In vitro maturation and fertilization of buffalo oocytes (): Effects of media, hormones and sera

Review: Development, adoption, and impact of assisted reproduction in domestic buffaloes

The domestic buffalo (Bubalus bubalis), also known as water buffalo, comprises two sub-species the River buffalo (B. bubalis ssp. bubalis; 50 chromosomes) and the Swamp buffalo (ssp. carabanensis; 48 chromosomes). Domestic buffaloes are a globally significant livestock species. In South Asia, the River buffalo is a primary source of milk and meat and has a very important role in food security. The River buffalo also supports high-value, differentiated food production in Europe and the Americas. The Swamp buffalo is an important draft animal and a source of food in Southeast Asia and East Asia. The growing importance of buffaloes requires that they undergo an accelerated rate of genetic gain for efficiency of production, product quality, and sustainability. This will involve the increased use of assisted reproduction. The initial application of reproductive technology in buffaloes had variable success as it relied on the adoption of procedures developed for cattle. This included artificial insemination (AI), sperm cryopreservation, and embryo technologies such as cloning and in vitro embryo production (IVEP). Reproductive technology has been progressively refined in buffaloes, and today, the success of AI and IVEP is comparable to cattle. Ovarian follicular superstimulation (superovulation) combined with in vivo embryo production results in low embryo recovery in buffaloes and has limited practical application. The contribution of elite female buffaloes to future genetic improvement will therefore rely mainly on oocyte pickup and IVEP. This will include IVEP from females before puberty to reduce generation intervals. This review provides for the first time a clear chronology on the development, adoption, and impact, of assisted reproduction in domestic buffaloes.

Effects of estradiol on in vitro maturation of buffalo and goat oocytes

PURPOSE

The effects of estradiol on oocyte development seem to be varied among species. The present study investigated the effects of 17β-estradiol on in vitro maturation of buffalo and goat oocytes.

METHODS

Cumulus oocyte complexes (COCs) were aspirated from large antral follicles of slaughtered buffalo and goat ovaries. COCs were cultured in TCM-199 medium supplemented with 0, 0.5, 1, and 1.5 µg/mL of 17β-estradiol for in vitro maturation. Then, oocytes were used for the examination of state of nuclear maturation and cumulus expansion.

RESULTS

In both species, oocytes treated with 17β-estradiol showed higher cumulus expansion rate than control (0 µg/mL treated). In buffalo, the percentage of oocytes matured to the metaphase II (MII) stage increased in the concentration-dependent manner of 17β-estradiol. Similarly, estradiol positively influenced nuclear maturation of goat oocytes in vitro.

CONCLUSIONS

Estradiol has promoting effects on normalprogress of in vitro oocyte meiosis in buffalos and goats.

A comparison of three methods of recovery of goat oocytes for in vitro maturation and feritilization

Experiments were conducted to determine an efficient method for recovering a large number of usable oocytes and its effect on subsequent in vitro maturation, fertilization and development. Follicular oocytes were recovered from goat ovaries using 3 different methods: aspiration, puncturing and slicing. The average total number of oocytes recovered per ovary was significantly higher by the aspiration method (2.7+/-0.15) than by puncturing (2.2+/-0.13) or by slicing (2.4+/-0.12). However, significantly more good-quality usable oocytes enclosed with compact cumulus cells were obtained by slicing (0.9+/-0.06) than by aspiration (0.5+/-0.07) or by puncturing (0.5+0.06). Time required for processing each ovary by the slicing method was comparatively less (0.90 min) than that required for puncturing (1.83 min) or for aspiration (1.78 min). Usable oocytes recovered by all three methods were matured, fertilized and developed to the blastocyst stage in vitro. There were no significant differences in the subsequent percentages of oocytes maturing, being fertilized and developing in vitro among the 3 methods of recovering oocytes. In conclusion, the recovery of goat oocytes by the slicing method is simple and efficient compared with the aspiration and puncturing methods.

In vitro maturation and fertilization of prepubertal and pubertal black Bengal goat oocytes

