40 years of bovine IVF in the new genomic selection context

Disease risk of in vitro produced embryos: A review of current commercial practices in the context of international trade with emphasis on bovine embryos

The ever-evolving procedures of the practice of in vitro production (IVP) of embryos has well outpaced the ability of governments and institutions to create standardized rules and regulations around the global trade of these reproductive products. There are several challenges related to identifying and quantifying disease transmission risk in IVP embryos, not the least of which is a lack of published information. The International Embryo Technology Society (IETS) Health and Safety Advisory Committee (HASAC) has identified and addressed several of the challenges related to the potential for disease transmission via IVP embryos. This review will outline the current sanitation practices recommended by the IETS for in vivo derived (IVD) embryos, as well as the current practices at most in vitro fertilization (IVF) labs and will present the case that IVP embryos are not only just as safe as IVD embryos from a disease transmission risk standpoint, but perhaps may even be safer than IVD embryos, as the oocyte, zygote, and embryo in the in vitro production system has no contact with the downstream reproductive anatomy (fimbria, isthmus, oviduct, or uterus) of the donor female.

Recipients' and Environmental Factors Affecting the Pregnancy Rates of a Large, Fresh In Vitro Fertilization-Embryo Transfer Program for Dairy Cows in a Commercial Herd in China

The main objective of this study was to determine the influence of the recipient dairy cows' breed, lactation number, estrus condition, the type, location and volume of the corpus luteum (CL) and the time of year that the embryo transfer (ET) was performed on the pregnancy rates of a large, fresh in vitro fertilization-embryo transfer program for dairy cows in a commercial herd in China. The recipients were from a herd of dairy cows in Ningxia, a province in northwest China, and we statistically analyzed the data of 495 cows from 2021 to 2023. Cumulus oocyte complexes (COCS) were isolated from follicular fluid obtained through ovum pick-up (OPU) and oocytes were incubated 20-22 h for in vitro maturation (IVM). Embryos were obtained after 10-12 h of in vitro fertilization (IVF) and six days of in vitro culture (IVC). Embryos at the morula or blastocyst stage were transferred to randomly chosen recipients (n = 495). The influence of recipients' breed (Holstein or other), recipients' lactation number (heifers or cows), estrus type (natural or synchronized), CL type (homogeneous, CLhom or cavitary, CLcav), CL side (left or right), volume of the CL and season of transfer (spring, autumn or winter) on pregnancy rates were determined. The pregnancy rates were analyzed by binomial logistic regression with IBM SPSS statistics software, version 26. Pregnancy rates after ET to Holstein cows and other breeds were 43.49% and 42.68%, respectively (p > 0.05). Regarding age, pregnancy rates were 45.56% for heifers and 30.77% for cows (p < 0.05). Pregnancy rates following ET during natural and synchronized estrus were 44.41% and 41.5%, respectively (p > 0.05). Pregnancy rates with a left- or right-side CL were 40.18% and 45.65%, respectively (p > 0.05). The pregnancy rates achieved with a CLhom and CLcav were 44.44% and 39.68%, respectively (p < 0.05). The rates obtained in spring, autumn and winter were 49.26%, 46.02% and 34.64%, respectively (p < 0.05). Moreover, it was found that pregnancy rates were higher in recipients with a CL volume measuring greater than 10 cm3 compared with those with a CL volume measuring less than 10 cm3 (p < 0.05). The comparisons showed that recipients' breed, estrus type or side of the CL had no effect, but the recipients' lactation number, ET season and the type and volume of the CL have significant effects on pregnancy rates during ET.

TET enzyme driven epigenetic reprogramming in early embryos and its implication on long-term health

Mammalian embryo development is initiated by the union of paternal and maternal gametes. Upon fertilization, their epigenome landscape is transformed through a series of finely orchestrated mechanisms that are crucial for survival and successful embryogenesis. Specifically, maternal or oocyte-specific reprogramming factors modulate germ cell specific epigenetic marks into their embryonic states. Rapid and dynamic changes in epigenetic marks such as DNA methylation and histone modifications are observed during early embryo development. These changes govern the structure of embryonic genome prior to zygotic genome activation. Differential changes in epigenetic marks are observed between paternal and maternal genomes because the structure of the parental genomes allows interaction with specific oocyte reprogramming factors. For instance, the paternal genome is targeted by the TET family of enzymes which oxidize the 5-methylcytosine (5mC) epigenetic mark into 5-hydroxymethylcytosine (5hmC) to lower the level of DNA methylation. The maternal genome is mainly protected from TET3-mediated oxidation by the maternal factor, STELLA. The TET3-mediated DNA demethylation occurs at the global level and is clearly observed in many mammalian species. Other epigenetic modulating enzymes, such as DNA methyltransferases, provide fine tuning of the DNA methylation level by initiating de novo methylation. The mechanisms which initiate the epigenetic reprogramming of gametes are critical for proper activation of embryonic genome and subsequent establishment of pluripotency and normal development. Clinical cases or diseases linked to mutations in reprogramming modulators exist, emphasizing the need to understand mechanistic actions of these modulators. In addition, embryos generated via in vitro embryo production system often present epigenetic abnormalities. Understanding mechanistic actions of the epigenetic modulators will potentially improve the well-being of individuals suffering from these epigenetic disorders and correct epigenetic abnormalities in embryos produced in vitro. This review will summarize the current understanding of epigenetic reprogramming by TET enzymes during early embryogenesis and highlight its clinical relevance and potential implication for assisted reproductive technologies.

In Vitro Culture of Mammalian Embryos: Is There Room for Improvement?

Preimplantation embryo culture, pivotal in assisted reproductive technology (ART), has lagged in innovation compared to embryo selection advancements. This review examines the persisting gap between in vivo and in vitro embryo development, emphasizing the need for improved culture conditions. While in humans this gap is hardly estimated, animal models, particularly bovines, reveal clear disparities in developmental competence, cryotolerance, pregnancy and live birth rates between in vitro-produced (IVP) and in vivo-derived (IVD) embryos. Molecular analyses unveil distinct differences in morphology, metabolism, and genomic stability, underscoring the need for refining culture conditions for better ART outcomes. To this end, a deeper comprehension of oviduct physiology and embryo transport is crucial for grasping embryo-maternal interactions' mechanisms. Research on autocrine and paracrine factors, and extracellular vesicles in embryo-maternal tract interactions, elucidates vital communication networks for successful implantation and pregnancy. In vitro, confinement, and embryo density are key factors to boost embryo development. Advanced dynamic culture systems mimicking fluid mechanical stimulation in the oviduct, through vibration, tilting, and microfluidic methods, and the use of innovative softer substrates, hold promise for optimizing in vitro embryo development.

Use of assisted reproductive technologies (ARTs) to shorten the generational interval in ruminants: current status and perspectives

The challenges posed by climate change and increasing world population are stimulating renewed efforts for improving the sustainability of animal production. To meet such challenges, the contribution of genomic selection approaches, in combination with assisted reproductive technologies (ARTs), to spreading and preserving animal genetics is essential. The largest increase in genetic gain can be achieved by shortening the generation interval. This review provides an overview of the current status and progress of advanced ARTs that could be applied to reduce the generation time in both female and male of domestic ruminants. In females, the use of juvenile in vitro embryo transfer (JIVET) enables to generate offspring after the transfer of in vitro produced embryos derived from oocytes of prepubertal genetically superior donors reducing the generational interval and acceleration genetic gain. The current challenge is increasing in vitro embryo production (IVEP) from prepubertal derived oocytes which is still low and variable. The two main factors limiting IVEP success are the intrinsic quality of prepubertal oocytes and the culture systems for in vitro maturation (IVM). In males, advancements in ARTs are providing new strategies to in vitro propagate spermatogonia and differentiate them into mature sperm or even to recapitulate the whole process of spermatogenesis from embryonic stem cells. Moreover, the successful use of immature cells, such as round spermatids, for intracytoplasmic injection (ROSI) and IVEP could allow to complete the entire process in few months. However, these approaches have been successfully applied to human and mouse whereas only a few studies have been published in ruminants and results are still controversial. This is also dependent on the efficiency of ROSI that is limited by the current isolation and selection protocols of round spermatids. In conclusion, the current efforts for improving these reproductive methodologies could lead toward a significant reduction of the generational interval in livestock animals that could have a considerable impact on agriculture sustainability.

