Opportunities involving microfluidics and 3D culture systems to the in vitro embryo production

Traditional methods of gamete handling, fertilization, and embryo culture often face limitations in efficiency, consistency, and the ability to closely mimic in vivo conditions. This review explores the opportunities presented by microfluidic and 3D culture systems in overcoming these challenges and enhancing in vitro embryo production. We discuss the basic principles of microfluidics, emphasizing their inherent advantages such as precise control of fluid flow, reduced reagent consumption, and high-throughput capabilities. Furthermore, we delve into microfluidic devices designed for gamete manipulation, in vitro fertilization, and embryo culture, highlighting innovations such as droplet-based microfluidics and on-chip monitoring. Next, we explore the integration of 3D culture systems, including the use of biomimetic scaffolds and organ-on-a-chip platforms, with a particular focus on the oviduct-on-a-chip. Finally, we discuss the potential of these advanced systems to improve embryo production outcomes and advance our understanding of early embryo development. By leveraging the unique capabilities of microfluidics and 3D culture systems, we foresee significant advancements in the efficiency, effectiveness, and clinical success of in vitro embryo production.(AU)

Maternal contributions to pregnancy success: from gamete quality to uterine environment

The establishment and maintenance of a pregnancy that goes to term is sine qua non for the long-term sustainability of dairy and beef cattle operations. The oocyte plays a critical role in providing the factors necessary for preimplantation embryonic development. Furthermore, the female, or maternal, environment where oocytes and embryos develop is crucial for the establishment and maintenance of a pregnancy to term. During folliculogenesis, the oocyte must sequentially acquire meiotic and developmental competence, which are the results of a series of molecular events preparing the highly specialized gamete to return to totipotency after fertilization. Given that folliculogenesis is a lengthy process in the cow, the occurrence of disease, metabolic imbalances, heat stress, or other adverse events can make it challenging to maintain oocyte quality. Following fertilization, the newly formed embryo must execute a tightly planned program that includes global DNA remodeling, activation of the embryonic genome, and cell fate decisions to form a blastocyst within a few days and cell divisions. The increasing use of assisted reproductive technologies creates an additional layer of complexity to ensure the highest oocyte and embryo quality given that in vitro systems do not faithfully recreate the physiological maternal environment. In this review, we discuss cellular and molecular factors and events known to be crucial for proper oocyte development and maturation, as well as adverse events that may negatively affect the oocyte; and the importance of the uterine environment, including signaling proteins in the maternal-embryonic interactions that ensure proper embryo development. We also discuss the impact of assisted reproductive technologies in oocyte and embryo quality and developmental potential, and considerations when looking into the prospects for developing systems that allow for in vitro gametogenesis as a tool for assisted reproduction in cattle.(AU)

The interaction between the environment and embryo development in assisted reproduction

It can be assumed that the natural processes of selection and developmental condition in the animal provide the best prerequisites for embryogenesis resulting in pregnancy and subsequent birth of a healthy neonate. In contrast, circumventing the natural selection mechanisms and all developmental conditions in a healthy animal harbors the risk of counteracting, preventing or reducing the formation of embryos or substantially restricting their genesis. Considering these facts, it seems to be obvious that assisted reproductive techniques focusing on early embryonic stages serve an expanded and unselected germ cell pool of oocytes and sperm cells, and include the culture of embryos outside their natural habitat during and after fertilization for manipulation and diagnostic purposes, and for storage. A significant influence on the early embryonic development is seen in the extracorporeal culture of bovine embryos (in vitro) or stress on the animal organism (in vivo). The in vitro production per se and metabolic as well as endocrine changes in the natural environment of embryos represent adequate models and serve for a better understanding. The purpose of this review is to give a brief presentation of recent techniques aimed at focusing more on the complex processes in the Fallopian tube to contrast in vivo and in vitro prerequisites and abnormalities in early embryonic development and serve to identify potential new ways to make the use of ARTs more feasible.(AU)

In vivo embryo development in bitches inseminated laparoscopically after ovulation time estimated based on a single progesterone determination