Oocytes retrieval, in vitro maturation (IVM) and fertilization (IVF) efficiency are inevitable steps towards in vitro production of embryos. In the present study, these parameters were investigated in the ovaries of prepubertal (n = 31) and pubertal (n = 61) black Bengal goats obtained from a slaughterhouse. Nuclear maturation was evaluated upon aspiration and following IVM in TCM-199 (Earle's salt with L-glutamine and sodium bicarbonate) for 27 h at 39℃ under 5% CO₂ in humidified air. The oocytes retrieval and efficiency (mean ± SD) per prepubertal and pubertal goats were 5.2 ± 0.6 and 6.8 ± 0.6, and 77.3 ± 0.1% and 80.5 ± 0.6%, respectively. Anaphase I - telophase I stages differed significantly (7.3 ± 0.8 vs. 2.6 ± 0.2, p < 0.05) between the two groups of goats. After IVM, the percentages of metaphase II were significantly higher (66.3 vs. 60.3, p < 0.05) in pubertal goats than in their prepubertal counterparts. The percentages of normal in vitro fertilization (IVF) in Fert-Tyrode's albumin lactate pyruvate of pubertal goat oocytes did not differ between Percoll and swim-up sperm separation methods (36.7 ± 0.9% vs. 32.7 ± 1.3%, p > 0.05). Furthermore, sperm capacitation by heparin alone or in combination with ionomycin did not lead to a significant increase in the normal fertilization rate (34.8 ± 1.7 vs. 32.2 ± 1.5%, respectively) in the oocytes of pubertal goats. In conclusion, the ovaries of pubertal black Bengal goats obtained from the slaughterhouse could be used for in vitro embryo production. However, further optimization of the IVM and IVF techniques are necessary for satisfactory in vitro embryo production.

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.

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.

Influence of epidermal growth factor and insulin-like growth factor 1 on nuclear maturation and fertilization of buffalo cumulus oocyte complexes in serum free media and their subsequent development in vitro

The in vitro maturation, fertilization and development of Indian water buffalo (Bubalus sp.) cumulus oocyte complexes (COCs) to blastocysts were studied during culture, either in serum free tissue culture medium 199 (TCM 199) or Waymouth MB (WM). Based on different supplements added to these media, the experimental groups included: (a) no supplement (control); (b) hormones (FSH, LH and oestradiol) (c) Epidermal growth factor (EGF); (d) IGF-1; and (e) EGF + IGF-1. Experiments were conducted to note three end points: (1) nuclear maturation 24 h after culture (eight replicates); (2) fertilization 24 h after insemination (10 replicates); (3) development to blastocysts (nine replicates). The oocytes were cultured in groups of up to five per drop. Using a two-way (5 x 2) factorial model with interactions, the results were compared using generalized linear models with binomial errors and the logit link function. In experiment 1, the proportion of oocytes reaching metaphase II was higher for all the supplement treatments than the control treatment (t = 3.68, p < 0.0001). The proportion of oocytes reaching metaphase II was 74.7, 63.2, 64.7 and 81% with hormone (chi2 = 17.23, p < 0.0001), EGF (chi2 = 7.07, p = 0.007), IGF-1 (chi2 = 19.21, p = 0.002) and EGF + IGF-1 (chi2 = 33.04, p < 0.0001) supplementation, respectively, compared to 46.6% in the control (no supplement) group. Media did not have an effect on outcome. In experiment 2, the proportion of oocytes fertilized was significantly higher with hormones (31.0%, chi2 = 12.5, p = 0.0004), IGF-1 (35.7%, chi2 = 20.53, p < 0.0001), and the EGF + IGF-1 combination (49.7%, chi2 = 51.35, p < 0.0001) compared to control (16.2%). No significant effect of media was seen. In experiment 3, the proportion of oocytes that cleaved at 48 h after culturing was significantly higher for all supplement treatments compared to control. IGF-1 supplementation was the only treatment that did not produce a significantly higher rate of progression to blastocysts compared to the control. Once again, media had no effect on outcome. It was concluded that maturation, fertilization and development of buffalo oocytes were enhanced by all supplements tested. Enhancement was maximal with the combination of EGF+IGF-1. In contrast, no significant differences were found between the two types of media used.

Post-warming hatching and birth of live calves following transfer of in vitro-derived vitrified water buffalo (Bubalus bubalis) embryos

Viability of in vitro-derived vitrified-warmed preimplantation stage buffalo embryos were assessed in vitro and in vivo. Oocytes were collected from ovaries of slaughtered riverine buffaloes, matured and fertilized in vitro with frozen semen from riverine buffalo bull and cultured on cumulus cell monolayers. Resultant preimplantation stage embryos were cryopreserved by vitrification with ethylene glycol, ficoll and sucrose. Seventy-one frozen embryos were warmed in 0.5M sucrose and were further cultured in vitro for 72 h to assess hatching rate. On the other hand, 95 embryos were transferred non-surgically to riverine buffalo recipients to assess development competence in vivo through detection of pregnancy and birth of live calves. Hatching rate of 83.10% (59/71) was noted among embryos cultured in vitro. Pregnancy rate was 16.36% (9/55) while calving rate was 10.91% (6/55) after transfer of in vitro-derived vitrified-warmed embryos to recipient animals. Six healthy and normal calves with average birth weight of 38.75+/-3.55 kg were born from the transferred embryos. These results indicate the viability of vitrified in vitro-derived buffalo embryos and the potential application of in vitro embryo production and vitrification techniques for production and transport of buffalo embryos from germplasm-rich sources to guarantee genetic improvement in many parts of the world.

