Effect of environmental temperature on quality and developmental competence in vitro of buffalo oocytes

Improved the in vitro blastocyst development in oocytes recovered from cyclic buffaloes

This study examined the impact of cyclicity (with or without cycle corpus luteum; CL) on oocyte quality and embryonic development in buffaloes. We collected oocytes from the ovaries of slaughtered buffaloes (N = 158 cyclic; n = 316 ovaries and N = 177 acyclic; n = 353 ovaries). Blood progesterone concentration and number of oocytes per ovary were higher in cyclic buffaloes. Cyclic buffalo ovaries produce higher oocytes with I + II and fewer III + IV grades. Oocytes from cyclic buffaloes had a higher maturation rate based on cumulus expansion, cleavage rate and embryo development to the 8-cell, morula and blastocyst stages than acyclic buffaloes. In conclusion, oocytes recovered from the ovaries of the cyclic buffaloes showed improved oocyte competence and subsequent in vitro blastocyst development.

Administration of melatonin prior to modified synchronization protocol improves the productive and reproductive efficiency of Chinese crossbred buffaloes in low breeding season

Introduction

Melatonin is a neurohormone involving various biological processes, including restoration of cyclicity in animals with seasonal breeding patterns. The use of melatonin in different forms has gained broader acceptance in different species, particularly in summer anestrous buffaloes.

Objectives

The objective of the current study was to evaluate the melatonin effect on the reproductive and productive performance of crossbred buffaloes during the low breeding season.

Methods

Sixty-five cyclic and reproductively sound crossbred buffaloes were randomly allocated to three groups: the G1 (n = 20) served as the control group and received no single melatonin, G2 received melatonin (n = 22; 18 mg/50 kg, body weight) once prior to synchronization and G3 group was administered multiple melatonin injections (n = 23; 6 mg/50 kg body weight) for three consecutive days before the start of the synchronization protocol. The reproductive performance, milk yield traits, and serum immunoglobulin M (IgM) and melatonin levels were evaluated in treated and untreated crossbred buffaloes.

Results

The results revealed that a single dose of melatonin administration has (p < 0.05) improved estrus response, ovulation occurrence and follicular growth in crossbred buffaloes compared to control groups. Higher pregnancy rates were observed in both melatonin-treated buffalo groups compared to the control. Following the administration of melatonin, serum IgM level increased in G2 and G3; however, an increment in melatonin level (p < 0.05) was detected in the G2 group only as compared to the control group subsequent day of melatonin administration. The milk compositions were not affected by melatonin administration except for milk urea nitrogen and somatic cell count (SCC). The melatonin administration (p < 0.05) decreased the somatic cell count in buffalo milk compared to untreated.

Conclusion

In conclusion, single or multiple doses of melatonin before initiating the synchronization protocol improved the ovulation, ovulatory follicle diameter and pregnancy rates in crossbred buffaloes during the low breeding season. Moreover, the administration of melatonin enhanced the IgM values along milk traits in terms of milk protein, MUN and somatic cell count in treated buffaloes.

Responses of Dairy Buffalo to Heat Stress Conditions and Mitigation Strategies: A Review

Increases in temperature and the greater incidence of extreme events are the consequences of the climate change that is taking place on planet Earth. High temperatures create severe discomfort to animal farms as they are unable to efficiently dissipate their body heat, and for this, they implement mechanisms to reduce the production of endogenous heat (reducing feed intake and production). In tropical and subtropical countries, where buffalo breeding is more widespread, there are strong negative consequences of heat stress (HS) on the production and quality of milk, reproduction, and health. The increase in ambient temperature is also affecting temperate countries in which buffalo farms are starting to highlight problems due to HS. To counteract HS, it is possible to improve buffalo thermotolerance by using a genetic approach, but even if it is essential, it is a long process. Two other mitigation approaches are nutritional strategies, such as the use of vitamins, minerals, and antioxidants and cooling strategies such as shade, fans, sprinklers, and pools. Among the cooling systems that have been evaluated, wallowing or a combination of fans and sprinklers, when wallowing is not available, are good strategies, even if wallowing was the best because it improved the production and reproduction performance and the level of general well-being of the animals.

