Resumo em Inglês:

Abstract Reproductive biotechniques in the equine species have advanced in the last decade and horse breeders have started to question the possibilities of interfering in the determination of foal sex. The aim of the present study was to verify whether the variables mares and stallion’s age, side of the ovary containing the preovulatory follicle, preovulatory follicle diameter, time between breeding and ovulation, and ovulation inducing hormones influence the sex of the foal. A total of 259 reproductive cycles of 160 mares and 22 Thoroughbred stallions were used. Statistical analysis was performed using R software, including Pearson's chi-square test and logistic regression. Of the total foals born, 136 were males (52.51%) and 123 were females (47.49%). In mares that ovulated with -24h after ovulation induction, 104 foals (54.74%) were males and 86 (45.26%) were females, while in mares that ovulated with +24h, 32 foals (46.38%) were males and 37 (53.62%) were females. Stallions up to 15 years old had 44.14% (n=49) females and those over 15 years had 49.66% (n=73) females. The simple logistic regression model showed that mares and stallions under 15 years old, mares with ovulation time less than 24 hours and treated with Deslorelin had a higher probability of having male foals, but the Pearson's chi-square test showed that foals gender were not influenced by the variables studied.

Resumo em Inglês:

Abstract The effects of antibiotics on sperm longevity in collared peccary (Pecari tajacu) fresh diluted semen was evaluated. Semen samples from six adult males were collected by electroejaculation and diluted in Tris-citrate-fructose alone (control) and plus streptomycin-penicillin (2 mg/ml-2000 IU/ml) or gentamicin (70 µg/ml). Membrane integrity and functionality, mitochondrial activity and sperm morphology were assessed subjectively. Sperm motility and other kinetic parameters were objectively assessed using CASA (computer-assisted semen analysis). The semen diluted according to the treatments were submitted to the thermoresistance test, incubated at 37 ° C, and the sperm parameters analyzed at 0, 30, 60, 120 and 180 min. The average values of the treatments were compared with each other and between the times. There were no differences (P > 0.05) between treatments until the end of the test. Control and streptomycin-penicillin samples maintained sperm function for up to 180 min (with total motility of 24.3 ± 7.1% and 28 ± 8.7%, respectively). Gentamicin aliquots retained most parameters until the end of the incubation, except for membrane integrity and mitochondrial activity that declined (P < 0.05) at 180 min (53.1 ± 7.1% and 50.7 ± 6.2%, respectively) compared to 0 min (80.5 ± 4.7% and 86.3 ± 3.4%, respectively). In conclusion, a multiparametric thermoresistance test proved that Tris-based extenders used for collared peccary semen can be effectively supplemented by streptomycin-penicillin (2 mg/ml-2000 IU/ml) or gentamicin (70 µg/ml), especially during 180-min incubation at 37 °C.

Resumo em Inglês:

Abstract In 2024, the Brazilian College of Animal Reproduction (CBRA in Portuguese) is proudly celebrating its golden 50th anniversary. Founded in 1974, CBRA has had a very productive and challenging journey of five decades, achieving many important milestones that have established it as a major society and its journal as a major reference in the field of animal reproduction, both in Brazil and internationally. Coincidentally, the Animal Reproduction journal and the International Symposium on Animal Biology (ISABR), both created and sponsored by CBRA, are also celebrating their 20th and 10th anniversary and edition, respectively, this year. These remarkable events are being celebrated in the city of Fortaleza, Brazil, during the 10th edition of ISABR. As someone who had the privilege of playing a leading role in the creation and establishment of both Animal Reproduction journal and ISABR, I am honored to describe here the favorable circumstances that led to these significant achievements. The crucial steps and combined efforts required to make these institutions successful were unconditionally supported by the CBRA. Additionally, significant global networking and scientific collaborations, both individual and collective, have been pivotal in advancing the science and connecting the scientific community, spanning both young and experienced members, for decades. Finally, I hope that this historical article will inspire future generations of scientists in the field to continue CBRA’s journey and leadership, ensuring the growth of Animal Reproduction and ISABR advancement to even higher standards.