Developmental failure of hybrid embryos generated by in vitro fertilization of water buffalo (Bubalus bubalis) oocyte with bovine spermatozoa

The developmental potential of inter-species hybrid embryos produced by in vitro fertilization of in vitro matured buffalo oocytes with bovine spermatozoa was studied with a view to investigate pre-implantation embryo development and its gross morphology, early embryonic gene expression, and embryonic genome activation. Fertilization events with both buffalo and cattle spermatozoa were almost similar. Overall fertilization rate with cattle spermatozoa was 78.4% was not significantly different from that of buffalo spermatozoa (80.2%). Initial cleavage rate between buffalo and hybrid embryo was also similar, and there was no significant difference in their developmental rate till 8-cell stage (26.0 +/- 4.1 vs. 24.3 +/- 4.8). However, only 5.3% of hybrid embryos developed into blastocyst stage compared to 21.7% in buffalo. mRNA phenotyping of insulin-like growth factor family (Insulin, insulin receptor, IGF-I, IGF-I receptor, IGF-II, and IGF-II receptor) and glucose transporter isoforms (GLUT-I, II, III, IV) in hybrid embryos clearly showed that these molecules were not expressed after 8-cell stage onward. Similarly, as observed in buffalo embryos, incorporation of (35)S-methionine and (3)H-uridine could not be observed in hybrid embryos from 8-cell stage onward. This suggests that the maternal-zygotic genome activation did not occur in hybrid embryos. Differential staining also showed that the blastomere stopped dividing after 8-cell stage. Collectively, these parameters clearly showed that there was developmental failure of hybrid embryos.

Buffalo and cattle hybrid embryo development is decreased by caffeine treatment during in vitro fertilization

Water buffalo are renowned for difficulties in the implementation of assisted reproductive technologies, with both males and females being problematic. In this study, we used cattle oocytes to assess the effect of treatments with heparin and caffeine on buffalo spermatozoa and subsequent fertilization and embryo development in vitro. There was no significant difference between buffalo and bovine spermatozoa in the events associated with fertilization. Fertilization of cattle oocytes with buffalo spermatozoa resulted in 7.8% of oocytes developing into hybrid embryos. A difference in the developmental capability of hybrid embryos compared with the cattle control was observed. This has not been previously reported. The subsequent transfer of a limited number of hybrid embryos did not produce a viable pregnancy. However, control treatments in this experiment also failed to achieve pregnancy, so objective data is not available to provide conclusions about the developmental competence of the buffalo and cattle hybrid embryos. Optimal spermatozoa capacitation treatments achieved 61% fertilization and 21% zygote cleavage into two cell embryos. There was no significant difference in fertilization or development due to heparin or spermatozoa concentrations. However, treatment of buffalo and cattle spermatozoa with caffeine significantly decreased embryo cleavage but also tended to decrease embryo development to the blastocyst stage. These studies suggest that problems with reproduction in buffalo may reside with biological mechanisms associated with the oocyte that are often complicated by poor male reproductive performance. Selection for bull fertility would prevent some of these complications.

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.

In vitro embryo production in buffalo species: state of the art

In the last several years, there has been an increasing interest in in vitro embryo production (IVEP) technologies for faster propagation of superior germplasm in buffalo because of the low efficiency of superovulation (SO) and embryo transfer (ET) programs in this species. Although the IVEP efficiency has improved, embryo yield and development to term are still very low. This paper reviews the progress made in optimizing the IVM, IVF, and IVC systems. It also highlights the importance of embryo cryopreservation, which might critically contribute to the diffusion of ET procedures in the field. The acquisition of more information on embryo physiology, metabolism, and culture requirements in this species is critical to optimize the efficiency of advanced reproductive strategies. Further studies are also needed to improve the cryopreservation of IVEP embryos. The second part of the work underlines the potential impact of ovum pick-up (OPU) technique combined with IVEP on genetic improvement of buffalos. The OPU technique is a non-invasive and repeatable procedure for recovering large numbers of meiotically competent oocytes from antral follicles of live animals. Our experience, in buffalo, has demonstrated that OPU is superior to SO because it can yield more transferable embryos (TE) per donor on a monthly basis (2 TE vs 0.6, respectively). Therefore this technology has great potential to improve the genetic progress of buffalo through the maternal lineage.