Evaluation of blastocyst re-expansion, quality in relation to storage temperature, and sexing using blastocoel fluid after manual perforation with a hand-held needle involving in vivo produced equine embryos

The present study was designed to evaluate equine blastocyst re-expansion rate, quality, and sex following perforation of the blastocoel, collection of blastocoel fluid (BF), and PCR amplification of free DNA. Experiment 1 tested the feasibility of the BF sample collection with a hand-held, small-gauged needle (26g) and subsequent PCR amplification of the TSP-Y gene for males and AMEL-Y gene for males and AMEL-X gene for females. Experiment 2 tested the application of the technique. Equine embryos were collected via uterine flushes 8d after ovulation. Thereafter, embryos (n = 19) were initially assessed and transferred to a 50 μL droplet of holding medium in which the blastocoel was manually perforated as in Experiment 1. Within 1 min of detecting a diameter decrease or collapse, the entire volume of each droplet of medium was collected and stored at -20 °C until PCR. In Experiment 1, amplification of the TSP-Y gene was positive for males at 60% (9/15) and negative for females at 40% (6/15). In Experiment 2, a total of 42 embryos were randomly assigned to a collapsed embryo (CE) or intact embryo (IE) groups and stored at room temperature (RT, 25 °C) or cold temperature (CT, 5 °C) for 24h as follows: 1) CERT, n = 11; 2) CECT n = 11; 3) IERT, n = 10; and 4) IECT, n = 10. After 24h, embryo diameter and quality were reassessed. For all collapsed embryos (n = 19), blastocoel fluid was subjected to double PCR amplification of the TSPY gene with blood from adult male and female horses as controls. Positive gene amplification indicated 57.9% (11/19) of embryos were male and negative amplification indicated 31.6% (6/19) of embryos were female. Relative to the least diameter (0%) after perforation of collapsed embryos or fullest diameter (100%) of intact embryos at T0, percentage change in diameter and quality Grade 1 or 2 embryos after 24h of storage for all groups were, respectively: 31.2% and 54% for CERT group, 28.2% and 0% for CECT group, 25.9% and 100% for IERT group, 4.3% and 80% for IECT group, respectively. Thus, needle-induced leakage and collapse of the blastocoel at T0 resulted in a high rate of blastocyst re-expansion (69%) with many embryos (54%) achieving good quality at T24 with potential for transfer as either male or female embryos. For both collapsed and intact embryos, it was observed that storage for 24h at room temperature (25 °C) was associated with improved embryo growth and morphological quality compared to storage at cold temperature (5 °C).

How great thou ART: biomechanical properties of oocytes and embryos as indicators of quality in assisted reproductive technologies

Assisted Reproductive Technologies (ART) have revolutionized infertility treatment and animal breeding, but their success largely depends on selecting high-quality oocytes for fertilization and embryos for transfer. During preimplantation development, embryos undergo complex morphogenetic processes, such as compaction and cavitation, driven by cellular forces dependent on cytoskeletal dynamics and cell-cell interactions. These processes are pivotal in dictating an embryo's capacity to implant and progress to full-term development. Hence, a comprehensive grasp of the biomechanical attributes characterizing healthy oocytes and embryos is essential for selecting those with higher developmental potential. Various noninvasive techniques have emerged as valuable tools for assessing biomechanical properties without disturbing the oocyte or embryo physiological state, including morphokinetics, analysis of cytoplasmic movement velocity, or quantification of cortical tension and elasticity using microaspiration. By shedding light on the cytoskeletal processes involved in chromosome segregation, cytokinesis, cellular trafficking, and cell adhesion, underlying oogenesis, and embryonic development, this review explores the significance of embryo biomechanics in ART and its potential implications for improving clinical IVF outcomes, offering valuable insights and research directions to enhance oocyte and embryo selection procedures.

Effect of follicular wave synchronization using a progesterone-releasing intravaginal device-based protocol on in vitro embryo production in Bos taurus cows subjected to 14-day intervals ovum pick-up

Follicular wave synchronization (FWS) before ovum pick-up (OPU) is one of the strategies used to improve the efficiency of in vitro embryo production (IVP). This study aimed to evaluate the effect of FWS on the total follicular number, cumulus-oocyte complex (COC) recovery, and in vitro embryo development in Angus cows (n = 33) subjected to OPU with 14-day intersession intervals. Additionally, it was also evaluated the presence of carryover effects given the short intersession interval used. The experiment was run as a 2-treatment (FWS vs. Control) x 2-period (1 vs. 2) crossover design. Animals in the FWS group received an intravaginal progesterone implant (1gr), estradiol benzoate (2 mg), and D-cloprostenol (150 μg) on day 0 and the OPU was performed on day 5. Control group animals did not receive any hormone treatment. The FWS increased the number of 6-10 mm follicles (P = 0.05), but it decreased the COC recovery rate (P < 0.01). The FWS did not affect the total or frozen embryo numbers (P = 0.49 and P = 0.17; respectively), but it increased the total blastocyst cell number (P < 0.01). A carryover effect was found on the total and < 6 mm follicles number (P = 0.10 and P < 0.01; respectively), and on the regular, atretic, viable, and total number of COC (P = 0.01, P = 0.08, P = 0.02 and P < 0.01; respectively). We concluded that the FWS increased the quality of embryos after OPU with 14-day intersession intervals in Angus cows and that this kind of OPU/IVP scheme enabled the existence of a carryover effect, especially on the follicle number and COC morphology.

Experiences with transvaginal Ovum Pick-Up (OPU) in sows

Transvaginal ultrasound-guided Ovum Pick-Up (OPU) is an established technique in other species. Due to several challenges, there are few publications addressing the procedure in sows. An efficient OPU technique may allow for the collection of numerous oocytes from valuable sows for porcine in vitro embryo production, gene editing and cloning programmes, or cryopreservation. We aimed to improve transvaginal OPU and equipment for this technique in sows. In experiment 1, we conducted 13 OPU sessions on three Landrace x Large White hybrid sows under general anaesthesia, while the second experiment explored OPU in non-sedated animals (N = 6) physically restrained in a commercial claw trimming chute. The experiments resulted in 6.6 ± 5.6 (mean ± SD) and 7.7 ± 8.9 recovered cumulus-oocyte complexes per session, respectively. Post-mortem examination of the pelvic and abdominal cavities of the three sows subjected to repeated OPU sessions did not reveal major acute or chronic pathological lesions. The only sow which was inseminated after the experiment delivered 16 liveborn piglets at term. Salivary cortisol levels increased during the procedure in non-sedated and physically restrained sows but returned to baseline 1 h later (n = 5), indicating a short-term stress response. The described OPU technique and equipment have the potential to retrieve considerable numbers of oocytes by repeated procedures on valuable mature sows. Follow-up studies are needed to optimize the efficiency of the aspiration of high-quality oocytes and to describe the developmental competence of these OPU-derived oocytes. It is also essential to further investigate sow welfare during and after the procedure before recommending porcine transvaginal OPU as a sustainable and welfare-friendly procedure.

Improving Cryopreservation Efficiency and Pregnancy Rate through Superovulation with Follicle-Stimulating Hormone in Korean Hanwoo Cows via Ovum Pick Up

The aim of this study was to devise an efficient technique for generating embryos from high-quality bovine females. Oocytes were collected from 20 control and 15 Hanwoo (Bos taurus coreanae) females treated with the FSH. A combination of decreasing FSH doses (36, 36, 24, and 24 mg, 12 h apart), progesterone, estrogen, and prostaglandins were administered to synchronize and mildly stimulate the animals. The FSH-treated group (1125 oocytes) and control group (1022 oocytes) exhibited a higher proportion of grade A and B oocytes (88.2%) than the other grades (p < 0.05), with most at the germinal vesicle 2 stage (64.0%). Moreover, the FSH-treated group achieved a notably higher blastocyst rate (44.7%) compared to the control group (31.1%) (p < 0.05). After undergoing vitrification and in vitro culture (IVC) warming, embryos in the FSH group exhibited higher re-expansion rates (grade 1: 86.9%; grades 2 and 3: 57.9%) compared to those in the control (p < 0.05). This highlights the positive impact of FSH treatment on in vitro embryo production (IVEP) and the OPU rate.

Review: Environment of the ovulatory follicle: modifications and use of biotechnologies to enhance oocyte competence and increase fertility in cattle

The oocyte is the basis of life, supporting development from a fertilized cell to an independent multicellular organism. The oocyte's competence to drive the first cell cycles postfertilization are critical to embryonic survival and subsequent successful pregnancy. Coupled with the complex processes of follicle assembly, activation, differentiation, growth, and terminal maturation, oocyte developmental competence is gradually acquired during oocyte growth and meiotic maturation. Most reproduction management technologies and interventions are centered around these highly coordinated processes, targeting the ovarian follicle and the oocyte within. Thus, our objective was to highlight key aspects of oocyte and follicle development in cattle, and to discuss recent advances in oocyte and follicle-centered reproductive biotechnologies.