Resumo em Inglês:

Abstract The female reproductive function is coordinated by the endocrine system driven by the hypothalamic-pituitary-gonadal (HPG) axis. While not directly part of the female reproductive system, the gut microbiome plays a crucial role in overall health, including reproductive health. The gut microbiome communicates bidirectionally with the brain via the gut-brain axis, influencing stress levels, mood, and hormonal balance, which can impact reproductive health and fertility. In addition to that, the vaginal and uterine microbiome are directly involved with the reproductive success of farm animals, including female fertility and offspring development. In this paper, we summarize some of the effects of bacterial contamination in the female reproductive tract and their association with reproductive performance in farm animals.

Resumo em Inglês:

Abstract The objective of the present study was to transpose sperm freezing methodology from domestic goat to the Tadjik markhor (Capra falconeri heptneri) and to address the feasibility to develop IVP and artificial insemination using such frozen semen. Semen of different adult markhor males were successfully recovered by electro-ejaculation and were then frozen using caprine methodology. Frozen semen showed good survival rates at thawing and good fertility rates were assessed in heterologous in vitro fertilization system with goat oocytes. LOPU/IVF was applied for Tadjik markhor females allowing the first successful blastocyst production in vitro. In an applied program, we also transposed successfully intrauterine AI method with frozen/thawed semen to the Tadjik markhor.

Resumo em Inglês:

Abstract This study explored the migration of follicular fluid (FF)-derived extracellular vesicles (EVs) of the uterine environment to the bloodstream and their interaction with neutrophils in vivo and in vitro. For the in vivo experiment, six Nellore heifers (Bos indicus) received an intrauterine infusion seven days after ovulation with 1X PBS only (sham group; n=1), 1X PBS stained with lipophilic dye PKH26 (control group; n=2), or FF-derived EVs stained with PKH26 (treated group; n=3). Plasma was collected at 0, 10, 30, 60-, 180-, 360-, 720-, and 1440-min post-infusion to obtained EVs for analysis by nano flow cytometry. Labeled EVs were present in the bloodstream at 30- and 60-min post-infusion in the treatment group. Additionally, plasma derived-EVs from all groups were positive for Calcein-AM, Alix, Syntenin, and Calnexin, which confirm the presence of EVs. The second experiment utilized the plasma-derived EVs from the heifers from 30 and 60 min timepoints to evaluate if neutrophils can uptake EVs in vitro. As results, it was possible to observe the presence of labeled EVs in neutrophils treated with plasma derived-EVs from the treatment group. In summary, our results suggest that labeled EVs can migrate from the uterine environment rapidly and interact with circulating immune cells in bovine.

Resumo em Inglês:

Abstract The oviduct and uterus provide an optimal environment for early embryo development, where effective communication between the embryo and the maternal reproductive tract is crucial for establishing and maintaining pregnancy. Oviductal and uterine-derived EVs play pivotal roles in this maternal-embryonic communication and in facilitating early embryo development. However, despite the ability of in vitro culture methods to produce viable embryos, the lack of exchange between the embryo and the mother often results in lower-quality embryos than those derived in vivo. Therefore, there is a pressing need to increase our understanding of the physiological mechanisms underlying embryo interaction with the oviduct and endometrium through EVs and to develop models capable of mimicking the in vivo environment. This review aims to provide up-to-date insights into the communication between the mother and pre-implantation bovine embryo, exploring their applications and perspectives in the field.

Resumo em Inglês:

Abstract The path to fertility in the mare requires an understanding of the hormonal influences, the immune response, genetics, and epigenetic mechanisms involved not only in physiological reproductive processes, but also such pathologies as endometritis and endometrosis. Endometritis may lead to endometrosis establishment. In the presence of endometritis, neutrophils arrive at the mare endometrium, and form neutrophil extracellular traps. While NETosis plays pivotal roles, prolonged inflammation can lead to chronic endometritis, endometrosis, and fertility issues. Matrix metalloproteinases and epigenetic changes influence the course of endometrosis. Inhibitors of specific enzymes involved in NETosis and epigenetic inhibitors have shown potential in reducing pro-fibrotic effects. Collagen type III (COL3) has emerged as a putative biomarker, correlating with endometrosis and useful in fertility assessment. Thus, COL3 may offer a non-invasive diagnostic tool, as a complement to histopathological methods. Epigenetic modifications and miRNA expressions offer new avenues for therapeutic strategies, emphasizing the importance of understanding the cellular mechanisms at play in mare endometrial fibrosis.