Seasonality and photoperiod influence in vitro production of buffalo embryos

Buffalo is considered short-day breeder in tropical and subtropical part of the world and seasonality and photoperiodism impart major influence on its fertility. However, its impact on in vitro embryo production (IVEP) remains elusive. Therefore, this study investigated the effect of seasonal variations and photoperiodism on morphological and molecular parameters of IVEP in buffalo. For this purpose, we conducted two different experiments on the oocytes obtained by aspirating follicles from abattoir derived ovaries. In Exp. I, retrospective analysis was performed for oocyte recovery, blastocyst and hatching rate, during four consecutive seasonal periods (i.e. January-March, April-June, July-September and October-December). In Exp. II, oocytes from peak breeding and non-breeding seasons were subjected to 24 hr in vitro maturation and evaluated for polar body extrusion to assess maturation rate. Results showed that embryo development was markedly low during second quarter (April-June) and maximum during fourth quarter (October-December) of the year; referred as non-breeding and breeding seasons, respectively. Comparative data analysis demonstrated that poor oocyte quality is major reason for lesser efficiency of embryo production during non-breeding season than peak breeding season as suggested by poor oocyte recovery (2.31 ± 0.10 vs. 3.65 ± 0.27) and maturation rate (33.32 ± 2.1 vs. 63.15 ± 7.31). Subsequently, comparative gene expression analysis of blastocysts during peak breeding season significantly upregulated pluripotency gene (OCT-4) and downregulated heat shock protein 90, as compared to non-breeding season. Therefore, it could be divulged from the present study that seasonal variations and photoperiodism have profound effect on oocyte quality and subsequent embryo development. It is recommended to find suitable additives for in vitro maturation that could mitigate seasonal effects.

Effect of season on the in-vitro maturation and developmental competence of buffalo oocytes after somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is a valuable technology tool with various uses in transgenic animals, regenerative medicine, and stem cell research. However, the efficiency of SCNT embryos appears to have poor developmental competency. Environmental issues may adversely affect SCNT embryos in buffalo. Thereafter, the present study aimed to explore the effect of season on the maturation of buffalo oocytes and subsequent developmental capability after parthenogenetic activation and SCNT in buffalo. Buffalo oocytes (n = 6353) were collected from local slaughterhouse at various seasons; spring (March-April), summer (May-August), autumn (September-November), and winter (December-January). A significant increase (p < 0.05) was recorded in the maturation rate (57.07%) at autumn compared with spring, summer, and winter (50.46, 50.93, and 50.66%, respectively). No significant differences were recorded in the fusion and the cleavage rates among all seasons. Blastocyst development rate was higher (p < 0.05) in autumn and winter (16.52 ± 8.45% and 15.98 ± 7.17%, respectively) than in spring and summer (9.47 ± 6.71% and 10.84 ± 6.58%, respectively) seasons. It could be concluded that the season had a significant effect on oocyte development competence which can be used for SCNT in buffalo.

Effects of reproductive season on embryo development in the buffalo

Interest in buffalo farming is increasing worldwide due to the critical role played by buffaloes as sources of animal protein in tropical and subtropical environments. However, reproductive seasonality negatively affects the profitability of buffalo farming. Buffaloes tend to be short-day breeders, with seasonality patterns increasing with greater distances from the Equator. Although ovarian cyclic activity may occur throughout the year, seasonal anoestrus and cycles in calving and milk production are recorded. When buffaloes are forced to mate during the unfavourable season, to meet market demand, they may undergo a higher incidence of embryo mortality. This review addresses the effects of the reproductive season on embryo development in the buffalo, analysing the different factors involved in determining embryo mortality during the unfavourable season, such as impaired luteal function, oocyte competence and sperm quality. The review then focuses on strategies to control the photoperiod-dependent annual fluctuations in conception and embryo mortality in the female buffalo.