Review: Use of assisted reproduction in seasonal-calving dairy herds

A unique aspect of seasonal-calving pasture-based systems of dairy production is the intense focus placed on achieving a concentrated herd-calving period in late winter and early spring. Hence, excellent reproductive performance is required during a short breeding period. A concentrated calving period also produces a problem in the form of a large number of male dairy calves being born at the same time; as these calves have little economic value due to poor beef merit, they present a potential welfare concern. A solution exists in the form of sex-sorted semen, but this is typically associated with poorer pregnancy per artificial insemination, and hence, the use of sex-sorted semen must be carefully considered. The logical strategy to use sex-sorted semen is to target the best genetic merit dams in the herd to generate replacement heifers, thereby accelerating herd genetic gain. On the other hand, if all dairy farmers adopt such a strategy, there will be a corresponding reduction in elite genetic merit male dairy calves being born, potentially reducing availability of the next generation of future bulls to be used for artificial insemination. Use of in vitro embryo production on elite dairy donors could avoid this problem by acting as a multiplier, potentially in tandem with Y-sorted semen to skew the offspring sex ratio towards more male calves. Use of sex-sorted semen on the best genetic merit dams can also facilitate a marked increase in the usage of beef semen on any dams that are deemed unsuitable for sex-sorted semen. The use of "beef on dairy" requires selection of beef bulls that generate offspring with traits that meet the key requirements of both the dairy farmer (e.g., gestation length and calving ease) and the beef farmer that must be motivated to purchase the calves (e.g., growth rate, age at slaughter, carcass value). Beef breed dams that have elite genetic merit for these traits could also be considered for in vitro embryo production, potentially in tandem with Y-sorted semen, to facilitate genetic gain for the growing "beef-on-dairy" market. It is possible to transfer a beef embryo (75-100% beef breed genetics) into dairy dams that are not required to generate replacements, but this is likely to remain a niche practice as there are many barriers to widespread adoption. Such combinations of assisted reproduction have the potential to improve the efficiency and sustainability metrics of seasonal-calving pasture-based dairy herds.

Development of a Microfluidic Chip Powered by EWOD for In Vitro Manipulation of Bovine Embryos

Digital microfluidics (DMF) holds great potential for the alleviation of laboratory procedures in assisted reproductive technologies (ARTs). The electrowetting on dielectric (EWOD) technology provides dynamic culture conditions in vitro that may better mimic the natural embryo microenvironment. Thus far, EWOD microdevices have been proposed for in vitro gamete and embryo handling in mice and for analyzing the human embryo secretome. This article presents the development of the first microfluidic chip utilizing EWOD technology designed for the manipulation of bovine embryos in vitro. The prototype sustains the cell cycles of embryos manipulated individually on the chips during in vitro culture (IVC). Challenges related to the chip fabrication as well as to its application during bovine embryo IVC in accordance with the adapted on-chip protocol are thoroughly discussed, and future directions for DMF in ARTs are indicated.

Preimplantation Developmental Competence of Bovine and Porcine Oocytes Activated by Zinc Chelation

After sperm-oocyte fusion, intracytoplasmic rises of calcium (Ca) induce the release of zinc (Zn) out of the oocyte (Zn sparks). Both phenomena are known to play an essential role in the oocyte activation process. Our work aimed to explore different protocols for activating bovine and porcine oocytes using the novel zinc chelator 1,10-phenanthroline (PHEN) and to compare developmental rates and quality to bovine IVF and parthenogenetic ionomycin-induced embryos in both species. Different incubation conditions for the zinc chelator were tested, including its combination with ionomycin. Embryo quality was assessed by immunofluorescence of SOX2, SOX17, OCT4, and CDX2 and total cell number at the blastocyst stage. Even though blastocyst development was achieved using a zinc chelator in bovine, bypassing calcium oscillations, developmental rates, and blastocyst quality were compromised compared to embryos generated with sperm-induced or ionomycin calcium rise. On the contrary, zinc chelation is sufficient to trigger oocyte activation in porcine. Additionally, we determined the optimal exposure to PHEN for this species. Zinc chelation and artificial induction of calcium rise combined did not improve developmental competence. Our results contribute to understanding the role of zinc during oocyte activation and preimplantation embryo development across different mammalian species.

Simple and Efficient Chemically Defined In Vitro Maturation and Embryo Culture System for Bovine Embryos

Supplementation of the culture media for in vitro production (IVP) of bovine embryos with fetal bovine serum (FBS) is associated with inconsistent outcomes. The present study sought to replace FBS and BSA by insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF). In Experiment 1, absence of FBS from maturation medium (MM) did not affect the rate of in vitro maturation, as assessed by the extrusion of the first polar body. However, when gonadotropins and FBS were removed from the MM, the maturation rate was significantly reduced even in the presence of growth factors. Therefore, gonadotropin-supplemented MM medium was established as the base medium for the defined maturation condition. In Experiment 2, the addition of growth factors to gonadotropin-supplemented MM medium supported similar maturation (~90%) compared to the undefined condition (FBS-carrying). In Experiment 3, the addition of growth factors to embryo culture medium showed similar in vitro competence compared to the undefined (FBS) control. In Experiment 4, completely defined conditions (absence of FBS and BSA during in vitro maturation and embryo culture) were tested. A higher cleavage was observed with FGF2 (86%) compared to EGF (77%) and the FBS control (77%), but similar blastocyst rates were observed for FGF2 (24%), EGF (19%) and the FBS control (25%). Embryo quality was similar among groups. Finally, post-thawing survival was higher for FGF2 (94%) compared to the FBS control (77%). Thus, we report a simple defined IVP system for bovine species that generates developmental outcomes and embryos of similar quality than those produced under conditions containing FBS.

Extracellular vesicles from seminal plasma improved development of in vitro-fertilized mouse embryos

In vitro fertilization (IVF) has wide application in human infertility and animal breeding. It is also used for research on reproduction, fertility and development. However, IVF embryos are still inferior to their in vivo counterparts. Some substances in seminal plasma appear to have important roles in embryo development, and during the traditional IVF procedure, the seminal plasma is washed away. In this study, extracellular vesicles (EVs) were concentrated from seminal plasma by ultracentrifugation, visualized using transmission electron microscopy, and particle size distributions and concentrations were determined with a NanoSight particle analyzer. We found particles of various sizes in the seminal plasma, the majority having diameters ranging from 100 to 200 nm and concentrations of 6.07 × 10¹⁰ ± 2.91 × 10⁹ particles/ml. Addition of seminal plasma EVs (SP-EVs) to the IVF medium with mouse oocytes and sperm significantly increased the rate of blastocyst formation and the inner cell mass (ICM)/trophectoderm (TE) cell ratio, and reduced the apoptosis of blastocysts. Our findings provide new insights into the role of seminal plasma EVs in mediating embryo development and it suggests that SP-EVs may be used to improve the developmental competence of IVF embryos, which has important significance for assisted reproduction in animals and humans.

Black Elder and Its Constituents: Molecular Mechanisms of Action Associated with Female Reproduction

The present review summarizes the current knowledge concerning provenance, properties, physiological and therapeutic actions of elderberry and the bioactive molecules present in the plant, with emphasis on their action on female reproduction. Elderberry or black elder (Sambucus nigra L.) attracts attention due to its easy cultivation and high availability of bioactive compounds. Most of the available data concerning black elder’s therapeutic action are focused on its effects such as activation of immune processes and anti-inflammatory processes (cytokine production, etc.) and regulation of hormones and their receptors in cancer cells. The effects of elderberry on reproduction have been poorly investigated so far. Nevertheless, conducted studies so far demonstrate the stimulatory influence of black elder extract and its constituents, such as rutin, anthocyanins and agglutinins, on the viability and steroidogenesis of healthy ovarian cells as well as their ability to promote apoptosis and reduce the viability and proliferation of ovarian cancer cells. Furthermore, the action of black elder extract and its constituent biomolecules, such as anthocyanins and lectins, on embryogenesis and the embryonal estradiol-estradiol receptor system have also been reported. The available information, despite limitations, suggest the applicability of black elder constituents for improvement of reproductive processes in animal biotechnology, animal production and assisted reproduction, as well as for prevention and treatment of reproductive disorders (including cancer) in veterinary and human medicine.