Resumo em Inglês:

Abstract Gene editing technologies have revolutionized the field of livestock breeding, offering unprecedented opportunities to enhance animal welfare, productivity, and sustainability. This paper provides a comprehensive review of recent innovations and applications of gene editing in livestock, exploring the diverse applications of gene editing in livestock breeding, as well as the regulatory and ethical considerations, and the current challenges and prospects of the technology in the industry. Overall, this review underscores the transformative potential of gene editing in livestock breeding and its pivotal role in shaping the future of agriculture and biomedicine.

Resumo em Inglês:

Abstract Embryonic stem cells (ESCs) have proven to be a great in vitro model that faithfully recapitulates the events that occur during in vivo embryogenesis, making them a unique tool to study the cellular and molecular mechanisms that define tissue specification during embryonic development. Livestock ESCs are particularly attractive and have broad prospects including drug selection and human disease modeling, improvement of reproductive biotechniques and agriculture-related applications such as production of genetically modified animals. While mice and human ESCs have been established many years ago, no significant advances were made in livestock species until recently. Nowadays, livestock ESCs are available from cattle, pigs, sheep, horses and rabbits with different states of pluripotency. In this review, we summarize the current advances on livestock ESCs establishment and maintenance along with their present and future applications.

Resumo em Inglês:

Abstract For nearly 100 years the postcoital inflammatory response has been described in the female reproductive tract of rodents. Since the 1950’s this observation has been made in a number of animals including humans and domestic species. Yet pregnancy can be initiated and maintained by using embryo transfer which bypasses insemination and the related postcoital inflammatory response. Thus, the role of semen exposure beyond sperm transport and subsequent postcoital inflammatory response in female reproductive tissues has yet to be given a true physiological purpose. Historically the postcoital inflammatory response of female tissues was suggested to remove spermatozoa and male derived pathogens from the female reproductive tract. More recently, semen exposure and the postcoital inflammatory response have been suggested to play a role in long-term preparation of the maternal immune system to the semi-allogeneic pregnancy, ancillary support of the preimplantation embryo, and potentially fetal programing that improves pregnancy outcomes, while the absence or inappropriate postcoital inflammation has been suggested to contribute to pregnancy complications. Although the postcoital inflammatory response has been robustly characterized, the evidence for its role in promoting positive pregnancy outcomes or reducing pregnancy complications remains tenuous. This manuscript is designed to balance the information we know regarding semen exposure and postcoital inflammation in various animal systems, with the information we perceive to be factual but perhaps not yet fully tested, along with the data we have yet to generate if we intend to postulate a physiological purpose of the postcoital inflammatory response to pregnancy outcomes.

Resumo em Inglês:

Abstract Assisted reproductive technologies (ART) are fundamental for cattle breeding and sustainable food production. Together with genomic selection, these technologies contribute to reducing the generation interval and accelerating genetic progress. In this paper, we discuss advancements in technologies used in the fertility evaluation of breeding animals, and the collection, processing, and preservation of the gametes. It is of utmost importance for the breeding industry to select dams and sires of the next generation as young as possible, as is the efficient and timely collection of gametes. There is a need for reliable and easily applicable methods to evaluate sexual maturity and fertility. Although gametes processing and preservation have been improved in recent decades, challenges are still encountered. The targeted use of sexed semen and beef semen has obliterated the production of surplus replacement heifers and bull calves from dairy breeds, markedly improving animal welfare and ethical considerations in production practices. Parallel with new technologies, many well-established technologies remain relevant, although with evolving applications. In vitro production (IVP) has become the predominant method of embryo production. Although fundamental improvements in IVP procedures have been established, the quality of IVP embryos remains inferior to their in vivo counterparts. Improvements to facilitate oocyte maturation and development of new culture systems, e.g. microfluidics, are presented in this paper. New non-invasive and objective tools are needed to select embryos for transfer. Cryopreservation of semen and embryos plays a pivotal role in the distribution of genetics, and we discuss the challenges and opportunities in this field. Finally, machine learning (ML) is gaining ground in agriculture and ART. This paper delves into the utilization of emerging technologies in ART, along with the current status, key challenges, and future prospects of ML in both research and practical applications within ART.