Logistic and economical limitations are often the causes of dog owners not accurately monitoring the estrous cycle and the optimal insemination time. The aim of this study was to evaluate in vivo early embryonic development in bitches, after the analysis of sequential vaginal cytologies associated to single progesterone measurement and single laparoscopic insemination with high quality semen (fresh and with high spermatozoa concentration) or low-quality semen (frozen/thawed and with low spermatozoa concentration) at 48 h post- ovulation time predicted on a single progesterone measurement. Ten bitches were inseminated with 250 x 106 fresh spermatozoa (80% motility), and ten with 80 x 106 frozen/thawed spermatozoa (60% motility) in the cranial part of each uterine horn. Seven days later, ovariohysterectomy was performed and the oviducts and uterine horns and body were flushed to recover embryos and unfertilized oocytes. In 80% of the bitches inseminated with fresh and 50% of bitches inseminated with frozen/thawed semen, embryos at 2 to 8 cells stage were recovered mostly from the, oviducts. This study indicates that pregnancies can be obtained with a single laparoscopic intrauterine insemination after single serum progesterone measurement, although with a low number of embryos. This result should be taken into account in case economic or logistic restrictions that affect the possibility of owners to plan an accurate monitoring of the optimal breeding time using fresh and frozen semen.(AU)

The impact of microplastics on female reproduction and early life

Plastic pollution in our environment is one of the most important global health concerns right now. Micro- and nanoplastics (MNPs) are taken up by both humans and animals, mainly via food and water, and can pass important epithelial barriers. Indications of plastics in the blood circulation have recently been shown in both humans and farm animals, but standardized methods to quantify the exact levels of MNPs to which we are exposed are currently lacking. Potential hazards of MNPs are being investigated very recently, including the impact that MNPs may have on reproduction. However, studies on mammalian reproduction are scarce, but a wealth of data from aquatic species indicates reproductive effects of MNPs. The first studies in rodent models demonstrate that MNPs reach the gonads after oral exposure and may impact offspring after maternal exposure during the gestational period. These effects may arise from the particles themselves or the presence of plastic contaminants that leach from plastics. Plastic contamination has been detected in human placentas, fetal fluid and the meconium of newborns, indicating the presence of plastics from the very first start of life. Currently there is a lack of studies that investigate the impact of MNP exposure during the periconception and embryonic period, whereas this is an extremely sensitive period that needs considerable attention with the growing amount of plastics in our environment.(AU)

Interação da sazonalidade e nutrição na viabilidade embrionária ovina / Interaction between seasonality and nutrition on embrio viability of ovines

A sazonalidade reprodutiva e a condição nutricional são os principais fatores que influenciam o desempenho reprodutivo em ovinos, principalmente em áreas onde a disponibilidade de alimentos é altamente sazonal. A desnutrição pode comprometer a competência folículo-oocitária, a função lútea e o desenvolvimento embrionário. Por outro lado, o tratamento com melatonina é um método eficaz para induzir ciclicidade, aumentando a ovulação e melhorando a viabilidade do embrião durante o anestro. Portanto, levantamos a hipótese de que a melatonina pode substituir os efeitos prejudiciais da desnutrição para melhorar o desempenho reprodutivo em ovelhas. A este respeito, esta revisão enfoca os efeitos da interação entre melatonina e nutrição na viabilidade do embrião e resume a informação disponível sobre o efeito da melatonina exógena na viabilidade do embrião em ovelhas desnutridas.(AU)

Reproductive seasonality and nutritional condition are the main factors that influence reproductive performance in sheep, particularly in the areas where the availability of food is highly seasonal. Undernutrition can compromise follicle-oocyte competence, luteal function and embryo development. On the other hand, melatonin treatment is an effective method for inducing estrous cycles, increasing ovulation and improving embryo viability during anestrus. Therefore, we hypothesized that melatonin can override the detrimental effects of undernutrition to improve reproductive performance in ewes. In this regard, this review focuses on the effects of the interaction between melatonin and nutrition on embryo viability and summarizes the available information about the effect of exogenous melatonin on embryo viability in undernourished ewes.(au)

In vitro germination and reserve mobilization of Vriesea friburgensis Mez / Germinação in vitro e mobilização de reservas de Vriesea friburgensis Mez

Studies on the germination and establishment of plants are key pieces to understanding the reproductive success of plants. This work aimed to describe in vitro germination and reserve mobilization in the bromeliad Vriesea friburgensis through morphological, histochemical, and biochemical analysis. The conditions used in this study for the in vitro germination are adequate. From the third day of in vitro inoculation, a uniform germination of 98% was obtained, exhibiting a high physiological quality of the seeds and a high potential to produce seedlings (94%). There is early reserve mobilization, which began in the imbibition phase. The accumulated reserves in the endosperm cytoplasm are degraded by hydrolytic enzymes provided by the aleurone layer. It is possible that compounds in the cell walls of the endosperm contribute to a lesser extent in mobilization. Additionally, it was observed that starch accumulation in the cotyledon increases when the seedling has formed. Results from this study provide insights for future studies on ecology, seed technology, and conservation in this species. This study contributes to the limited knowledge of the dynamics of reserves during germination and seedling establishment in Bromeliaceae. To the best of our knowledge, this is the first study with this approach in the genus Vriesea.