Year-Long Phenotypical Study of Calves Derived From Different Assisted-Reproduction Technologies

Assisted reproductive technologies play a major role in the cattle industry. An increase in the use of in vitro-derived embryos is currently being seen around the globe. But the efficiency and quality of the in vitro-derived embryos are substandard when compared to the in vivo production. Different protocols have been designed to overcome this issue, one of those being the use of reproductive fluids as supplementation to embryo culture media. In this study, in vitro-derived calves produced with reproductive fluids added to their embryo production protocol were followed for the first year of life pairwise with their in vivo control, produced by artificial insemination (AI), and their in vitro control, produced with standard supplementation in embryo production. The objective was to assess if any differences could be found in terms of growth and development as well as hematological and biochemical analytes between the different systems. All the analysed variables (physical, hematological, and biochemical) were within physiological range and very similar between calves throughout the entire experiment. However, differences were more evident between calves derived from standard in vitro production and AI. We concluded that the use of reproductive fluids as a supplementation to the embryo culture media results in calves with closer growth and development patterns to those born by AI than the use of bovine serum albumin as supplementation.

Intrauterine administration of peripheral blood mononuclear cells (PBMCs) improves embryo implantation in mice by regulating local Treg/Th17 cell balance

Immune imbalance of Treg/Th17 cells may contribute to recurrent implantation failure (RIF) during in vitro fertilization and embryo transfer (IVF-ET). In this study, we sought to determine the effect of intrauterine administration of mouse PBMCs prior to embryo implantation on endometrial receptivity and embryo implantation, and examine the underlying mechanism of Treg/Th17 cell balance following intrauterine administration of PBMCs. Pregnant mice were randomly divided into three groups: control group, embryo implantation dysfunction (EID) group, and EID with PBMCs group, and the number of embryo implantation sites was recorded during early pregnancy (Pd7.5). The balance of Treg/Th17 cells in the peripheral blood, spleen, and local implantation sites was detected during the peri-implantation period (Pd4.0) and early pregnancy (Pd7.5). The EID group demonstrated a significant decrease in the number of embryo implantation sites, while the EID with PBMCs group demonstrated higher number of embryo implantation sites compared to the EID group. The balance of Treg/Th17 cells in the peripheral blood and spleen tissues was not significantly different between the aforementioned groups. However, the local uterine ratio of the Treg/Th17 cells increased in the EID with PBMCs group compared to that in the EID group. Collectively, we found that intrauterine administration of PBMCs prior to embryo implantation effectively promotes embryo implantation rates. This may be attributed to the improvement in the local immune balance of Treg and Th17 cells compared with the overall immune balance.

Use of Agriculturally Important Animals as Models in Biomedical Research

Livestock have contributed significantly to advances in biomedicine and offer unique advantages over rodent models. The human is the ideal biomedical model; however, ethical reasons limit the testing of hypotheses and treatments in humans. Rodent models are frequently used as alternatives to humans due to size, low cost, and ease of genetic manipulation, and have contributed tremendously to our understanding of human health and disease. However, the use of rodents in translational research pose challenges for researchers due to physiological differences to humans. The use of livestock species as biomedical models can address these challenges as livestock have several similarities to human anatomy, physiology, genetics, and metabolism and their larger size permits collection of more frequent and often larger samples. Additionally, recent advances in genetics in livestock species allow for studies in genomics, proteomics, and metabolomics, which have the added benefit of applications to both humans in biomedical research and livestock in improving production. In this review, we provide an overview of scientific findings using livestock and benefits of each model to the livestock industry and to biomedical research.

Invited review: Use of assisted reproduction techniques to accelerate genetic gain and increase value of beef production in dairy herds

The contribution of the calf enterprise to the profit of the dairy farm is generally considered small, with beef bull selection on dairy farms often not considered a high priority. However, this is likely to change in the future as the rapid rate of expansion of the dairy herd in some countries is set to plateau and improvements in dairy herd fertility combine to reduce the proportion of dairy breed calves required on dairy farms. This presents the opportunity to increase the proportion of beef breed calves born, increasing both the value of calf sales and the marketability of the calves. Beef embryos could become a new breeding tool for dairies as producers need to reassess their breeding policy as a consequence of welfare concerns and poor calf prices. Assisted reproductive technologies can contribute to accelerated genetic gain by allowing an increased number of offspring to be produced from genetically elite dams. There are the following 3 general classes of donor females of interest to an integrated dairy-beef system: (1) elite dairy dams, from which oocytes are recovered from live females using ovum pick-up and fertilized in vitro with semen from elite dairy bulls; (2) elite beef dams, where the oocytes are recovered from live females using ovum pick-up and fertilized with semen from elite beef bulls; and (3) commercial beef dams (≥50% beef genetics), where ovaries are collected from the abattoir postslaughter, and oocytes are fertilized with semen from elite beef bulls that are suitable for use on dairy cows (resulting embryo with ≥75% beef genetics). The expected benefits of these collective developments include accelerated genetic gain for milk and beef production in addition to transformation of the dairy herd calf crop to a combination of good genetic merit dairy female calves and premium-quality beef calves. The aim of this review is to describe how these technologies can be harnessed to intensively select for genetic improvement in both dairy breed and beef breed bulls suitable for use in the dairy herd.

Epigenomic and transcriptomic analyses reveal early activation of the HPG axis in in vitro-produced male dairy calves

In cattle, several calves born after IVP ("in vitro" embryo production) present similar birthweight to those generated after MOET (multiple ovulation and embryo transfer). However, the underlying molecular patterns in organs involved in the developmental process are unknown and could indicate physiological programming. The objectives of this study were: (1) to compare epigenomic and transcriptomic modifications in the hypothalamus, pituitary, gonadal and adrenal organs between 3 months old ovum pick-up-IVP and MOET male calves (n = 4 per group) and (2) to use blood epigenomic data to proxy methylation of the inner organs. Extracted gDNA and RNA were sequenced through whole-genome bisulfite sequencing and RNA sequencing, respectively. Next, bioinformatic analyses determined differentially methylated cytosines (DMC) and differentially expressed genes (DEG) (FDR < 0.05) in IVP versus MOET samples and the KEGG pathways that were overrepresented by genes associated with DMC or DEG (FDR < 0.1). Pathways related to hypothalamus, pituitary, gonadal (HPG) axis activation (GnRH secretion in the hypothalamus, GnRH signaling in the pituitary, and steroidogenesis in the testicle) were enriched in IVP calves. Modeling the effect of the methylation levels and the group on the expression of all the genes involved in these pathways confirmed their upregulation in HPG organs in IVP calves. The application of the DIABLO method allowed the identification of 15 epigenetic and five transcriptomic biomarkers, which were able to predict the embryo origin using the epigenomic data from the blood. In conclusion, the use of an integrated epigenomic-transcriptomic approach suggested an early activation of the HPG axis in male IVP calves compared to MOET counterparts, and the identification of potential biomarkers allowed the use of blood samples to proxy methylation levels of the relevant internal organs.

Effect of exogenous glutathione supplementation on the in vitro developmental competence of ovine oocytes

The beneficial effect of glutathione (GSH) on the in vitro maturation (IVM) of bovine/porcine oocytes has been confirmed; however, the antioxidant effect of exogenous GSH supplementation on the IVM of ovine oocytes has not been determined. In this study, ovine cumulus oocyte complexes (COCs) were classified into three groups according to the layer number of cumulus cells (the Grade A group has more than five layers, the Grade B group has three to four layers and the Grade C group has less than three layers). After in vitro culture of COCs in the presence of exogenous GSH, the meiotic competence of ovine oocytes was assessed by analyzing nuclear maturation to metaphase II (MII) stage, cortical granules (CGs) dynamics, astacin like metalloendopeptidase (ASTL) distribution, histone methylation pattern, reactive oxygen species (ROS) production, mitochondrial activities and genes expression. After in vitro fertilization (IVF), assessments of embryonic development were conducted to confirm the effects of exogenous GSH supplementation. The results showed that exogenous GSH not only enhanced the maturation rates of the Grade B and Grade C groups but also promoted CGs dynamics and ASTL distribution of the Grade A, B and C groups (p < 0.05). Exogenous GSH increased the mitochondrial activities of the Grade A, B and C groups and decreased the ROS production levels of oocytes (p < 0.05), regardless of the layer number of cumulus cells. Moreover, exogenous GSH promoted the expression levels of genes related with oocyte maturation, antioxidant activity and antiapoptotic effects in the Grade B and Grade C groups (p < 0.05). The expression levels of H3K4me3 and H3K9me3 in the Grade B and Grade C groups were promoted after exogenous GSH supplementation (p < 0.05), consistent with the expression levels of genes related with histone methylation (p < 0.05). In addition, exogenous GSH strongly promoted the embryonic developmental competence of Grade B and Grade C groups (p < 0.05). Taken together, our findings provide foundational evidence for the free radical scavenging potential of exogenous GSH in the in vitro developmental competence of ovine oocytes, especially oocytes from COCs lacking cumulus cells. These findings, which demonstrated the potential for improving the quality of ovine oocytes during IVM, will contribute to researches on GSH applications and the efficiency of assisted reproductive technology for ovine breeding.