Resumo em Inglês:

Abstract In beef cattle operations that conduct embryo transfer, the overall success depends on the pregnancy outcome that results from every pregnancy opportunity. In this review, we dissected the main components that determine if a recipient will sustain the pregnancy after embryo transfer up to calving. Specifically, we describe the effect of the uterus on its ability to provide a receptive environment for embryo development. We then discuss the capacity of the embryo to thrive after transfer, and especially the contribution of the sire to embryo fitness. Finally, we review the interaction between the uterus and the embryo as an integrated unit that defines the pregnancy.

Resumo em Inglês:

Abstract Reproductive maturation is a complex physiological process controlled by the neuroendocrine system and is characterized by an increase in gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) pulsatile secretion. Nutrition during early development is a key factor regulating puberty onset, which is defined as first ovulation in females. In heifers, nutrient restriction after weaning delays puberty, whereas elevated levels of nutrition and energy reserves advance reproductive maturation. Recent studies in cattle and other animal models have shown that the dam’s nutrition during gestation can also program the neuroendocrine system in the developing fetus and has the potential to alter timing of puberty in the offspring. Among the metabolic signals that modulate brain development and control timing of puberty is leptin, a hormone produced primarily by adipocytes that communicates energy status to the brain. Leptin acts within the arcuate nucleus of the hypothalamus to regulate GnRH secretion via an upstream network of neurons that includes neurons that express neuropeptide Y (NPY), an orexigenic peptide with inhibitory effects on GnRH secretion, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide with excitatory effects on GnRH neurons. Another important population of neurons are KNDy neurons, neurons in the arcuate nucleus that co-express the neuropeptides kisspeptin, neurokinin B, and dynorphin and have strong stimulatory effects on GnRH secretion. Our studies in beef heifers indicate that increased nutrition between 4 to 8 months of age advances puberty by diminishing NPY inhibitory tone and by increasing excitatory inputs of αMSH and kisspeptin, which collectively lead to increased GnRH/LH pulsatility. Our ongoing studies indicate that different planes of nutrition during gestation can alter maternal leptin concentrations and promote changes in the fetal brain. Nonetheless, at least in Bos indicus-influenced heifers, deficits programmed prenatally can be overcome by adequate postnatal nutrition without negatively impacting age at puberty or subsequent fertility.

Resumo em Inglês:

Abstract Pregnancy losses negatively affect the cattle industry, impacting economic indices and consequently the entire production chain. Early embryonic failure has been an important challenge in the embryo industry because proper identification of embryo death at the beginning of gestation is difficult. This review aimed to provide a better understanding on reproductive failure and the relationship between early embryonic loss and different reproductive biotechniques. This review also considers insights and possible strategies for reducing early embryonic loss. The strategies addressed are as follows: i) great impact of rigorous embryo evaluation on reducing embryo losses; ii) selection of recipients at the time of transfer, taking into account health and nutritional status, and classification of the corpus luteum using ultrasound, either in area or vascularization; and iii) paternal effect as one of the factors that contribute to pregnancy losses, with a focus on embryo transfer.

Resumo em Inglês:

Abstract Selection strategies are performed post-fertilization when the random combination of paternal and maternal genomes has already occurred. It would be greatly advantageous to eliminate meiotic uncertainty by selecting genetically superior gametes before fertilization. To achieve this goal, haploid embryonic cells and embryonic stem cell lineages could be derived, genotyped, and used to substitute gametes. On the paternal side, androgenetic development can be achieved by removing the maternal chromosomes from the oocyte before or after fertilization. We have shown that once developed into an embryo, haploid cells can be removed for genotyping and, if carrying the selected genome, be used to replace sperm at fertilization. A similar strategy can be used on the maternal side by activating the oocyte parthenogenetically and using some embryonic cells for genotyping while the remaining are used to produce diploid embryos by fertilization. Placed together, both androgenetic and parthenogenetic haploid cells that have been genotyped to identify optimal genomes can be used to produce offspring with predetermined genomes. Successes and problems in developing such a breeding platform to achieve this goal are described and discussed below.