Effect of oviductal cell co-culture on cleavage and development of goat IVF embryos

The present study was undertaken with the aim to study the role of isologous and heterologous (buffalo) oviductal cell to co-culture on in vitro development of goat embryos. The oocytes were collected by puncturing the goat ovaries obtained from slaughterhouse. The oocyte recovery rate per ovary was 3.0. The media used for oocyte maturation and embryo development was TCM-199 + 10 percent buffalo estrus serum. A total of 79.8 percent oocytes got matured out of 1056 oocytes. The oocytes were inseminated with epididymal buck spermatozoa capacitated in Brackett and Oliphant media. In group I without oviductal cells co-culture only 13.6 percent matured oocytes cleaved and 3.3 and 0.0 percent reached the morula and blastocyst stage. In group II and III having goat and buffalo oviductal cells the cleavage was 57.6 and 59.2 percent respectively. The percentage of morula, blastocyst and those embryos arrested between 2-16 cells were 26.3, 10.2, 63.5 and 26.6, 8.9 and 64.5 in goat and buffalo oviductal cell groups. The results indicated that the oviductal cell co-culture had a marked effect on cleavage and development of goat IVF embryos. Buffalo oviductal cells can be used well for goat embryo development.

Effect of insulin-like growth factor I and its interaction with gonadotropins on in vitro maturation and embryonic development, cell proliferation, and biosynthetic activity of cumulus-oocyte complexes and granulosa cells in buffalo

In this study we have examined the effect of insulin like growth factor I (IGF-I) and its interaction with gonadotropins in the presence or absence of granulosa cell coculture on in vitro oocyte maturation (IVM) and their subsequent embryonic development in buffalo. We also have examined the role of IGF-I alone or in combination with gonadotropins on DNA synthesis, steroidogenesis, and protein synthesis of cumulus-oocytes complexes (COCs) and granulosa cells. Results showed that IGF-I stimulates oocytes maturation in a dose-dependent manner, with maximal effect at a dose of 100 ng/ml (P < 0.05). IGF-I showed positive interaction with follicle-stimulating hormone (FSH) in the presence or absence of granulosa cells on meiotic maturation and synergistically enhanced DNA synthesis, protein synthesis, and steroidogenesis in the presence of granulosa cells. This synergistic effect is mainly caused by the increase of IGF-I receptors in granulosa cells by FSH, as evident by [125I]IGF-I binding study. Luteinizing hormone (LH), however, was found to suppress IGF-I and IGF-I + FSH stimulated oocyte maturation. Addition of LH to cultures containing IGF-I + FSH, on the contrary, caused a significant increase in oocyte maturation when cocultured with granulosa cells. Addition of IGF-I during IVM significantly improve cleavage and blastocyst development rate over the control group. However, there was no cumulative effect when IGF-I and gonadotropins were present together. Addition of granulosa cells during IVM, however, enhanced blastocyst development in the IGF-I + FSH and IGF-I + FSH + LH groups. Our results demonstrated that IGF-I is a major follicular factor responsible for stimulating oocyte maturation in the buffalo. Interaction between IGF-I and FSH suggests that they seem to act synergistically as an autocrine and paracrine regulator of granulosa cells and therefore together promote mitosis, steroidogenesis, and protein synthesis.

Inhibition of sperm glutathione S-transferase leads to functional impairment due to membrane damage

The role of glutathione S-transferase (GST) in the defense mechanisms of sperm is not known. We report here interference with normal motility, acrosome reaction and fertilizing ability of the goat sperm as a consequence of inhibition of GST activity. That these functional impairments were due to membrane changes was evident from the alteration in the lipid peroxidation status of these cells after GST inhibitor treatment. Increased reactive oxygen species production by the cell which occurred when GST activity was suppressed may be the mediator for membrane damage. The data argue for a role of GST in maintaining sperm membrane status.

Studies on glutathione S-transferases important for sperm function: evidence of catalytic activity-independent functions