Developmental and molecular responses of buffalo (Bubalus bubalis) cumulus–oocyte complex maturedin vitrounder heat shock conditions

To investigate the effects of physiologically relevant heat shock during oocyte maturation, buffalo cumulus–oocyte complexes (COCs) were cultured at 38.5°C (control) or were exposed to 39.5°C (T1) or 40.5°C (T2) for the first 6 h ofin vitromaturation (IVM), followed by 38.5°C through the next 18 h/IVM and early embryonic development up to the blastocyst stage. Gene expression analysis was performed on selected target genes (HSF-1,HSF-2,HSP-70,HSP-90,BAX,p53,SOD1,COX1,MAPK14) in denuded oocytes and their isolated cumulus cells resulting from control COCs as well as from COCs exposed to a temperature of 39.5°C (T1). The results indicated that heat shock significantly (P< 0.01) decreased the maturation rate in T1 and T2 cells compared with the control. Afterin vitrofertilization (IVF), cleavage rate was lower (P< 0.01) for oocytes exposed to heat stress, and the percentage of oocytes arrested at the 2- or 4-cell stage was higher (P< 0.01) than that of the control. The percentage of oocytes that developed to the 8-cell, 16-cell or blastocyst stage was lower (P< 0.01) in both T1 and T2 groups compared with the control group. mRNA expression levels for the studied genes were decreased (P< 0.05) in treated oocytes (T1) except forHSP-90andHSF-1, which were increased. In cumulus cells isolated from COCs (T1), the expression for the target genes was upregulated except forBAX, which was downregulated. The results of this study demonstrated that exposure of buffalo oocytes to elevated temperatures for 6 h severely compromised their developmental competence and gene expression.

Developmental competence and expression profile of genes in buffalo (Bubalus bubalis) oocytes and embryos collected under different environmental stress

The study examined the effects of different environmental stress on developmental competence and the relative abundance (RA) of various gene transcripts in oocytes and embryos of buffalo. Oocytes collected during cold period (CP) and hot period (HP) were matured, fertilized and cultured in vitro to blastocyst hatching stage. The mRNA expression patterns of genes implicated in developmental competence (OCT-4, IGF-2R and GDF-9), heat shock (HSP-70.1), oxidative stress (MnSOD), metabolism (GLUT-1), pro-apoptosis (BAX) and anti-apoptosis (BCL-2) were evaluated in immature and matured oocytes as well as in pre-implantation stage embryos. Oocytes reaching MII stage, cleavage rates, blastocyst yield and hatching rates increased (P < 0.05) during the CP. In MII oocytes and 2-cell embryos, the RA of OCT-4, IGF-2R, GDF-9, MnSOD and GLUT-1 decreased (P < 0.05) during the HP. In 4-cell embryos, the RA of OCT-4, IGF-2R and BCL-2 decreased (P < 0.05) in the HP, whereas GDF-9 increased (P < 0.05). In 8-to 16-cell embryos, the RA of OCT-4 and BCL-2 decreased (P < 0. 05) in the HP, whereas HSP-70.1 and BAX expression increased (P < 0.05). In morula and blastocyst, the RA of OCT-4, IGF-2R and MnSOD decreased (P < 0.05) during the HP, whereas HSP-70.1 was increased (P < 0.05). In conclusion, deleterious seasonal effects induced at the GV-stage carry-over to subsequent embryonic developmental stages and compromise oocyte developmental competence and quality of developed blastocysts.

Developmental competence and expression pattern of bubaline (Bubalus bubalis) oocytes subjected to elevated temperatures during meiotic maturation in vitro

OBJECTIVE

To determine the direct effect of physiologically relevant high temperatures (40.5 and 41.5 °C) for two time periods (12 and 24 h) on bubaline oocytes during in vitro maturation.

METHOD

The control group oocytes were cultured at 38.5 °C for 24 h. The treatment 1 (T1) and 3 (T3) group oocytes were cultured at 40.5 and 41.5 °C respectively, for the first 12 h and at 38.5 °C for rest of the 12 h. However, treatment 2 (T2) and 4 (T4) group oocytes were cultured at 40.5 and 41.5 °C for complete 24 h.