Estudos sobre germinação e estabelecimento de plantas são peças-chave para entender o sucesso reprodutivo das plantas. Este trabalho teve como objetivo descrever a germinação in vitro e a mobilização de reservas na bromélia Vriesea friburgensis por meio de análises morfológicas, histoquímicas e bioquímicas. As condições utilizadas neste estudo para a germinação in vitro são adequadas. A partir do terceiro dia de inoculação in vitro, obteve-se germinação uniforme de 98%, apresentando alta qualidade fisiológica das sementes e alto potencial de produção de plântulas (94%). Há uma mobilização precoce de reservas, iniciada na fase de embebição. As reservas acumuladas no citoplasma do endosperma são degradadas por enzimas hidrolíticas fornecidas pela camada de aleurona. É possível que compostos nas paredes celulares do endosperma contribuam em menor grau na mobilização. Além disso, observou-se que o acúmulo de amido no cotilédone aumenta com a formação da plântula. Os resultados deste estudo fornecem informações para estudos futuros sobre ecologia, tecnologia de sementes e conservação desta espécie. Este estudo contribui para o conhecimento limitado da dinâmica das reservas durante a germinação e estabelecimento de plântulas em Bromeliaceae. Até onde sabemos, este é o primeiro estudo com esta abordagem no gênero Vriesea.

Embryo biopsies for genomic selection in tropical dairy cattle

Genomic selection has transformed the livestock industry, enabling early-life selection of animals. Biopsy sampling of pre-implantation embryos has been described since 1968. However, it was only after 2010, with the advancement of molecular biology techniques such as whole genomic amplification and SNP Chips, that next-generation sequencing became commercially available for bovine embryos. It is now possible to make decisions about which embryos to transfer not only based on recipients' availability or embryo morphology but also on genomic estimates. This technology can be implemented for a wide spectrum of applications in livestock. In this review, we discuss the use of embryo biopsy for genomic selection and share our experience with Gir and Girolando Brazilian breeding programs, as well as future goals for implementing it in Brazilian bovine in vitro embryo production practices.(AU)

Efeitos da melatonina exógena na viabilidade embrionária e no ambiente uterino de ovelhas / Effects of exogenous melatonin on embryo viability and uterine environment of ewes

O objetivo deste artigo é revisar o efeito da melatonina na viabilidade embrionária e ambiente uterino em ovinos, tanto in vivo quanto in vitro, considerando as vias pelas quais esse hormônio pode ter influência no embrião ou o mecanismo de reconhecimento materno e estabelecimento de gravidez em ovelhas.(AU)

The aim of this article is to review the effect of melatonin on embryo viability and uterine environment in sheep, both in vivo and in vitro, considering the pathways by which this hormone could have influences at the embryo or the mechanism of maternal recognition and establishment of pregnancy in sheep.(AU)

The embryo non-invasive pre-implantation diagnosis era: how far are we?

Advancements in assisted reproduction (AR) methodologies have allowed significant improvements in live birth rates of women who otherwise would not be able to conceive. One of the tools that allowed this improvement is the possibility of embryo selection based on genetic status, performed via preimplantation genetic testing (PGT). Even though the widespread use of PGT from TE biopsy helped to decrease the interval from the beginning of the AR intervention to pregnancy, especially in older patients, in AR, there are still many concerns about the application of this invasive methodology in all cycles. Therefore, recently, researchers started to study the use of cell free DNA (cfDNA) released by the blastocyst in its culture medium to perform PGT, in a method called non-invasive PGT (niPGT). The development of a niPGT would bring the diagnostics power of conventional PGT, but with the advantage of being potentially less harmful to the embryo. Its implementation in clinical practice, however, is under heavy discussion since there are many unknowns about the technique, such as the origin of the cfDNA or if this genetic material is a true representative of the actual ploidy status of the embryo. Available data indicates that there is high correspondence between results observed in TE biopsies and the ones observed from cfDNA, but these results are still contradictory and highly debatable. In the present review, the advantages and disadvantages of niPGT are presented and discussed in relation to tradition TE biopsy-based PGT. Furthermore, there are also presented some other possible non-invasive tools that could be applied in the selection of the best embryo, such as quantification of other molecules as quality biomarkers, or the use artificial intelligence (AI) to identify the best embryos based on morphological and/or morphokitetic parameters.(AU)

Pontos críticos na produção de embriões equinos com enfoque na doadora / Critical points in the production of equine embryos with a donor approach

