Animal Reproduction最新文献

This review examines the growing challenge of managing overabundant wildlife populations in the context of increasing human-wildlife conflicts. Traditionally, population control has relied on lethal methods such as culling, but these approaches are increasingly restricted due to concerns over environmental harm, non-target effects, human safety, and shifting societal values favouring more humane solutions. Fertility control has emerged as a promising non-lethal alternative, aiming to regulate populations by reducing reproductive success rather than increasing mortality. Its effectiveness depends on species-specific life-history traits: it can rapidly reduce populations of short-lived, highly fecund species, while effects in long-lived animals are delayed. Various fertility control methods are available, including endocrine suppression, immunocontraceptive vaccines, synthetic hormones and non-endocrine approaches such as zona pellucida vaccines. A major limitation to field applications of fertility control is the development of efficient delivery systems, particularly for small or free-ranging species where oral delivery must overcome challenges of palatability, stability, and species-specificity. Animal welfare considerations depend on species, contraceptives and contexts and involve trade-offs between reduced mortality and potential impacts on behaviour, physiology, and reproduction. Nevertheless, fertility control may offer welfare advantages over lethal methods and can reduce the transmission of infectious agents by maintaining social stability. Despite its potential, widespread implementation is constrained by economic and regulatory barriers. Overall, fertility control represents a valuable tool within integrated wildlife management strategies, though continued technological innovation and regulatory adaptation are essential for widespread application in the future.

Embryo implantation is a major reproductive bottleneck, requiring precise spatiotemporal coordination between the embryo and the maternal endometrium. This intricate communication is governed by synchronised molecular signalling, mechanical cues, and endocrine regulation. Although some of these mechanisms are conserved across mammals, marked species differences in the degree of invasiveness of implantation, decidualisation, and placental morphology, as well as in embryonic developmental milestones, limit comparative understanding of early pregnancy across species. Moreover, ethical restrictions on human embryo research, the need to reduce animal use in research, and the oversimplified nature of 2D cultures, which cannot replicate the 3D, multicellular organisation of the implantation site, have further constrained progress. Recent advances in 3D in vitro technologies, including organoids, blastoids, and biomaterial-based cultures, provide more physiologically relevant platforms for studying embryo-endometrium interactions. When integrated with organ-on-a-chip systems, these models enable dynamic control of hormonal gradients, paracrine signalling, and fluid flow, closely mimicking the native implantation microenvironment, unlike static cultures. These systems have yielded key insights into epithelial-stromal crosstalk, immune regulation, and vascular remodelling at the maternal-foetal interface. However, challenges remain regarding reproducibility and rigorous biological validation. This review explores the biological principles of implantation across mammalian species. It evaluates in vivo animal models and 2D and 3D in vitro models for their ability to recapitulate species-specific implantation strategies. Furthermore, we highlight how integrating cellular diversity, biomechanical forces, and species-specific tissue architecture into bioengineered 3D platforms, together with advanced imaging, can bridge the gap between in vitro approaches and complex in vivo physiology. The convergence of these technologies is poised to transform implantation research and ultimately improve reproductive outcomes.

Assisted reproductive technologies (ARTs) have been extensively developed in wild animal species over the last thirty years to become effective instruments for biodiversity conservation. These technologies, which were first adapted from advances in livestock species management and human medicine, have developed into more specialized methods suited to the particular anatomical and physiological traits of wild animal species. This article examines the development, improvement, and use of ARTs for animal conservation throughout a thirty-year period, emphasizing significant turning points, enduring difficulties, and potential future paths.

Reproductive performance of lactating dairy cows has improved largely over the past two decades. Such progress reflects advances in reproductive management practices, but also incorporation of fertility traits into genetic selection programs and improvements in cow comfort and health that have allowed high-producing dairy cows to better express their reproductive potential. This review summarizes recent developments in reproductive management strategies that have contributed to continued improvements in reproductive efficiency in lactating dairy cows. Increased availability of genomic data and automated monitoring technologies has created unique opportunities for the development of targeted management strategies tailored to specific cohorts of cows, which can reduce reproductive costs and allow for reorganization of routine tasks and labor utilization while maintaining reproductive performance. As the genetic makeup of high-producing dairy cows continues to evolve, understanding of the biological processes that control fertility will remain paramount so that novel technologies can be employed effectively as they become applicable to commercial farms. Strategies to improve reproductive performance of cows with inferior genetic merit for fertility and during the hot months of the year, among solutions to other physiological and environmental challenges, are expected to complement automated monitoring systems. Novel strategies for early identification and reinsemination of nonpregnant cows have allowed for the development of efficient resynchronization protocols.