Resumo em Inglês:

Abstract Sperm quality is essential to guarantee the success of assisted reproduction. However, selecting high-quality sperm and maintaining it during (cryo)preservation for high efficiency remains challenging in livestock reproduction. A comprehensive understanding of sperm biology allows for better assessment of sperm quality, which could replace conventional sperm analyses used today to predict fertility with low accuracy. Omics approaches have revealed numerous biomarkers associated with various sperm phenotypic traits such as quality, survival during storage, freezability, and fertility. At the same time, nanotechnology is emerging as a new biotechnology with high potential for use in preparing sperm intended to improve reproduction in livestock. The unique physicochemical properties of nanoparticles make them exciting tools for targeting (e.g., sperm damage and sexing) and non-targeting bioapplications. Recent advances in sperm biology have led to the discovery of numerous biomarkers, making it possible to target specific subpopulations of spermatozoa within the ejaculate. In this review, we explore potential biomarkers associated with sperm phenotypes and highlight the benefits of combining these biomarkers with nanoparticles to further improve sperm preparation and technology.

Resumo em Inglês:

Abstract In cattle, artificial insemination (AI) is a technique that allows breeding by depositing frozen-thawed and extended semen into the female reproductive tract. The semen contains sperm with various motility patterns including dead, progressive and hyperactivated. Sperm hyperactivation is high amplitude, asymmetrical beating of sperm tail which usually occurs in the oviduct as part of the capacitation process, but it can also be induced by cryopreservation. After insemination, sperm enter the uterine glands and trigger a pro-inflammatory response in the uterus. Hyperactivated sperm, stimulated by sperm-Toll-like receptor 2 (TLR2), penetrates the mucus and uterine glands more efficiently and enhances the immune response. This facilitates the clearance of excess and dead sperm from the uterus. Some sperm escape the immune response and reach the oviduct either before or after the immune response is initiated. In the oviduct, sperm bind to the epithelium and form a reservoir. This triggers an anti-inflammatory response and preserves the fertilization potential of sperm. Hyperactivation facilitates sperm detaching from the epithelium, swimming through the viscous mucus and cumulus cells, and penetrating the egg's zona pellucida. Sperm-TLR2 activation enhances Ca2+-influx and acrosome reaction, which enables sperm to penetrate and fertilize oocytes during in vitro fertilization. Altogether, post-AI in cattle, sperm and maternal immunity interact differentially depending upon the site of sperm hyperactivation – whether it occurs within the uterus or oviduct. Specifically, hyperactivated sperm that enter the uterus after AI or are triggered via sperm-TLR2 activation or other stimuli contribute to sperm-induced uterine inflammation. Such hyperactivated sperm may impede their capacity to ascend to the oviduct. Conversely, sperm that become hyperactivated within the oviduct modulate their interactions with the oviduct and oocytes, which is pivotal during fertilization process. Indeed, the location and timing of sperm hyperactivation partially via TLR2 activation are critical determinants of their different influence on fertility.

Resumo em Inglês:

Abstract With the development of in vitro technologies, embryos can be produced using oocytes retrieved directly from the ovaries, i.e., regardless of ovulation. This has allowed the use of different animal categories as oocyte donors, including prepubertal cattle. The advantages of using this strategy to shorten the generation interval and accelerate genetic gain over time were soon recognized, and the first offspring generated using oocytes collected from calves were born in the early 1990s. Nevertheless, embryo production from calves and prepubertal heifers remains a challenge. The oocytes collected before puberty present low in vitro developmental potential, and the subsequent blastocyst rates are consistently lower than those from pubertal females. The acquisition of developmental competence by the oocytes occurs progressively throughout the prepubertal period, which can be subdivided into an early, intermediate, and late prepubertal (or peripubertal) phases, each characterized by different physiological and endocrine features. Therefore, embryo yield increases with age but will only achieve its maximum after puberty. The most common strategy to improve oocyte developmental potential before puberty is the use of gonadotrophic stimulation prior to oocyte retrieval. The results with superstimulation, however, vary among studies, depending on the source, dose, and length of FSH treatment, as well as the age and breed of the donors. The use of calves and prepubertal heifers as oocyte donors should also consider the possible impacts of the oocyte retrieval technique (LOPU or OPU) and the use of exogenous hormones on their subsequent fertility and productive life.