Tauroursodeoxycholic acid/TGR5 signaling promotes survival and early development of glucose-stressed porcine embryos†

Conditions of impaired energy and nutrient homeostasis, such as diabetes and obesity, are associated with infertility. Hyperglycemia increases endoplasmic reticulum stress as well as oxidative stress and reduces embryo development and quality. Oxidative stress also causes deoxyribonucleic acid damage, which impairs embryo quality and development. The natural bile acid tauroursodeoxycholic acid reduces endoplasmic reticulum stress and rescues developmentally incompetent late-cleaving embryos, as well as embryos subjected to nuclear stress, suggesting the endoplasmic reticulum stress response, or unfolded protein response, and the genome damage response are linked. Tauroursodeoxycholic acid acts via the Takeda-G-protein-receptor-5 to alleviate nuclear stress in embryos. To evaluate the role of tauroursodeoxycholic acid/Takeda-G-protein-receptor-5 signaling in embryo unfolded protein response, we used a model of glucose-induced endoplasmic reticulum stress. Embryo development was impaired by direct injection of tauroursodeoxycholic acid into parthenogenetically activated oocytes, whereas it was improved when tauroursodeoxycholic acid was added to the culture medium. Attenuation of the Takeda-G-protein-receptor-5 precluded the positive effect of tauroursodeoxycholic acid supplementation on development of parthenogenetically activated and fertilized embryos cultured under standard conditions and parthenogenetically activated embryos cultured with excess glucose. Moreover, attenuation of tauroursodeoxycholic acid/Takeda-G-protein-receptor-5 signaling induced endoplasmic reticulum stress, oxidative stress and cell survival genes, but decreased expression of pluripotency genes in parthenogenetically activated embryos cultured under excess glucose conditions. These data suggest that Takeda-G-protein-receptor-5 signaling pathways link the unfolded protein response and genome damage response. Furthermore, this study identifies Takeda-G-protein-receptor-5 signaling as a potential target for mitigating fertility issues caused by nutrient excess-associated blastomere stress and embryo death.

Local action of cytokines and immune cells in communication between the conceptus and uterus during the critical period of early embryo development, attachment and implantation - Implications for embryo survival in cattle: A review

Early embryo development, implantation and pregnancy involve a complex dialogue between the embryo and mother. In cattle this dialogue starts as early as days 3-4 when the embryo is still in the oviduct, and it continues to implantation. Immunological processes involving cytokines, mast cells and macrophages form an important part of this dialogue. Amongst the cytokines, interleukin-6 (Il-6) and leukemia inhibitory factor (LIF) are secreted by both the embryo and uterine endometrium and form part of an ongoing and reciprocating dialogue. Mast cells and macrophages populate the uterine endometrium during embryo development and are involved in achieving the correct balance between inflammatory and anti-inflammatory reactions at the uterus that are associated with embryo attachment and implantation. Embryo loss is the major cause of reproductive wastage in cattle, and livestock generally. A deeper understanding of immunological processes during early embryo development will help to achieve the next step change in the efficiency of natural and assisted breeding.

Genomic Analysis, Progress and Future Perspectives in Dairy Cattle Selection: A Review

Genomics comprises a set of current and valuable technologies implemented as selection tools in dairy cattle commercial breeding programs. The intensive progeny testing for production and reproductive traits based on genomic breeding values (GEBVs) has been crucial to increasing dairy cattle productivity. The knowledge of key genes and haplotypes, including their regulation mechanisms, as markers for productivity traits, may improve the strategies on the present and future for dairy cattle selection. Genome-wide association studies (GWAS) such as quantitative trait loci (QTL), single nucleotide polymorphisms (SNPs), or single-step genomic best linear unbiased prediction (ssGBLUP) methods have already been included in global dairy programs for the estimation of marker-assisted selection-derived effects. The increase in genetic progress based on genomic predicting accuracy has also contributed to the understanding of genetic effects in dairy cattle offspring. However, the crossing within inbred-lines critically increased homozygosis with accumulated negative effects of inbreeding like a decline in reproductive performance. Thus, inaccurate-biased estimations based on empirical-conventional models of dairy production systems face an increased risk of providing suboptimal results derived from errors in the selection of candidates of high genetic merit-based just on low-heritability phenotypic traits. This extends the generation intervals and increases costs due to the significant reduction of genetic gains. The remarkable progress of genomic prediction increases the accurate selection of superior candidates. The scope of the present review is to summarize and discuss the advances and challenges of genomic tools for dairy cattle selection for optimizing breeding programs and controlling negative inbreeding depression effects on productivity and consequently, achieving economic-effective advances in food production efficiency. Particular attention is given to the potential genomic selection-derived results to facilitate precision management on modern dairy farms, including an overview of novel genome editing methodologies as perspectives toward the future.

Benefits and Risks of Preventing Twin Pregnancies

Clinical problems associated with twin pregnancies have been well established, and twin births are now considered undesirable or even disastrous for the dairy cattle industry and the individual cow. The high incidence of early fetal loss, abortion during the mid-lactation period, dystocia, stillbirth, and placenta retention should be considered a preventable consequence of management, as these disorders greatly compromise the welfare and productive lifespan of a cow carrying or delivering twins. The use of sexed semen generates herd replacements and additional heifers, so a proposed strategy for twin pregnancy prevention is the transfer of a single in vitro-produced female beef cow embryo to cows not suitable for producing replacements. Another proposed strategy is drainage at insemination of co-dominant follicles to prevent twin pregnancies in cows with genetic merit. As a result, embryo survival should improve, economic losses associated with twin pregnancies will be prevented, beef output from the herd will be increased, and the health and welfare of the cow will certainly benefit. In this review, the clinical prospects of preventing or avoiding twin pregnancies using both procedures are discussed.

Cellular Fragments in the Perivitelline Space Are Not a Predictor of Expanded Blastocyst Quality

The presence of cellular fragments in the perivitelline space is a commonly used parameter to determine quality before transfer of in vitro produced (IVP) embryos. However, this parameter is difficult to assess after blastocyst expansion. In this study, we used mechanical hatching to confirm the presence of cellular fragments in the perivitelline space of bovine IVP blastocysts. We further looked for associations between possible apoptosis within extruded cells/ cellular fragments and the quality of bovine blastocysts using quantitative RT-PCR and immunofluorescence. Surprisingly, more than 42% of expanded blastocysts had cellular fragments in the perivitelline space; however, more than 37% of extruded cells were TUNEL negative. We observed no significant difference in embryo quality between expanded blastocysts with and without cellular fragments in the perivitelline space. Overall, our data suggest that embryos extrude abnormal cells to maintain their developmental potential. The presence of fragmented cells is not an indicator of embryo quality.

Senescence and Apoptosis During in vitro Embryo Development in a Bovine Model

According to the World Health Organization, infertility affects up to 14% of couples under reproductive age, leading to an exponential rise in the use of assisted reproduction as a route for conceiving a baby. In the same way, thousands of embryos are produced in cattle and other farm animals annually, leading to increased numbers of individuals born. All reproductive manipulations entail deviations of natural phenotypes and genotypes, with in vitro embryo technologies perhaps showing the biggest effects, although these alterations are still emerging. Most of these indications have been provided by animal models, in particular the bovine species, due to its similarities to human early embryo development. Oocytes and embryos are highly sensitive to environmental stress in vivo and in vitro. Thus, during in vitro culture, a number of stressful conditions affect embryonic quality and viability, inducing subfertility and/or long-term consequences that may reach the offspring. A high proportion of the embryos produced in vitro are arrested at a species-specific stage of development during the first cell divisions. These arrested embryos do not show signs of programmed cell death during early cleavage stages. Instead, defective in vitro produced embryos would enter a permanent cell cycle arrest compatible with cellular senescence, in which they show active metabolism and high reactive oxygen species levels. Later in development, mainly during the morula and blastocyst stages, apoptosis would mediate the elimination of certain cells, accomplishing both a physiological role in to balancing cell proliferation and death, and a pathological role preventing the transmission of damaged cells with an altered genome. The latter would acquire relevant importance in in vitro produced embryos that are submitted to stressful environmental stimuli. In this article, we review the mechanisms mediating apoptosis and senescence during early embryo development, with a focus on in vitro produced bovine embryos. Additionally, we shed light on the protective role of senescence and apoptosis to ensure that unhealthy cells and early embryos do not progress in development, avoiding long-term detrimental effects.