Over the last two decades, reproductive research conducted primarily in Neotropical wildlife species from the Brazilian Caatinga has evolved from descriptive studies of reproductive biology into an integrated framework for biodiversity conservation. The trajectory described herein illustrates how basic reproductive physiology, when systematically linked to assisted reproductive technologies (ARTs), can generate practical conservation tools. Initial investigations focused on reproductive anatomy, endocrinology, spermatogenesis, follicular dynamics, and reproductive behavior. These studies provided the foundation for the development of species-specific methods for semen collection, sperm evaluation, estrous monitoring, hormonal manipulation, cryopreservation, in vitro culture, and xenotransplantation. Subsequent advances expanded conservation efforts from gamete preservation to gonadal tissue biobanking, ultimately supporting the establishment of integrated genetic resource conservation strategies. Using species from the Caatinga as experimental models, including collared peccaries, red-rumped agoutis, Spix's yellow-toothed cavies, six-banded armadillos, greater rheas, and other taxa, this research program generated knowledge applicable to a broad range of Neotropical wild species. Beyond summarizing scientific achievements, this article presents lessons learned during twenty years of research and discusses future opportunities involving advanced biobanking and the use of emerging assisted reproduction technologies. The experience demonstrates that long-term, species-centered programs can serve as effective pathways for transforming biological knowledge into conservation solutions.

In internally fertilizing animals, such as the pig, males transfer not only spermatozoa but also a complex mixture collectively termed seminal plasma (SP). SP contains diverse bioactive components, including proteins, peptides, cytokines, and various RNA species. Growing evidence indicates that SP contributes not only to the sperm quality but also modulates the female's immune responses. Major progress in biological knowledge and in the discovery of sperm quality biomarkers has been driven by advances in biotechnology and by the increasing affordability of omics technologies. With modern proteomic, (epi)genomic, transcriptomic, metabolomic, and functional analyses applied directly to semen, it is now possible to evaluate not only the functional state of the testes, epididymis, and accessory glands, but also to predict fertility through emerging biomarkers. Beyond diagnostics and fertility forecasting, new opportunities arise from the sperm quality biomarker definition using semen additives-such as specific molecules (proteins, peptides, enzymes) or extracellular vesicles (EVs). These EVs contain bioactive cargo protected within nanovesicles that can be isolated, stored, or even produced de novo in vitro. Boar spermatozoa are notoriously difficult to cryopreserve because they lose cholesterol during handling. EVs could fuse with sperm cells, deliver cholesterol‑rich lipids to the sperm membrane, and transfer specific proteins and nucleic acids. This raises the possibility that harvesting EVs, especially from highly fertile males, could be used in the future to improve sperm storage and even cryopreservation. Taken together, this review aims to list sperm fertility biomarkers that could be useful for the AI companies to discriminate sub-fertile males at an early stage.

The rapid expansion of in vitro embryo production (IVP) in cattle has established this technology as a major driver of genetic progress and production efficiency. Despite widespread adoption, IVP systems remain inherently inefficient, with substantial losses occurring from oocyte to blastocyst and variable outcomes following transfer. At the same time, significant advances in the understanding of oocyte competence and embryo biology have occurred. However, this knowledge has not consistently translated into improvements in commercial embryo production. The purpose of this review is to examine the gap between basic discovery and field application in bovine IVP and to define the biological and operational factors that limit successful translation at scale. A central constraint is the fundamental difference between systems optimized under controlled laboratory conditions and those required to perform consistently across diverse donor populations, laboratory environments, and high-throughput workflows. Biological variability, metabolic regulation, and the complexity of embryo physiology intersect with operational feasibility, including scalability, cost, and workforce constraints, to limit adoption of new approaches. A structured translational pipeline, from discovery through proof of concept, development, and implementation, is required to align mechanistic insight with commercial realities. Successful translation depends on integrating biological understanding with system robustness, evaluating outcomes beyond early developmental endpoints, and aligning research and industry priorities throughout the development process. Strengthening the collaboration between research and industry is essential for continued innovation and growth of bovine IVP systems.