RESULTS

Development of oocytes to blastocyst was severely compromised (p < 0.001) when matured at 40.5 and 41.5 °C for both exposure periods (12 h and 24 h). It was found that the cleavage rates, blastocyst yield and mean cell number decreased remarkably (p < 0.001) in the treatment groups compared to control. The relative mRNA expression of heat shock protein (Hsp 70.1, 70.2, 70.8, 60, 10 and HSF1), pro-apoptotic (caspases-3, -7, -8, Bid and Bax) and oxidative stress (iNOS) related genes was significantly higher (p < 0.05) in all the treatment groups compared to control. However, mRNA abundance of anti-apoptotic (Bcl-2, Mcl-1, Bcl-xl), glucose transport (Glut1, Glut3 and IGF1R), developmental competence (ZAR1 and BMP15) and oxidative stress (MnSOD) related genes was significantly decreased (p < 0.05) in the treatment groups compared to control.

CONCLUSION

The present study clearly establishes that physiologically relevant elevated temperatures during in vitro meiotic maturation reduce developmental competence of bubaline oocytes.

Reference gene selection for gene expression analysis of oocytes collected from dairy cattle and buffaloes during winter and summer

Oocytes from dairy cattle and buffaloes have severely compromised developmental competence during summer. While analysis of gene expression is a powerful technique for understanding the factors affecting developmental hindrance in oocytes, analysis by real-time reverse transcription PCR (RT-PCR) relies on the correct normalization by reference genes showing stable expression. Furthermore, several studies have found that genes commonly used as reference standards do not behave as expected depending on cell type and experimental design. Hence, it is recommended to evaluate expression stability of candidate reference genes for a specific experimental condition before employing them as internal controls. In acknowledgment of the importance of seasonal effects on oocyte gene expression, the aim of this study was to evaluate the stability of expression levels of ten well-known reference genes (ACTB, GAPDH, GUSB, HIST1H2AG, HPRT1, PPIA, RPL15, SDHA, TBP and YWHAZ) using oocytes collected from different categories of dairy cattle and buffaloes during winter and summer. A normalization factor was provided for cattle (RPL15, PPIA and GUSB) and buffaloes (YWHAZ, GUSB and GAPDH) based on the expression of the three most stable reference genes in each species. Normalization of non-reference target genes by these reference genes was shown to be considerably different from normalization by less stable reference genes, further highlighting the need for careful selection of internal controls. Therefore, due to the high variability of reference genes among experimental groups, we conclude that data normalized by internal controls can be misleading and should be compared to not normalized data or to data normalized by an external control in order to better interpret the biological relevance of gene expression analysis.

Expression pattern of pluripotent markers in different embryonic developmental stages of buffalo (Bubalus bubalis) embryos and putative embryonic stem cells generated by parthenogenetic activation

In this study, we describe the production of buffalo parthenogenetic blastocysts and subsequent isolation of parthenogenetic embryonic stem cell (PGESC)-like cells. PGESC colonies exhibited dome-shaped morphology and were clearly distinguishable from the feeder layer cells. Different stages of development of parthenogenetic embryos and derived embryonic stem cell (ESC)-like cells expressed key ESC-specific markers, including OCT-4, NANOG, SOX-2, FOXD3, REX-1, STAT-3, TELOMERASE, NUCLEOSTEMIN, and cMYC. Immunofluorescence-based studies revealed that the PGESCs were positive for surface-based pluripotent markers, viz., SSEA-3, SSEA-4, TRA 1-80, TRA 1-60, CD-9, and CD-90 and exhibited high alkaline phosphatase (ALP) activity. PGEC cell-like cells formed embryoid body (EB)-like structures in hanging drop cultures and when cultured for extended period of time spontaneously differentiated into derivatives of three embryonic germ layers as confirmed by RT-PCR for ectodermal (CYTOKERATIN8, NF-68), mesodermal (MSX1, BMP-4, ASA), and endodermal markers (AFP, HNF-4, GATA-4). Differentiation of PGESCs toward the neuronal lineage was successfully directed by supplementation of serum-containing media with retinoic acid. Our results indicate that the isolated ESC-like cells from parthenogenetic blastocyst hold properties of ESCs and express markers of pluripotency. The pluripotency markers were also expressed by early cleavage-stage of buffalo embryos.

