I to metaphase II during in vitro maturation had significantly improved the development of embryo to four-cell, eight-cell and importantly blastocyst stage. There was noticeably significant improvement in rate and quality of blastocyst of aging oocytes treated with caffeine compared to non-treated group (39.1% and 10.3%, respectively). Furthermore, caffeine treatment can reduce the fragmentation of aging oocyte. Hence, the interpretation of caffeine supplementation during metaphase I to metaphase II could improve the quality of embryo development and quality of blastocysts developed from aging oocytes (6 hours).

scholarly journals hCG Priming Before Ovary Collection Increasing The Oocyte Quality In The Domestic Cat

2021 ◽  
pp. 123-126
Author(s):  
Karisma Mardatillah ◽  
Rini Widyastuti ◽  
Diah Nugrahani Pristihadi ◽  
Wahyudin ◽  
Sigit Prastowo ◽  
...  
Keyword(s):  
Oocyte Quality ◽  
Domestic Cat ◽  
Developmental Competence ◽  
Control Group ◽  
Oocyte Competence ◽  
Slicing Method ◽  
Determining Factor

Oocyte competence is a determining factor that influences the embryo development. Embryos produced in vitro have a reduced developmental competence than embryos produced in vivo. Therefore, human Chorionic Gonadotropin (hCG) injection was carried out to improve the quality of the oocytes. The objective of this study was to evaluate the effect of ovarian stimulation with hCG before ovary collection on oocyte quality in the domestic cat. Oocyte donors were either 1) treated with a single dose of 200 IU hCG four days before ovary collection (hCG group), or, 2) no treatment before ovary collection (control group). The oocytes were collected by the slicing method. Immature cumulus oophorus complexes (COCs) from both groups were pooled and matured in vitro for 24-26 hours. Then mature oocytes were fertilized with epididymal sperm and cultured in vitro for seven days. The results study showed that the number of the dominant follicle (DF) and the number of COCs in the hCG group was higher than the control group in right and left ovaries (p<0.05). The morulae and blastocyst rates from cleavage embryos were 88% and 75%, respectively. These results demonstrate that hCG priming of oocytes donors before ovary collection improve oocyte quality.

26 Season affects cryotolerance of in vitro-produced buffalo embryos

2019 ◽  
Vol 31 (1) ◽  
pp. 139 ◽  
Author(s):  
M. A. Kosior ◽  
E. Parente ◽  
F. Salerno ◽  
K. Annes ◽  
R. Annunziata ◽  
...  
Keyword(s):  
Developmental Stage ◽  
Breeding Season ◽  
Embryo Quality ◽  
Sucrose Solution ◽  
Oocyte Quality ◽  
Developmental Competence ◽  
Seasonal Effect ◽  
Morphological Criteria ◽  
Breeding Seasons

Buffaloes are tendentially short-day breeders, and seasonality is one of the main factors affecting the feasibility of ovum pickup and in vitro embryo production technology in this species. An improvement of oocyte developmental competence during decreasing daylight months was previously reported in Italian Mediterranean buffalo (Di Francesco et al. 2011 Anim. Reprod. Sci. 123, 48-53). The aim of this work was to evaluate whether season also affects embryo quality and cryotolerance. Abattoir-derived buffalo cumulus-oocyte complexes were collected during the breeding season, characterised by decreasing daylight length (n=349 over 6 replicates), and the non-breeding season, characterised by increasing daylight length (n=770 over 12 replicates). Buffalo cumulus-oocyte complexes were in vitro matured, fertilized, and cultured according to standard procedures (Di Francesco et al. 2011 Anim. Reprod. Sci. 123, 48-53). The embryos obtained by the end of culture (i.e. on Day 7 post-IVF) were scored for quality and developmental stage, and the percentages of total transferable embryos (tight morulae and blastocysts) were recorded. Embryos (n=107 and 110 in the breeding and non-breeding seasons, respectively) were vitrified by cryotop in 16.5% ethylene glycol, 16.5% dimethyl sulfoxide, and 0.5M sucrose (Boccia et al. 2013 Ital. J. Anim. Sci. 12, 492-496). Warming was carried out by plunging the cryotop strip into a 0.25M sucrose solution and transferring the embryos into 0.15M sucrose for 5min. Embryos were then washed and cultured in SOF for 24h to evaluate post-culture viability. The resistance to cryopreservation was evaluated by assessing the survival rate, on the basis of morphological criteria, and development rate (i.e. the percentage of embryos that resumed their development and reached a more advanced developmental stage) after 24h post-warming culture. Data were analysed by Student’s t-test. Both cleavage (82.8±4.3v. 73.1±1.7 in the breeding and non-breeding seasons, respectively; P&lt;0.05) and blastocyst (32.9±3.5v. 18.3±1.7 in the breeding and non-breeding seasons, respectively; P&lt;0.01) rates increased during the breeding season, confirming previous observations. Due to the different efficiency, a higher number of replicates was required during the non-breeding season to obtain an equal number of embryos. In addition, a seasonal effect was recorded on embryo quality, indicated by poorer cryotolerance of in vitro-produced buffalo embryos during the non-breeding season. Indeed, both survival (94.6±2.7% and 74.0±5.5% in the breeding and non-breeding seasons, respectively; P&lt;0.01) and development (67.3±7.6% and 40.0±7.2% in the breeding and non-breeding seasons, respectively; P&lt;0.01) rates of vitrified blastocysts decreased after 24h post-warming culture in the non-breeding season. These findings suggest that the reduced developmental competence of buffalo oocytes during the non-breeding season may also lead to lower blastocyst quality. This is in contrast to the evidence in cattle that embryo quality is mainly determined by culture conditions, whereas blastocyst production depends on oocyte quality.

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