Resumo em Inglês:

Abstract Embryo transfer in cattle is an increasingly important technique for cattle production. Full attainment of the benefits of the technology will depend on overcoming hurdles to optimal performance using embryos produced in vitro. Given its importance, embryo technology research should become a global research priority for animal reproduction science. Among the goals of that research should be developing methods to increase the proportion of oocytes becoming embryos through optimization of in vitro oocyte maturation and in vitro fertilization, producing an embryo competent to establish and maintain pregnancy after transfer, and increasing recipient fertility through selection, management and pharmacological manipulation. The embryo produced in vitro is susceptible to epigenetic reprogramming and methods should be found to minimize deleterious epigenetic change while altering the developmental program of the resultant calf to increase its health and productivity. There are widening opportunities to rethink the technological basis for much of the current practices for production and transfer of embryos because of explosive advances in fields of bioengineering such as microfluidics, three-dimensional printing of cell culture materials, organoid culture, live-cell imaging, and cryopreservation.

Resumo em Inglês:

Abstract This review elucidates the physiological and endocrinological processes intrinsic to puberty and ovulation induction protocols in Bos indicus and Bos taurus beef heifers. Puberty is a complex physiological event involving gonadotropic and metabolic changes that lead to sexual maturity, first ovulation, and regular reproductive cycles, enabling females to reproduce. Exposure to progesterone-based hormonal protocols, with or without additional hormones, can reduce the age at first ovulation and improve sexual maturity through stimuli in the hypothalamus-pituitary-gonadal (HPG) axis and uterine development. However, inducing puberty differs from inducing ovulation, as it does not ensure the heifer will continue cycling or be ready to establish and maintain pregnancy after hormonal exposure. Regardless of the pharmacological basis, studies consistently report that beef heifers that had a corpus luteum (CL) prior to the timed-artificial insemination (TAI) protocol, have greater expression of estrus in response to synchronization and greater pregnancy per AI compared to heifers without a CL. The combination of P4 and E2 significantly impacts uterine development, increasing reproductive efficiency. Exposure to P4 causes a positive effect on inducing ovulation. However, studies indicate that the addition of E2 esters at the time of P4 device removal increases the ovulation rate. In general, the studies showed that fertility varied according to the type of the ovulation induction protocol used, but with inconsistent results. Although ovulation induction protocols are strategic tools to accelerate sexual maturity, a holistic view of the entire system is extremely important, combining integration with genetics and nutrition to enhance the reproductive outcomes of beef heifers. Future research is needed to understand and refine these protocols, driving the efficiency of beef cattle production systems.

Resumo em Inglês:

Abstract The reproductive efficiency of the herd is correlated with higher productivity in livestock. Reproduction biotechniques, such as ovulation synchronization protocols, are important to optimize production and accelerate genetic profit in beef and dairy herds. The objective of this review is to describe the evolution over the last 40 years of the artificial insemination (AI) and the timed-AI (TAI) protocols in cattle from a Brazilian perspective. TAI protocols are based on synchronizing emergence of the wave of follicular growth, controlling circulating progesterone (P4) concentrations, stimulating the final growth of the follicle and inducing a synchronized ovulation. Hormonal alternatives that optimize the response at the end of the protocol and strategies to induce final follicle growth and ovulation in categories of females with low expression of estrus are described. Furthermore, the potential positive effect of previous exposure to injectable P4 on fertility of Bos indicus and Bos taurus cows is also discussed.

Resumo em Inglês:

Abstract Embryo transfer is just one of a range of assisted reproductive technologies – often the last one in a sequence of others – that has revolutionised the cattle breeding industry. The number of in vitro-produced embryos transferred annually now surpasses the number derived by traditional superovulation by a factor of four. Although issues with cryotolerance of IVP embryos, embryo loss, and, in some cases, calf birth weight remain to be fully resolved, IVP embryos are likely here to stay as a tool for genetic improvement in dairy herds, offering increased flexibility in sire usage allowing multiple pregnancies from elite dam-bull combinations to be generated and the ability to produce more embryos per unit time than traditional superovulation. What follows is a short personal look back at the last 30 years; if you are looking for deep insights into the underlying biology regulating embryo development, this is not the place to look! Please refer to some of the excellent recent reviews and research papers cited herein.