Effect of the stage of estrous cycle on follicular population, oocyte yield and quality, and biochemical composition of serum and follicular fluid in Anatolian water buffalo

This study was designed to investigate the effects that the different stages of the estrous cycle had on the number of surface ovarian follicles and oocyte yield and quality of Anatolian water buffalo during peak breeding season. Assessments were made on the basis of ovarian morphology, serum and follicular fluid concentrations of variety of biochemical parameters. Following slaughter, blood samples were collected from each animal. The stage of estrous cycle was classified as either the luteal or follicular phase, and surface ovarian follicles were classified as small, medium, or large. The follicular fluid was aspirated, and oocytes were evaluated microscopically for classification into four categories. No statistical differences (p>0.05) were observed regarding the total number of follicles or quality of oocytes relative to the stage of the estrous cycle. Serum high-density lipoprotein cholesterol (HDL), alkaline phosphatase (ALP) and progesterone (P4) concentrations were significantly higher in the luteal phase than in the follicular phase (P<0.05). Significant correlations were observed in the luteal phase between the total number of oocytes and cholesterol (Cho), HDL, sodium (Na), chloride (Cl); A-quality oocytes and Na, Cl, Mg; C-quality oocytes and Cho, HDL, and Mg in follicular fluid. These results offer new information concerning Anatolian water buffalo reproductive physiology, which may be useful for improving oocyte quality in buffalo. This is the first study to describe the number of ovarian follicles, oocyte yield and quality, and a variety of biochemical parameters in the serum and follicular fluid of Anatolian water buffalo during peak breeding season in Turkey.

Equivalency of buffalo (Bubalus bubalis) embryonic stem cells derived from fertilized, parthenogenetic, and hand-made cloned embryos

This study was aimed at establishing buffalo embryonic stem cells (ESCs) from in vitro fertilized (IVF), parthenogenetic, and hand-made cloned (HMC) embryos and to check their equivalency in terms of stem cell marker expression, longevity, proliferation, and differentiation pattern. ESCs derived from all three sources were found by immunofluorescence to express the pluripotency markers SSEA-4, TRA-1-60, TRA-1-81, OCT4, and SOX2 and were able to form embryoid bodies containing cells expressing genes specific to endoderm (AFP, HNF4, and GATA4), mesoderm (MSX1, BMP4, and ASA), and ectoderm (cytokeratin 8 and NF68). Reverse transcriptase PCR (RT-PCR) showed cells from all sources to be positive for pluripotency markers OCT4, SOX2, NANOG, STAT3, REX1, FOXD3, NUCLEOSTEMIN, and TELOMERASE. Pluripotency markers OCT4, SOX2, NANOG, and c-MYC were also analyzed by real-time PCR. No significant differences were observed among ESCs from all three sources for all these genes except NANOG, whose expression was higher (p<0.05) in HMC-derived ESCs (6.897±2.3) compared to that in parthenogenesis- and IVF-derived cells (1.603±0.315 and 1±0, respectively). Pluripotent, stable buffalo ESC lines derived from IVF, parthenogenesis, and HMC embryos may be genetically manipulated to provide a powerful tool for studies involving embryonic development, genomic imprinting, gene targeting, cloning, chimera formation, and transgenic animal production.

The effect of season on oocyte quality and developmental competence in Italian Mediterranean buffaloes (Bubalus bubalis)

At Italian latitudes, buffalo (Bubalus bubalis) is a seasonally polyestrous species, showing an improved reproductive efficiency when daylight decreases (autumn). The aim of the present study was to evaluate the influence of the season on buffalo oocyte recovery rate, on oocyte quality, assessed on morphological basis, and developmental competence after in vitro fertilization. For this purpose, buffalo ovaries were collected from a local abattoir and the oocytes obtained by aspirating the follicles were evaluated, classified and, if considered of good quality, devolved to the different procedures of IVEP. In general, no differences were found in terms of oocyte recovery per ovary among seasons, but interestingly, the percentage of small oocytes was higher (P<0.05) during spring and summer (0.9±0.1 and 0.9±0.2) compared to autumn and winter (0.3±0.1 and 0.2±0.1). Both cleavage and embryo rate increased during the period from October to December (71.7±3.1 and 26.5±2.1, respectively) compared to the period from April to June (58.0±2.4 and 18.8±1.6, respectively), thus reflecting the in vivo reproductive behavior. Nevertheless, it is worth emphasizing that transferrable embryos were produced in vitro, even during the unfavorable season, but with decreased efficiency. In conclusion, these results suggest to avoid the oocyte collection during spring when planning OPU trials in order to save resources and improve the benefits/costs ratio.