The incompletely fulfilled promise of embryo transfer in cattle-why aren't pregnancy rates greater and what can we do about it?

Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

One-step automated bioprinting-based method for cumulus-oocyte complex microencapsulation for 3D in vitro maturation

Three-dimensional in vitro maturation (3D IVM) is a promising approach to improve IVM efficiency as it could prevent cumulus-oocyte complex (COC) flattening and preserve its structural and functional integrity. Methods reported to date have low reproducibility and validation studies are limited. In this study, a bioprinting based production process for generating microbeads containing a COC (COC-microbeads) was optimized and its validity tested in a large animal model (sheep). Alginate microbeads were produced and characterized for size, shape and stability under culture conditions. COC encapsulation had high efficiency and reproducibility and cumulus integrity was preserved. COC-microbeads underwent IVM, with COCs cultured in standard 2D IVM as controls. After IVM, oocytes were analyzed for nuclear chromatin configuration, bioenergetic/oxidative status and transcriptional activity of genes biomarker of mitochondrial activity (TFAM, ATP6, ATP8) and oocyte developmental competence (KHDC3, NLRP5, OOEP and TLE6). The 3D system supported oocyte nuclear maturation more efficiently than the 2D control (P<0.05). Ooplasmic mitochondrial activity and reactive oxygen species (ROS) generation ability were increased (P<0.05). Up-regulation of TFAM, ATP6 and ATP8 and down-regulation of KHDC3, NLRP5 expression were observed in 3D IVM. In conclusion, the new bioprinting method for producing COC-microbeads has high reproducibility and efficiency. Moreover, 3D IVM improves oocyte nuclear maturation and relevant parameters of oocyte cytoplasmic maturation and could be used for clinical and toxicological applications.

Consequences of assisted reproductive techniques on the embryonic epigenome in cattle

Procedures used in assisted reproduction have been under constant scrutiny since their inception with the goal of improving the number and quality of embryos produced. However, invitro production of embryos is not without complications because many fertilised oocytes fail to become blastocysts, and even those that do often differ in the genetic output compared with their invivo counterparts. Thus only a portion of those transferred complete normal fetal development. An unwanted consequence of bovine assisted reproductive technology (ART) is the induction of a syndrome characterised by fetal overgrowth and placental abnormalities, namely large offspring syndrome; a condition associated with inappropriate control of the epigenome. Epigenetics is the study of chromatin and its effects on genetic output. Establishment and maintenance of epigenetic marks during gametogenesis and embryogenesis is imperative for the maintenance of cell identity and function. ARTs are implemented during times of vast epigenetic reprogramming; as a result, many studies have identified ART-induced deviations in epigenetic regulation in mammalian gametes and embryos. This review describes the various layers of epigenetic regulation and discusses findings pertaining to the effects of ART on the epigenome of bovine gametes and the preimplantation embryo.

How can we improve embryo production and pregnancy outcomes of Holstein embryos produced in vitro? (12 years of practical results at a California dairy farm)

Genomic evaluations have revolutionized dairy cattle breeding, and the demand for embryos produced from very young heifers with high genetic merit has increased over time. The combination of low oocyte recovery, young age of donors, and milk production status can make the in vitro embryo production (IVP) of Holstein cattle incredibly challenging. Several factors need to be coordinated to obtain a live calf from an IVP embryo, but the quality of the oocyte at the start of the process is one of the key factors. Aspects related to oocyte quality, laboratory quality control, embryo quality and recipient selection are addressed here, based on the measures that the RuAnn Genetics Laboratory (Riverdale, California, USA) adopted in the last 12 years, with the goal of improving production of live, healthy calves from Holstein embryos. Follicular wave synchronization and stimulation with follicular stimulating hormone (FSH) is necessary to improve oocyte quality and consequently embryo production. Laboratory quality control and the use of high-quality supplies are essential to reduce variability in production and facilitate identification of other factors that might interfere with embryo production. High pregnancy rates can be achieved with good quality embryos selected at optimal time and stage of development, transferred by an experienced embryo transfer (ET) technician, to well managed recipients 7 or 8 days after estrus. Attention to detail at every step of the process is crucial to success.

Laser assisted blastomere extrusion biopsy of in vitro produced cattle embryos-A potential high throughput, minimally invasive approach for sampling pre-morula and morula stage embryos

Whilst adoption of in vitro production (IVP) of cattle embryos and subsequent biopsy for genetic evaluation is increasing, biopsy techniques primarily used were developed to sample in vivo-produced blastocysts. This study was conducted to develop a laser-assisted blastomere extrusion approach for rapid and minimal-invasive biopsy of IVP cattle embryos at pre-morula to morula stages of development (Day 5 or 6 post-fertilisation). Embryo development into blastocysts was not compromised when ≤3 cells were collected by blastomere extrusion on Day 5 (44.4 ± 4.4 % and 34.3 ± 4.6 %) or Day 6 (58.0 ± 4.3 % and 57.5 ± 5.3 %) post-fertilisation compared with non-biopsied control embryos. Similarly, capacity to withstand cryopreservation was not different between embryos biopsied at Day 5 and 6 post-fertilisation and control-embryos (58.8 ± 6.0 %, 63.5 ± 5.6 %, and 56.0 ± 4.8 %, respectively). When more cells were collected from embryos at Day 6 post-fertilisation (≥8 compared to ≤3 cells), subsequent embryo development was not different (63.6 ± 6.1 % and 73.1 ± 6.2 %, respectively) nor was the capacity to withstand cryopreservation (67.9 ± 9.0 % and 62.5 ± 8.7 %, respectively). For biopsies on Day 6 post-fertilization, 95 % of samples produced a PCR product; however, when compared to the whole embryo PCR results, approximately 11 % of biopsy-samples classified as being from a male embryo were from female embryos (false positive), indicating DNA contamination between samples. In conclusion, results of this study indicate laser-assisted blastomere extrusion is a time efficient and minimally invasive approach to biopsy IVP morula and pre-morula cattle embryos to facilitate genetic analysis.

Quantitative proteomic strategies to study reproduction in farm animals: Female reproductive fluids

Reproductive fluids from the female reproductive tract are gaining attention for their potential to support and optimize reproductive processes, including gamete maturation and embryo culture in vitro. Quantitative proteomics is a powerful way to decipher the proteome of reproductive tract fluids and to identify biologically relevant proteins. The present review describes proteomic strategies for analysing female reproductive fluid proteins. In addition, it considers the strategies for the preparation of oviductal, uterine and follicular fluid samples. Finally, it highlights the main results of quantitative proteomic studies, providing insights into the biological processes related to reproductive biology in farm animals. SIGNIFICANCE: Assisted reproductive technologies (ARTs) have become vitally important for farm animal breeding and much effort is going into the optimization and refinement of the techniques. There are also attempts to imitate physiological conditions by adding reproductive fluids or individual fluid proteins to improve in vitro procedures. A detailed knowledge of the reproductive fluid proteomes is indispensable. The present review summarizes the most widely used quantitative proteomic approaches for the analysis of fluids from the female reproductive tract and highlights the potential of quantitative proteomics to delineate reproductive processes and identify candidate proteins for ARTs in farm animals.