Resumo em Inglês:

Abstract Over the past 40 years, assisted reproductive technologies (ARTs) have grown significantly in scale and innovation, from the bovine embryo industry’s shift from in vivo derived to in vitro produced embryos and the development of somatic cell-based approaches for embryo production. Domestic animal models have been instrumental in the development of ARTs for wildlife species in support of the One Plan Approach to species conservation that integrates in situ and ex situ population management strategies. While ARTs are not the sole solution to the biodiversity crisis, they can offer opportunities to maintain, and even improve, the genetic composition of the captive and wild gene pools over time. This review focuses on the application of sperm and embryo technologies (artificial insemination and multiple ovulation/in vitro produced embryo transfer, respectively) in wildlife species, highlighting impactful cases in which significant progress or innovation has transpired. One of the key messages following decades of efforts in this field is the importance of collaboration between researchers and practitioners from zoological, academic, governmental, and private sectors.

Resumo em Inglês:

Abstract This conference celebrates the 40th anniversary of AETE. Over the past 40 years, AETE has served as a forum for scientists, practitioners, and students working in assisted animal reproduction in livestock species. AETE conferences have reflected developments in the field, from basic to applied science, as well as regulatory changes in assisted animal reproduction practices. Europe has led the way in these developments for many years, progressing from artificial insemination, embryo transfer, and cryopreservation to semen sexing, in vitro production of embryos, cloning by nuclear transfer, genomic selection, and the rescue of highly endangered species. These significant contributions were made possible by the support of funding agencies, both at the national and European levels, promoting cooperation between scientists and practitioners. Assisted reproduction, and animal breeding more generally, face opposition from various groups, including animal rights activists, vegetarians, proponents of organic farming, environmentalists, certain political parties, and increasing regulatory burdens. These challenges seriously affect funding for scientific research, the work of practitioners, and the breeding industry as a whole. It is crucial to invest time and resources in communication to remind the public, politicians, and regulators of the achievements in this field and the contributions made to the food supply chain and the care of the rural and natural environment.

Resumo em Inglês:

Abstract In vitro produced embryos exhibit lower viability compared to their in vivo counterparts. Mammalian preimplantation embryos have the ability to reach the blastocyst stage in diverse culture media, showcasing considerable metabolic adaptability, which complicates the identification of optimal developmental conditions. Despite embryos successfully progressing to the blastocyst stage, adaptation to suboptimal culture environments may jeopardize blastocyst viability, cryotolerance, and implantation potential. Enhancing our capacity to support preimplantation embryonic development in vitro requires a deeper understanding of fundamental embryo physiology, including preferred metabolic substrates and pathways utilized by high-quality embryos. Armed with this knowledge, it becomes achievable to optimize culture conditions to support normal, in vivo-like embryo physiology, mitigate adaptive stress, and enhance viability. The objective of this review is to summarize the evolution of culture media for bovine embryos, highlighting significant milestones and remaining challenges.

Resumo em Inglês:

Abstract The productivity of the beef and dairy industries depends directly on the reproductive efficiency and genetic gain of the herd, which are directly associated with the appropriate use of Assisted Reproductive Technologies (ARTs). The objective of this review is to show from a Brazilian perspective the evolution over the last 40 years of ARTs related to ovulation resynchronization programs and embryo transfer in cattle. Despite significant improvements and high fertility obtained in timed artificial insemination (TAI) protocols (Sales et al., 2024 - Part I), the improvement of the use of in vitro-produced embryos, development of resynchronization programs, and the advance in Doppler ultrasonography (Doppler-US) for reproductive assessments of bovine females were the ARTs that presented the greatest relevance on reproductive effectiveness in cattle. In the last seven years, the embryo transfer (ET) technology using in vitro-produced (IVP) embryos took over the conventional ET of in vivo produced embryos after donor’s superovulation. Also, procedures and pregnancy rates after ET of IVP embryos were improved in dairy and beef operations. The Doppler-US allows the identification of non-pregnant females at an early stage based on the evaluation of blood perfusion of the corpus luteum. Recent studies in beef and dairy cows indicate satisfactory accuracy when Doppler-US is used at 20-22 days after TAI. Consequently, super-early resynchronization programs have been developed and are being implemented in commercial programs, thereby facilitating earlier conception through the use of semen from superior bulls, providing genetic and economic improvements in herds. Likewise, the assessment of luteal function by Doppler-US allows the selection of embryo recipients with greater receptivity, and consequently may increase the effectiveness of timed ET programs.