Factors affecting laboratory production of buffalo embryos: a meta-analysis

In vitro fertilization (IVF) provides an excellent and inexpensive source of embryos for carrying out basic research on developmental physiology, farm animal breeding, and for commercial applications. Meta-analysis of the results from different publications rather than a narrative review may provide a current status of this technology in buffalo (Bubalus bubalis). In order to gain an idea of the factors affecting the IVF in buffalo, a review of the various studies conducted on buffalo IVF and a meta-analysis of their findings was undertaken. More than 100 articles published from 1991 to 2008 were searched, and results were subjected to meta-analysis to determine the treatment variations without any bias. Thirty factors affecting in vitro embryo production in buffalo were considered. Initially, both fixed- and random-effect models were used. We did not observe any heterogeneity between the studies. Thereafter, all the studies were pooled using the fixed-effect model for analysis. Our analysis suggested that good buffalo oocytes with more than three to five cumulus layers recovered from large-sized follicles in cold seasons when cultured in TCM-199 supplemented with serum, follicle-stimulating hormone, and cysteamine resulted in maximum maturation rate and subsequent embryonic development after insemination. The values obtained in the current study may be considered for a simulation model in establishing a cost-effective suitable method for buffalo IVF in further planned research.

Some studies on the morphological aspects of buffalo oocytes in relation to the ovarian morphology and culture condition

The present study was conducted to establish the effects of ovarian morphology on oocyte quantity and quality, as well as the effect of preincubated granulosa cells (PGCs) on in vitro maturation of buffalo oocytes and steroid hormones production. A total of 52 ovarian pairs were grouped into three types: type I (with functional corpus luteum), type II (with regressed corpus luteum), and type III (without corpus luteum). The number of follicles and oocytes/ovary were documented. The follicles were classified into three groups (<2, 2-6, and >6 mm Ø). Oocytes were classified according to their morphology into four grades (grades A, B, C, and D), or according to their cumulus compactness into four groups (more than three layers, one to three layers of cumulus cells, partial remnants of cumulus cells, and no cumulus cells). A PGCs was used to investigate their steroidogenic potential on the in vitro maturation. The highest number of follicles and oocytes was found in type III than types II and I. Grades A and B oocytes were significantly higher (P < 0.01) in number in type III ovaries. Oocytes with more than three layers of cumulus cells showed higher maturation rate than oocytes with partial remnants or no cumulus cells but with small difference from oocytes having one to three layers of cumulus cells. Beside the higher maturation rate in compact than denuded oocytes, a significantly higher (P < 0.01) rates obtained in compact or denuded oocytes when cultured in vitro with PGCs than the corresponding oocytes with no PGCs. These maturation rates coincided with higher level (P < 0.05) of estradiol-17ss when compact oocytes cultured with or without PGCs than denuded oocytes and higher level (P < 0.05) of progesterone after culture with PGCs for both compact and denuded oocytes than the corresponding oocytes with no PGCs. In summary, buffalo ovaries with no corpus luteum may be suggested for obtaining high number of follicles and good oocytes than the others. Oocytes with intact cumulus showed better maturation than those with partial or denuded cumulus, although the denuded oocytes improved their meiotic competence to a less or greater extent when cultured in vitro with PGCs.