In vitro fertilization: productivity of donors of different bovine breeds

The objective of the present study was to evaluate efficiency of in vitro fertilization (IVF) in Nelore, Brangus, and Girolando oocyte donors. Ovum pickup (OPU) from the donors was conducted every 15 days to assess oocyte recovery, IVF, and post-transfer pregnancy percentage. For Nelore, the mean numbers of total and viable oocytes recovered (23.5 ± 1.1 and 14.0 ± 1.0, respectively) were higher (p < 0.05) than those for Brangus (12.7 ± 1.9 and 6.6 ± 1.0, respectively) and Girolando (12.5 ± 1.4 and 6.8 ± 0.7, respectively); Brangus and Girolando did not differ from each other (p > 0.05). The percentage of blastocyst production differed (p < 0.05) between Nelore (48.4 ± 2.4%), Brangus (40.3 ± 3.6%), and Girolando (38.9 ± 2.6%), but those in Brangus and Girolando did not differ (p > 0.05). The percentage of blastocysts (transferred) that resulted in pregnancy did not differ (p > 0.05) between Nelore (45.5 ± 3.8%), Brangus (41.7 ± 4.1%), and Girolando (40.7 ± 3.7%). Of the breeds studied, Nelore donors are more efficient for IVF, but conditions of this study.

Extracellular vesicles and its advances in female reproduction

Intercellular communication is an essential mechanism for development and maintenance of multicellular organisms. Extracellular vesicles (EVs) were recently described as new players in the intercellular communication. EVs are double-membrane vesicles secreted by cells and are classified according to their biosynthesis, protein markers and morphology. These extracellular vesicles contain bioactive materials such as miRNA, mRNA, protein and lipids. These characteristics permit their involvement in different biological processes. Reproductive physiology is complex and involves constant communication between cells. Different laboratories have described the presence of EVs secreted by ovarian follicular cells, oviductal cells, in vitro produced embryos and by the endometrium, suggesting that EVs are involved in the development of gametes and embryos, in animals and humans. Therefore, is important to understand physiological mechanisms and contributions of EVs in female reproduction in order to develop new tools to improve in vivo reproductive events and assisted reproductive techniques (ARTs). This review will provide the current knowledge related to EVs in female reproductive tissues and their role in ARTs.

In vitro fertilisation in domestic mammals-a brief overview

Many factors influence the final oocyte maturation, fertilisation, and early embryo development, and there are both similarities and differences between species. When comparing the advancement of assisted reproductive technologies (ARTs), the development in the bovine species is not far behind the medical front, with around one million in vitro-produced bovine embryos each year. This rate of progress is not seen in the other domestic species. This review aims to give an overview of the development and specific difficulties of in vitro embryo production in various domestic animal species, with the main focus on cows, pigs, and cats. In production animals, the aim of ARTs is commonly to increase the genetic progress, not to treat reproductive failure. The ARTs are also used for preservation of genetic diversity for the future. However, specifically for oocyte maturation, fertilisation, and early embryonic development, domestic mammals such as the cow and pig can be used as models for humans. This is particularly attractive from an animal welfare point of view since bovine and porcine oocytes are available in large numbers from discarded slaughterhouse material, thereby decreasing the need for research animals. Both for researchers on the animal and human medical fronts, we aim for the development of in vitro production systems that will produce embryos and offspring that are no different from those conceived and developed in vivo. Species-comparative research and development can provide us with crucial knowledge to achieve this aim and hopefully help us avoid unnecessary problems in the future.

Recent progress in bovine in vitro-derived embryo cryotolerance: Impact of in vitro culture systems, advances in cryopreservation and future considerations

Cryopreservation of in vitro-derived bovine embryos is a crucial step for the widespread reproduction and conservation of valuable high-merit animals. Given the current popularity of bovine in vitro embryo production (IVP), there is a demand for a highly efficient ultra-low temperature storage method in order to maximize donor ovum pickup (OPU) turn-over, recipient availability/utilization and domestic/overseas commercial trading opportunities. However, IVP bovine embryos are still very sensitive to chilling and cryopreservation, and despite recent progress, a convenient (simple and robust) protocol has not yet been developed. At the moment, there are two methods for bovine IVP embryo cryopreservation: slow programmable freezing and vitrification. Both of the aforementioned techniques have pros and cons. While controlled-rate slow cooling can easily be adapted for direct transfer (DT), ice crystal formation remains an issue. On the other hand, vitrification solved this problem but the possibility of successful DT commercial incorporation remains to be determined. Moreover, simplification of the vitrification protocol (including warming) through the use of an in-straw dilution without the use of a microscope is a prerequisite for its use under farm conditions. This review summarizes the bovine IVP embryo cryopreservation achievements, strengths and limitations of both freezing systems and prospective improvements to enhance cryosurvival, as well as perspectives on future directions of this assisted reproductive technology.

Fatty acid metabolism as an indicator for the maternal-to-zygotic transition in porcine IVF embryos revealed by RNA sequencing

A number of fatty acids have been found in porcine oocytes and early embryos. Recent studies have indicated the importance of fatty acids in the development of pre-implantation porcine embryos, whether derived from in vivo or somatic cell nuclear transfer. However, the effects of fatty acids on porcine embryos produced by in vitro fertilization (IVF) remain poorly defined. This study aimed to investigate the patterns of gene expression and functions of fatty acids in pre-implantation IVF porcine embryos at different stages using transcriptome sequencing. We found that, in IVF porcine embryos, genes related to fatty acid metabolism were positively expressed during early embryonic development. Additionally, the expression of genes related to lipid metabolism changed dramatically during the maternal-to-zygotic transition (MZT), and the genes associated with lipid metabolism were correlated with zygotic genome activation in porcine IVF embryos, suggesting that fatty acid metabolism plays an important role in MZT. In summary, fatty acid metabolism may be an indicator of MZT in porcine IVF embryos, which presents new considerations for exploring the regulatory mechanisms of this process.

Follicular wave synchronization prior to ovum pick-up

Among the reproductive biotechnologies, in vitro embryo production (IVEP) is an important tool for multiplying genetic material of superior merit. Recently, the number of embryos produced and transferred in vitro became significantly higher than that produced in vivo worldwide. In this context, the enhancement was attributable to ovum pick-up (OPU). With the advent of genomic technology, shortened breeding intervals, and increased selection accuracy, IVEP has attracted increasing attention for commercial use. The IVEP technique is well-established, but the embryo production rate has reached a plateau at 30-40%. Despite constant advances, the OPU/IVEP programs face some challenges that hinder the efficient application of the technique. Previous studies have shown that the quantity and quality of aspirated oocytes are essential factors for successful IVEP. This paper presents a brief overview of alternatives that can be employed to improve the process-seeking methods that assist in the recovery of better-quality oocytes and higher competence in OPU to improve embryo production. These strategies include using follicular wave synchronization prior to OPU, employing the influence of antral follicle populations, using the pre-OPU gonadotrophic stimulus and applying non-hormonal methods for selecting female donors.

Novel Techniques of Sperm Selection for Improving IVF and ICSI Outcomes

Almost 50% of the infertility cases are due to male factors. Assisted reproductive technologies (ARTs) allow to overcome the incapacity of these patients' spermatozoa to fertilize the oocyte and produce a viable and healthy offspring, but the efficiency of the different techniques has still the potential to improve. According to the latest reports of the European Society of Human Reproduction and Embryology (ESHRE) and the Centers for Disease Control and Prevention of the United States (CDC), the percentages of deliveries per ART cycle in 2014 and 2016 were 21 and 22%, respectively. Among the reasons for this relatively low efficiency, the quality of the spermatozoa has been pointed out as critical, and the presence of high percentages of DNA-damaged spermatozoa in patients' ejaculates is possibly one of the main factors reducing the ARTs outcomes. Thus, one of the main challenges in reproductive medicine is to ensure the highest quality of the spermatozoa used in ARTs, and specifically, in terms of genetic integrity. The latest techniques for the preparation and selection of human spermatozoa are herein discussed focusing on those proven to improve one or several of the following parameters: sperm genetic integrity, fertilization capacity, embryo production, and in vitro survival, as well as pregnancy and delivery rates following in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). In addition, we discuss the potential of techniques developed in non-human mammals that could be further transferred to the clinic.

Review: Recent advances in bovine in vitro embryo production: reproductive biotechnology history and methods

In vitro production (IVP) of embryos and associated technologies in cattle have shown significant progress in recent years, in part driven by a better understanding of the full potential of these tools by end users. The combination of IVP with sexed semen (SS) and genomic selection (GS) is being successfully and widely used in North America, South America and Europe. The main advantages offered by these technologies include a higher number of embryos and pregnancies per unit of time, and a wider range of potential female donors from which to retrieve oocytes (including open cyclic females and ones up to 3 months pregnant), including high index genomic calves, a reduced number of sperm required to produce embryos and increased chances of obtaining the desired sex of offspring. However, there are still unresolved aspects of IVP of embryos that limit a wider implementation of the technology, including potentially reduced fertility from the use of SS, reduced oocyte quality after in vitro oocyte maturation and lower embryo cryotolerance, resulting in reduced pregnancy rates compared to in vivo-produced embryos. Nevertheless, promising research results have been reported, and work is in progress to address current deficiencies. The combination of GS, IVP and SS has proven successful in the commercial field in several countries assisting practitioners and cattle producers to improve reproductive performance, efficiency and genetic gain.

