Animal Reproduction最新文献

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.

This study evaluated two surgical sterilization techniques in free-ranging female capybaras (n = 21). The first group underwent uterine horn ligature (HL; n = 11), while the second was subjected to partial salpingectomy (S; n = 10). We assessed total operative time, incision length, the ease of identifying reproductive structures, the adequacy of exposure for surgical performance through flank or midline approaches, and the extent of abdominal viscera manipulation for each method. The HL method emerged as faster, with an average operative time difference of 16 minutes. In the S group, a flank mini-laparotomy over the ovarian topography facilitated easy exposure of the ipsilateral ovary and uterine tube, enabling ligature and partial resection of the uterine tube but not the uterine horn exposure. However, accessing the contralateral uterine tube without a bilateral incision was impractical, thus prolonging the total operative time due to the need for patient repositioning and new antisepsis procedures. Conversely, a post-umbilical approach for the HL method necessitated only one mini-laparotomy incision, offering ample uterine exposure for hysterotomy in pregnant females. Both methods involved minimal abdominal viscera manipulation and resulted in no fatalities or postoperative complications. Although direct comparison is limited by the distinct sterilization techniques and surgical approaches, this study underscores the challenges and surgical access of each method. Our findings endorse the HL technique as an effective contraception method for female capybaras to prevent the birth of seronegative offspring that could amplify Rickettsia sp., the causative agent of Brazilian spotted fever.

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.

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.

The aim of the study was to evaluate the use of Acustic Radiation Force Impulse (ARFI) elastography in mammary parenchyma and supramammary lymph nodes, for detection of active mastitis in sheep with naturally infected chronic fibrous lesions. 27 female sheep were included and B-mode ultrasound and ARFI elastography images were obtained, acquiring qualitative (echogenicity and echotexture) and quantitative (shear rate, depth and short/long axis ratio) variables of 48 mammary glands. The glands were divided into three experimental groups: control group (CG) - healthy animals; LSCC- animals that presented fibrous lesions and SCC (somatic cell count) less than 500 x 10³ cls/mL; HSCC: animals that presented fibrous lesions and SCC (somatic cell count) more than 500 x 10³ cls/mL; The qualitative variables using B-mode ultrasonography, including echotexture and echogenicity, showed no significant differences between the evaluated groups and tissues (p = 0.9336 and p = 0.233, respectively) .In healthy areas of the gland, it was an increasing in shear wave velocity (SWV) in LSCC than in HSCC (p=0.04). When comparing the fibrosis in the LSCC and HSCC groups with their respective normal areas, the velocity increased in both groups: LSCC (p= 0,0007) and HSCC (p= 0,0001). When comparing the areas of fibrosis in LSCC and HSCC with the CG parenchyma, there was an increase in LSCC (p=0.001) and HSCC (p=0.0001). B-mode ultrasound indicate predominance of hypoechoic echogenicity in lymph nodes and reduced short/long axis ratio in cases of active subclinical mastitis. The supramammary lymph node showed increased SWV when comparing the CG with HSCC groups (p=0.02) and GC with LSCC (p=0.04). B-mode ultrasonography is useful for evaluating the mammary parenchyma, however, its application as a standalone diagnostic technique is not recommended. ARFI elastography indicates potential cutoff points for differentiating subclinical mastitis from healed mastitis, highlighting its importance as a tool for distinguishing normal areas from fibrous parenchymal areas. While this study did not establish specific cutoff points due to sample size limitations, further research with larger sample sizes could explore and define these critical thresholds.

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.

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.

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.

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.

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.