Effect of breeding season on in vivo oocyte recovery and embryo production in non-descriptive Indian river buffaloes (Bubalus bubalis)

The present study was carried out to examine the effect of season on in vivo oocyte recovery and embryo production in non-descriptive, Indian river buffaloes (Bubalus bubalis). Ovum pick up (OPU) was conducted twice a week for 8 weeks during peak (October-March) and low (April-September) breeding season in live buffaloes (n=6). OPU was performed using ultrasound equipment with a 5MHz transvaginal transducer, a single lumen 18-gauge, 55-cm long needle and a constant vacuum pressure of 110mmHg. The number and size of follicles was determined before puncture. The recovered oocytes were graded and only grade A and grade B oocytes were used for in vitro production (IVP) of embryos. The mean number of follicles observed per animal per session did not differed (P<0.05) between animals or between puncture sessions in both low and peak breeding seasons. Higher (P<0.05) number of follicles were observed (4.8+/-0.2 versus 3.1+/-0.3) and punctured (4.0+/-0.2 versus 2.4+/-0.2) during peak breeding season when compared to low breeding season. Oocytes recovered (1.6+/-0.1 versus 1.0+/-0.3) per animal per session were higher (P<0.05) in peak breeding season than low breeding season. During the peak breeding season, the blastocyst yield per animal per session (0.3+/-0.4 versus 0.18+/-0.4) was higher (P<0.05) than the low breeding season. However, season did not significantly affect the percentage of oocytes suitable for IVP (grade A+B) and blastocyst production rate. In conclusion, the efficiency of OPU combined with IVP was higher during the peak breeding season than the low breeding season in buffaloes.

Nuclear morphology, diameter and meiotic competence of buffalo oocytes relative to follicle size

The nuclear morphology, diameter and in vitro meiotic competence of buffalo oocytes was compared relative to follicle size. Cumulus-oocyte complexes (COCs) were collected from 1-<2, 2-<3, 3-<4, 4-<6 and 6-<8 mm follicles from abattoir ovaries. Cumulus cells were removed using 3 mg mL(-1) hyaluronidase in saline and repeated pipetting. Denuded oocytes were measured, fixed in 3% glutaraldehyde, stained with 4,6-diamidoino-2-phenylindole and evaluated for nuclear morphology, namely the stage of germinal vesicle (GV) development before in vitro maturation (IVM). The COCs from >2-mm follicles were matured in vitro in their respective size groups for 24 h in Medium 199 supplemented with 10 microg mL(-1) follicle-stimulating hormone, 10 microg mL(-1) luteinizing hormone, 1.5 microg mL(-1) oestradiol, 75 microg mL(-1) streptomycin, 100 IU mL(-1) penicillin, 10 mM HEPES and 10% fetal bovine serum. Matured oocytes were fixed, stained and evaluated for GV status and meiotic development. The number of oocytes collected from follicles 1-<8 mm in diameter averaged 1.82 per ovary. Oocytes from follicles 1-<2 mm (107.7 +/- 1.6 microm), 2-<3 mm (108 +/- 1.1 microm) and 3-<4 mm (114.6 +/- 1.3 microm) in diameter were smaller in diameter (P < 0.05) than oocytes from follicles 4-<6 mm (124.4 +/- 1.3 microm) and 6-<8 mm (131.9 +/- 1.4 microm) in diameter. A majority of oocytes (P< 0.05) from <4-mm follicles was at the initial stages of GV development (GV-I, II and III), whereas oocytes from 4-<6- and 6-<8-mm follicles were at the final stages of GV-IV (35.0 and 21.6% respectively) and GV-V (49.1 and 67.5% respectively). Poor IVM rates of 32.0% and 32.7% to metaphase (M)-II were observed for oocytes isolated from 2-<3- and 3-<4-mm follicles, respectively, whereas significantly (P< 0.05) more oocytes from 4-<6- and 6-<8-mm follicles reached M-II (67.1% and 79.1% respectively). In conclusion, buffalo oocytes displayed a size-dependent ability to undergo meiotic maturation and we suggest that oocytes from >4-mm follicles should be considered in buffalo in vitro fertilization systems for better results.