Intensive use of IVF by large-scale dairy programs

The number of embryos produced by in vitro fertilization (IVF) has grown exponentially in recent years. Recently, for the first time, the number of embryos produced and transferred in vitro was significantly higher than the number developed in vivo worldwide. In this context, a particular boost occurred with ovum pick-up (OPU) and in vitro embryos produced in North America, and this technology is becoming more prominent for commercial dairy farms. However, despite many advances in recent decades, laboratories and companies are looking for methods and alternatives that can be used in collaboration with the existing process to improve it. Among the strategies used to improve the dairy industry are the use of genomic analysis for the selection of animals with desired traits or as an evaluation tool of oocyte and embryo quality, the optimization of the collection and use of gametes from prepubertal females and males, the effective use of sexed semen, and improvements in culture media and methods of embryo cryopreservation. Thus, this review aims to discuss the highlights of the commercial use of IVF and some strategies to increase the application of this technique in large-scale dairy programs.

Odf2 haploinsufficiency causes a new type of decapitated and decaudated spermatozoa, Odf2-DDS, in mice

Outer dense fibre 2 (Odf2 or ODF2) is a cytoskeletal protein required for flagella (tail)-beating and stability to transport sperm cells from testes to the eggs. There are infertile males, including human patients, who have a high percentage of decapitated and decaudated spermatozoa (DDS), whose semen contains abnormal spermatozoa with tailless heads and headless tails due to head-neck separation. DDS is untreatable in reproductive medicine. We report for the first time a new type of Odf2-DDS in heterozygous mutant Odf2+/- mice. Odf2+/- males were infertile due to haploinsufficiency caused by heterozygous deletion of the Odf2 gene, encoding the Odf2 proteins. Odf2 haploinsufficiency induced sperm neck-midpiece separation, a new type of head-tail separation, leading to the generation of headneck sperm cells or headnecks composed of heads with necks and neckless tails composed of only the main parts of tails. The headnecks were immotile but alive and capable of producing offspring by intracytoplasmic headneck sperm injection (ICSI). The neckless tails were motile and could induce capacitation but had no significant forward motility. Further studies are necessary to show that ICSI in humans, using headneck sperm cells, is viable and could be an alternative for infertile patients suffering from Odf2-DDS.

Oxidative homeostasis in oocyte competence for in vitro embryo development

The objective of this study was to evaluate the levels of reactive oxygen species (ROS) and glutathione (GSH) in oocytes from follicles of different diameters and their relevance in the in vitro production of embryos (IVPE). Bovine ovaries were aspirated according to the diameter of the follicle [2-8 (general), 4-8 (large), and 2 < 4 mm (small)]. The oocytes were evaluated for levels of ROS, GSH, in vitro maturation, and IVPE. Higher levels of ROS and GSH were observed (p < 0.05) in oocytes of the large group (85.6 ± 7.2 and 140.0 ± 9.6) followed by those in the general (81.1 ± 10.5 and 134.3 ± 7.8) and small (73.5 ± 10.1 and 125.0 ± 10.6) groups. However, the proportion of ROS/GSH did not differ (p > 0.05) between the general, large, and small groups. The maturation was higher (p < 0.05) in the large group (87.8 ± 3.0%) than in the small group (72.2 ± 5.8%), but both were similar (p > 0.05) to that in the general group (82.2 ± 2.5%), whereas the IVPE of the large group (57.3 ± 3.0%) was higher (p < 0.05) than those in the general (44.7 ± 4.4%) and small (34.0 ± 4.0%) groups. We report that oocytes from large follicles are more competent for IVPE, whereas higher levels of ROS and GSH appear to be correlated with oocyte competence, as long as oxidative homeostasis is retained.

BOARD INVITED REVIEW: Post-transfer consequences of in vitro-produced embryos in cattle

In vitro embryo production (IVP) in cattle has gained worldwide interest in recent years, but the efficiency of using IVP embryos for calf production is far from optimal. This review will examine the pregnancy retention rates of IVP embryos and explore causes for pregnancy failures. Based on work completed over the past 25 yr, only 27% of cattle receiving IVP embryos will produce a live calf. Approximately 60% of these pregnancies fail during the first 6 wk of gestation. When compared with embryos generated by superovulation, pregnancy rates are 10% to 40% lower for cattle carrying IVP embryos, exemplifying that IVP embryos are consistently less competent than in vivo-generated embryos. Several abnormalities have been observed in the morphology of IVP conceptuses. After transfer, IVP embryos are less likely to undergo conceptus elongation, have reduced embryonic disk diameter, and have compromised yolk sac development. Marginal binucleate cell development, cotyledon development, and placental vascularization have also been documented, and these abnormalities are associated with altered fetal growth trajectories. Additionally, in vitro culture conditions increase the risk of large offspring syndrome. Further work is needed to decipher how the embryo culture environment alters post-transfer embryo development and survival. The risk of these neonatal disorders has been reduced by the use of serum-free synthetic oviductal fluid media formations and culture in low oxygen tension. However, alterations are still evident in IVP oocyte and embryo transcript abundances, timing of embryonic cleavage events and blastulation, incidence of aneuploidy, and embryonic methylation status. The inclusion of oviductal and uterine-derived embryokines in culture media is being examined as one way to improve the competency of IVP embryos. To conclude, the evidence presented herein clearly shows that bovine IVP systems still must be refined to make it an economical technology in cattle production systems. However, the current shortcomings do not negate its current value for certain embryo production needs and for investigating early embryonic development in cattle.

Expression dynamics of Integrin Subunit Beta 5 in bovine gametes and embryos imply functions in male fertility and early embryonic development

Integrins have been shown to act as signalling receptors, and they primarily recognise extracellular matrix ligands on the oocyte surface. However, their possible roles in oocyte activation and embryo development are not clearly understood. The objectives of this study were to evaluate expression of Integrin Subunit Beta 5 (ITGβ5) in bovine sperm, oocytes, and early embryos and to ascertain the evolutionary conservation of ITGβ5. To accomplish these objectives, we used western blotting to study expression levels of ITGβ5 protein in sperm and RT-qPCR to determine expression levels of ITGβ5 transcripts in oocytes and embryos. We have also used bioinformatic analysis to determine the evolutionary conservation of the ITGβ5 protein among various species. Western blotting showed that ITGβ5 protein was detectable in bull sperm. Moreover, results of RT-qPCR showed that levels of ITGβ5 were significantly higher in the two-cell embryos, followed by the 8-16-cell embryos. However, no significant difference in expression levels were noted for the morula and blastocyst stages as compared to MII oocytes. Bioinformatic analysis revealed that ITGβ5 is conserved among various species. We conclude that expression of ITGβ5 in bovine gametes and embryos implies an important role in fertilisation and embryogenesis.

Efficient in vitro embryo production using in vivo-matured oocytes from superstimulated Japanese Black cows

We examined whether the use of in vivo-matured oocytes, collected by ovum pick-up (OPU) from superstimulated Japanese Black cows, can improve the productivity and quality of in vitro produced embryos. The cows were superstimulated by treatment with progesterone, GnRH, FSH and prostaglandin F2α according to a standardized protocol. The resulting in vivo-matured oocytes were collected by OPU and used subsequently for the other experiments. The immature oocytes from cows in the non-stimulated group were collected by OPU and then subjected to maturation in vitro. We found that the rate of normally distributed cortical granules of the matured oocyte cytoplasm in the superstimulated group was significantly higher than that in the non-stimulated group. The normal cleavage rate (i.e., production of embryos with two equal blastomeres without fragmentation) and freezable blastocyst rate were significantly higher in the superstimulated group than in the non-stimulated group. Among the transferable blastocysts, the ratio of embryos from normal cleavage was also significantly higher in the superstimulated group than in the non-stimulated group. For in vivo-matured oocytes, it was observed that the pregnancy rates were significantly higher when normally cleaved embryos were used for transfer. Taken together, these results suggest that high-quality embryos with respect to developmental kinetics can be efficiently produced with the use of in vivo-matured oocytes collected by OPU from superstimulated Japanese Black cows.