Inúmeras são as vantagens da utilização da técnica de transferência de embriões (TE) em equinos. No entanto, alguns fatores podem afetar a taxa de recuperação embrionária: dia da colheita do embrião; condição uterina e idade da doadora; manejos reprodutivo, sanitário e nutricional; garanhão/qualidade do sêmen; habilidade do técnico; condições climáticas, número de ovulações e adaptação da doadora. O objetivo deste artigo é revisar os fatores que podem exercer influência sobre a taxa de recuperação embrionária tendo impacto direto nos índices reprodutivos de um programa de TE.(AU)

There are countless advantages of using the embryo transfer (ET) technique in horses. However, some factors may affect the embryonic recovery rate: day of embryo collection; uterine condition and donor age; reproductive, health and nutritional management; stallion/semen quality; skill of the technician; climatic conditions, number of ovulations and adaptation of the donor. The objective of this article is to review those factors that can influence the embryonic recovery rate, having a direct impact on the reproductive rates of an ET program.(AU)

Processos que afetam a taxa de gestação pós-inovulação do embrião equino / Processes that affect pregnancy rate after embryo transfer

A transferência de embriões equinos é uma biotecnologia que traz inúmeros benefícios reprodutivos para um haras. Entretanto, os índices reprodutivos obtidos numa estação de monta podem ser afetados por diversos fatores que interferem tanto na recuperação embrionária que normalmente são relacionados à doadora de embriões, quanto na taxa de gestação na receptora de embriões. O objetivo do presente artigo foi revisar os fatores relacionados à receptora de embriões em programas de transferência de embriões equinos.(AU)

Equine embryo transfer is a biotechnology that brings reproductive benefits to a stud farm. However, the reproductive rates obtained in a breeding season can be affected by several factors that interfere both in the embryonic recovery that are normally related to the embryo donor, and in the pregnancy rate in the embryo recipient. The aim of this article was to review the factors related to the recipient of embryos in equine embryo transfer programs.(AU)

Estudos para o incremento da produção de embriões in vivo e in vitro em vacas de corte taurinas e sintéticas / Studies to improve in vivo and in vitro embryo production in beef cows from taurine and synthetic breeds

O Brasil destaca-se por ser um dos líderes mundiais na produção in vitro de embriões, o que é decorrente do rebanho nacional ser predominantemente composto por raças zebuínas, que possuem maior número de folículos antrais aspiráveis. Por outro lado, vacas taurinas apresentam menor população folicular antral, o que limita o número de ovócitos obtidos por seção de aspiração folicular (ovum pick-up; OPU). Portanto, na região Sul do Brasil há demanda para produção tanto in vivo como in vitro de embriões de doadoras de raças taurinas e sintéticas. Este texto discute estudos recentes que buscam estratégias para aperfeiçoar as etapas envolvidas na produção de embriões bovinos, bem como para aumentar o aproveitamento de receptoras utilizadas nos programas de transferência de embriões (TE), com foco em vacas taurinas e sintéticas.(AU)

Brazil stands among the leaders on in vitro embryo production, as the Brazilian herd is predominantly composed by Zebu breeds, which have a greater number of antral follicles available to ovum pick-up (OPU). On the other hand, taurine cows have a lower antral follicle population, which limits the number of oocytes obtained by each OPU section. Therefore, in the Brazilian Southern region there is a demand for both in vivo and in vitro production of embryos from donors of taurine and synthetic breeds. This text discusses recent studies that seek strategies to improve the steps involved in the production of bovine embryos, as well as to increase the use of recipients in embryo transfer (ET) programs, focusing on taurine and synthetic cows.(AU)

Prostaglandin F2α treatment concurrent with artificial insemination does not affect bovine embryo production / Administração de prostaglandina F2 alfa no momento da inseminação artificial não afeta a produção de embriões bovinos

ABSTRACT: Treatment with prostaglandin F2α (PGF) induces ovulation and increases conception rates in cows, while improving embryo production in buffalos. However, its effect on superovulated cows is unknown. This study verified whether single PGF administration concurrent with artificial insemination (AI) improves fertilization and embryo production rates in superovulated cows. In each replicate, embryo donor cows were equally allocated to two groups: the untreated control and PGF groups. The latter of which received 482 µg of cloprostenol concurrent with the first AI. Each cow (n = 35) was subjected to two superovulations (SOV) in a crossover design (total = 70 embryo collections). In the control and PGF groups, respectively, the observed responses were [median (95% CI)]: 12 (10-18) and 15 (12-18) total structures, 9 (7-11) and 7 (6-10) viable embryos, 1 (0-1) and 1 (1-3) degenerated embryos, and 1 (0-3) and 2 (0-5) oocytes (P > 0.05). In conclusion, single PGF treatment concurrent with the first AI did not affect embryo production in superovulated cows.