Effect of ambient temperature on in vitro fertilization of Bubaline oocyte

The present study was used to examine the effect of ambient temperature on the day of slaughter of buffaloes on oocyte cleavage and subsequent embryo development following in vitro fertilization (IVF)/chemical activation (parthenogenesis). A total of 601 oocytes were collected from buffaloes, which were sacrificed when the ambient temperature was >40 or < or =40 degrees C and the collected oocytes were matured in vitro. During each experiment about half of the matured oocytes were used for IVF whereas the remaining oocytes were subjected to one of the three chemical activation protocols viz. (i) 7% ethanol (ET) and 6-di methyl amino purine (6-DMAP), (ii) ET and cycloheximide (CHX) and (iii) ET followed by a combined treatment of 6-DMAP and CHX. Cleaved oocytes were cultured in mSOF supplemented with BSA, essential amino acids, non-essential amino acids, ITS (insulin transferrin and selenium) and L-glutamine. Low cleavage and subsequent embryo development was observed in those oocytes which were collected from buffaloes slaughtered at ambient temperature >40 degrees C than at < or =40 degrees C. There was no significant difference in cleavage rate following different chemical activations in oocytes collected from buffaloes slaughtered on the day when the maximum ambient temperature was >40 degrees C or < or =40 degrees C. These results suggest that high ambient temperature influences competence of oocytes to cleave and develop to blastocyst stage following natural activation with sperm and/or process of fertilization and subsequent embryo development.

In vitro maturation and fertilization of buffalo oocytes: effects of storage of ovaries, IVM temperatures, storage of processed sperm and fertilization media

Studies were conducted to examine the possibility of preserving slaughterhouse-derived buffalo ovaries at 4 degrees C for 0 (control), 12 and 24 h to maintain the developmental competence of the oocytes (experiment 1), to assess the effect of incubation temperature during oocyte maturation on rates of in vitro maturation (IVM) and in vitro fertilization (IVF) of buffalo oocytes and embryo development (experiment 2), and to examine the effect of storage at 25 degrees C for 0 (control), 4 and 8 h of frozen-thawed buffalo sperm and BO and H-TALP as sperm processing and fertilization media on cleavage and embryo development in vitro of buffalo oocytes (experiment 3) in order to optimize the IVF technology in buffalo. Results suggested that storage of ovaries at 4 degrees C for 12 or 24 h significantly (p < 0.05) reduced the developmental potential of oocytes. Incubation temperatures during the IVM influenced the fertilization rate but had no significant effect on maturation and subsequent embryo development. The incubation temperature of 38.5 degrees C during IVM was found to be optimum for embryo production in vitro. Storage of frozen-thawed sperm at 25 degrees C for 8 h significantly (p < 0.05) decreased its ability to cleave the oocytes. Sperm processed in BO medium had significantly (p < 0.05) higher ability to cleave the oocytes than the H-TALP medium.

Effect of insulin, transferrin and selenium and epidermal growth factor on development of buffalo oocytes to the blastocyst stage in vitro in serum-free, semidefined media

The in vitro development of buffalo oocytes up to the blastocyst stage was studied in serum-free, semidefined media containing bovine serum albumin, follicle-stimulating hormone (FSH), insulin, transferrin and selenium (ITS) and epidermal growth factor (EGF). In experiment 1, oocytes aspirated from abattoir-derived ovaries were cultured in eight serum-free, semidefined culture media containing different combinations of these four factors. In experiment 2, the maturation of buffalo oocytes and the development of the embryos were compared in a complex co-culture system and in the serum-free, semidefined media. Supplementation with FSH and EGF significantly (P < 0.05) increased the maturation rates of buffalo oocytes, and the yield of blastocysts was higher (P < 0.05) in media containing EGF and ITS. The yield of blastocysts was lower in the serum-free semidefined media (P < 0.05) than in the complex co-culture system.

Production of buffalo (Bubalus bubalis) embryos in vitro: premises and promises

Techniques for in vitro production (IVP) of buffalo embryos adopting the procedures developed in cattle have received increasing interest in the recent times. A high oocyte maturation, fertilization and cleavage rate and a low rate of blastocyst yield and calving following transfer of in vitro produced buffalo embryos have been obtained. The efficiency of IVP in buffalo is much lower than that in cattle. Several problems need to be resolved before IVP technology can be used regularly in buffalo breeding. This review attempts to present an overview of the different techniques used in buffalo to produce transferable embryos in vitro, namely in vitro maturation and fertilization of immature oocytes and in vitro development of the resulting cleaved embryos to the blastocyst stage before transfer. The problems associated with IVP, the possible solutions and the new biotechniques linked to IVP are discussed.