Cryopreservation of bovine oocytes and in vitro produced (IVP) embryos represents a central tool for the global distribution of genetic material and the efficient application of assisted reproductive technologies. Although vitrification has become the preferred alternative to slow freezing because it avoids ice crystal formation, consistent and reproducible results are still difficult to achieve, especially in oocytes. Most vitrification protocols have traditionally been developed through empirical "trial and error" approaches, with limited consideration of the biological and biophysical factors that determine cryosurvival. Current progress, however, points toward a more rational framework based on membrane permeability, osmotic tolerance, cryoprotectant (CPA) toxicity, and mathematical modeling. This review provides a comprehensive evaluation of vitrification in bovine oocytes and IVP embryos by integrating biological, biophysical, and practical perspectives. It analyzes the cellular factors that limit cryotolerance and the advances in rational protocol design based on the quantitative analysis of membrane permeability and osmotic tolerance. The use of mathematical modeling, including temperature-dependent permeability data, has enabled the optimization of equilibration steps and reduced variability among laboratories. Moreover, strategies to mitigate cryodamage are discussed as promising but still inconsistent approaches. Technical improvements, including blastocoel collapse before vitrification and simplified warming systems for direct transfer, have also been evaluated for their potential to facilitate field application. Although vitrification remains biologically superior to slow freezing in terms of cryosurvival, its large‑scale implementation is limited by handling complexity and the lack of standardized direct‑transfer systems. Future progress in bovine cryopreservation will depend on combining enhanced cellular competence with biophysical optimization and standardized, reproducible procedures that can ensure not only improved post‑warming survival but also consistent pregnancy and calving outcomes in real production environments.

The acquisition of meiotic and developmental competence in oocytes is a highly regulated process that includes post-transcriptional mechanisms mediated by microRNAs (miRNAs). To characterize these changes, we compared mRNA and miRNA expression profiles between non-matured, and oocytes submitted to IVM in canines using RNA sequencing. The oocytes were obtained from antral follicles dissected from canine ovaries. Total RNA was isolated from pooled oocytes from each condition and subjected to parallel mRNA and miRNA sequencing, followed by differential expression and pathway enrichment analyses. Our findings reveal transcriptional change after in vitro culture, showing significant differential expression (FDR < 0.05, |log₂FC| > 1). Non-matured oocytes displayed an expression pattern associated with transcriptional preparation and structural organization, while IVM oocytes showed expression patterns consistent with cytoplasmic remodeling and metabolic activation. The miRNA profile changed with maturation, accompanied by a selective increase in miRNAs associated with post-transcriptional control of the cell cycle and structural pathways. Enrichment analysis revealed significant changes in signaling networks associated with cell adhesion, cytoskeletal organization, and communication. Components of the Hippo signaling pathway displayed altered transcript abundance following IVM, suggesting that structural and regulatory cues present within the oviduct may not be fully reproduced in culture. Our findings provide new insights into the molecular constraints of canine IVM that may serve as biomarkers for improving oocyte quality and reproductive technology outcomes in dogs.

Supplementary embryo transfer (ET) following artificial insemination (AI) is used in repeat-breeder cows; however, this dual-embryo approach inherently increases the risk of twin outcomes. This study evaluated whether transferring an embryo to the uterine horn contralateral to the corpus luteum (CL) could be associated with different calving outcomes from ipsilateral transfer. Holstein cows (n = 187; 79 nulliparous and 108 multiparous) received ipsilateral or contralateral ET 7-8 days after AI using frozen-thawed, in vitro-produced embryos. Repeat-breeder cows were clinically defined as cows failing to conceive after ≥3 artificial inseminations without evident reproductive abnormalities on routine examination. Data were analyzed using a generalized linear mixed model accounting for parity and technician. The calving rate was 34.8% (32/92) in the contralateral group and 46.3% (44/95) in the ipsilateral group, with no significant difference between groups (aOR = 0.62, 95% CI 0.33-1.15; P = 0.137). Twin calving incidence was numerically lower after contralateral ET (4.8%, 1/21) compared with ipsilateral ET (21.2%, 7/33; P = 0.131). Because this study was based on calving records and involved a limited number of animals, the findings should be interpreted cautiously. Contralateral supplementary ET may represent a practical option for further investigation.