Our earlier studies reported the identification of a rat testicular protein of 24 kDa with significant similarity at the N-terminus with Mu class glutathione S-transferases (GSTs). Treatment of goat sperm with antisera against this protein identified immunoreactive sites on the spermatozoa and inhibited in vitro fertilization of goat oocytes by the antibody-treated sperm. The above observations indicated the presence of GST-like molecule(s) important for fertility related events on goat spermatozoa. In this study, we report the purification of goat sperm GSTs (GSP1) which were purified by glutathione affinity chromatography and were enzymically active towards 1-chloro-2,4,-dinitrobenzene, a general GST substrate, and ethacrynic acid, a substrate for Pi class GSTs. GSP1 resolved into three major components on reverse-phase HPLC: peaks 1 and 2 with molecular masses of 26.5 kDa and peak 3 with a molecular mass of 25.5 kDa, as determined by SDS/PAGE. Multiple attempts to obtain N-terminal sequences of the first two peaks failed, indicating N-terminal block; however, they reacted to specific anti-Mu-GST antisera on Western blots and ELISA, and not to anti-Pi-GST antisera, which provides evidence for the presence of Mu-GST-reactive sites on peaks 1 and 2. The third component showed 80% N-terminal similarity with human and rat GSTP1-1 over an overlap of 15 amino acids, and reacted to anti-Pi-specific antisera in ELISA. Sperm labelled with antibodies against a 10-mer and an 11-mer peptide, designed from the N-terminal sequences of Mu and Pi class GSTs respectively, showed the presence of both Mu- and Pi-GST on goat sperm surface at distinct cellular domains. Selective inhibition of Pi class GST by the Pi-specific antisera, either at 0 h or at 3 h after initiation of sperm capacitation, leads to a reduction in fertilization rates. In contrast, the inhibition of Mu class GST by specific antisera at 0 h does not inhibit fertilization, although such treatment at 3 h after the initiation of capacitation reduces fertilization rates. The results indicate that both Pi- and Mu-GSTs are involved in fertilization, but the Mu-GST sites essential for fertilization are exposed only after 3 h of capacitation. The enzymic activity of GSP1 or live spermatozoa is not inhibited by the two antisera. The inability of the antibodies to cause such inhibition indicates that the reduction in fertilization rates and acrosome reaction caused by the antibodies is through a mechanism which does not interfere with the catalytic activity of the molecule. Therefore we established the presence of Pi and Mu class GST on goat sperm, their localization and their possible function in fertility-related events.

Comparison of various maturation treatments on in vitro maturation of goat oocytes and their early embryonic development and cell numbers

In the present study, comparison of 2 different culture media (Ham's F-12 and M-199) for supporting in vitro maturation of goat oocytes, and their subsequent embryonic development was evaluated in the presence or absence of sera (estrous goat serum, EGS and fetal calf serum, FCS) and hormones (FSH, 0.5 ug/ml, LH, 5 ug/ml and estradiol, 1 ug/ml). Neither medium (Ham's F-12 or M-199) when supplemented with EGS and hormones showed any notable changes in the maturation rate nor in cleavage and blastocyst development. The mean cell number for blastocysts was also significantly low (P < 0.05). However, Ham's F-12 medium supplemented with FCS and hormones showed a considerable increase in the maturation rate, but subsequent embryonic development was not appreciably increased. However, maturation, cleavage and blastocyst development rates of oocytes matured in M-199 medium in combination with 10% FCS and hormones were significantly higher (P < 0.05). Mean cell number per blastocyst was also significantly increased in this latter treatment compared with that of the other groups (P < 0.05). The results thus indicated that both the culture medium and serum have a marked effect on maturation and subsequent embryonic development. Further, the results also showed that the combination of M-199 with FSH, LH and E2 supplemented with 10% FCS was the most efficacious medium for in vitro maturation and subsequent embryonic development of the media, sera and hormone combinations studied.

Differential cleavage and developmental rates and their correlation with cell numbers and sex ratios in buffalo embryos generated in vitro

In vitro matured and fertilized buffalo oocytes were co-cultured with buffalo oviductal epithelial cells (BOEC) in CRlaa medium. Cleaved embryos were separated according to the time of completion of first cleavage (i.e., before 30 h and after 30 h post insemination) and cultured for 5 to 10 d and allowed to develop to the blastocyst stage. Zygotes cleaving before 30 h were termed fast-cleaving while those cleaving after 30 h were termed slow-cleaving. The results indicated that fast-cleaving embryos are more likely to develop into blastocysts (25%) than slow-cleaving embryos (7.8%). The quality and viability of fast-cleaving and fast-developing blastocysts was found to be better than that of slow-cleaving, slow-developing blastocysts as judged by cell numbers (67.7 +/- 3.7 vs 35.2 +/- 2.1). However, the mitotic index was not different between the 2 groups. The sex of fast-developing and slow-developing blastocysts was determined via the polymerase chain reaction (PCR) to correlate the rate of embryonic development with the sex ratio of the embryos. Embryos produced by Bull 293 and Bull M-82, irrespective of their being fast or slow-developing, gave rise to more females and males, respectively. From these results, we suggest that there may be a sire effect on sex ratio of in vitro produced buffalo embryos.