RESUMO: A prostaglandina F2α (PGF) pode induzir a ovulação e melhorar tanto a concepção em vacas, como a produção de embriões em búfalas, mas o efeito em vacas superovuladas é desconhecido. Esse estudo teve como objetivo verificar se a administração de uma dose de PGF na inseminação artificial (IA) após a superovulação (SOV) melhora as taxas de fecundação e produção embrionária em vacas. Em cada replicação, vacas doadoras de embriões foram equilibradamente alocadas em dois grupos: controle, não tratado, ou PGF, que recebeu 482 µg de cloprostenol no momento da primeira IA. Cada doadora (n = 35) foi submetida a duas SOV em um delineamento crossover (total = 70 coletas de embriões). Nos grupos controle e PGF, respectivamente, foram observados [medianas (IC 95%)]: 12 (10-18) e 15 (12-18) estruturas totais; 9 (7-11) e 7 (6-10) embriões viáveis; 1 (0-1) e 1 (1-3) embriões degenerados; e 1 (0-3) e 2 (0-5) ovócitos (P > 0,05). Conclui-se que uma única administração de PGF no momento da primeira IA não afeta a produção embrionária de vacas superovuladas.

Prostaglandin F2α treatment concurrent with artificial insemination does not affect bovine embryo production / Administração de prostaglandina F2 alfa no momento da inseminação artificial não afeta a produção de embriões bovinos

Treatment with prostaglandin F2α (PGF) induces ovulation and increases conception rates in cows, while improving embryo production in buffalos. However, its effect on superovulated cows is unknown. This study verified whether single PGF administration concurrent with artificial insemination (AI) improves fertilization and embryo production rates in superovulated cows. In each replicate, embryo donor cows were equally allocated to two groups: the untreated control and PGF groups. The latter of which received 482 µg of cloprostenol concurrent with the first AI. Each cow (n = 35) was subjected to two superovulations (SOV) in a crossover design (total = 70 embryo collections). In the control and PGF groups, respectively, the observed responses were [median (95% CI)]: 12 (10-18) and 15 (12-18) total structures, 9 (7-11) and 7 (6-10) viable embryos, 1 (0-1) and 1 (1-3) degenerated embryos, and 1 (0-3) and 2 (0-5) oocytes (P > 0.05). In conclusion, single PGF treatment concurrent with the first AI did not affect embryo production in superovulated cows.

A prostaglandina F2α (PGF) pode induzir a ovulação e melhorar tanto a concepção em vacas, como a produção de embriões em búfalas, mas o efeito em vacas superovuladas é desconhecido. Esse estudo teve como objetivo verificar se a administração de uma dose de PGF na inseminação artificial (IA) após a superovulação (SOV) melhora as taxas de fecundação e produção embrionária em vacas. Em cada replicação, vacas doadoras de embriões foram equilibradamente alocadas em dois grupos: controle, não tratado, ou PGF, que recebeu 482 µg de cloprostenol no momento da primeira IA. Cada doadora (n = 35) foi submetida a duas SOV em um delineamento crossover (total = 70 coletas de embriões). Nos grupos controle e PGF, respectivamente, foram observados [medianas (IC 95%)]: 12 (10-18) e 15 (12-18) estruturas totais; 9 (7-11) e 7 (6-10) embriões viáveis; 1 (0-1) e 1 (1-3) embriões degenerados; e 1 (0-3) e 2 (0-5) ovócitos (P > 0,05). Conclui-se que uma única administração de PGF no momento da primeira IA não afeta a produção embrionária de vacas superovuladas.

Taxa de recuperação embrionária em éguas Mangalarga Marchador inseminadas com sêmen refrigerado / Embryonic recovery rate in Mangalarga Marchador mares inseminated with refrigerated semen

O acompanhamento reprodutivo da espécie equina tem sido cada vez mais aplicado na aplicade de diversos países, resultando em melhores índices reprodutivos para a espécie e em animais de linhagens selecionadas. Nos programas de transferência de embrião, a taxa de recuperação embrionária consiste em um parâmetro essencial a fim de verificar o sucesso da técnica. Por conseguinte, este trabalho propõe-se a avaliar as taxas de recuperação embrionária de éguas doadoras submetidas à inseminação artificial com sêmen refrigerado de maneira a complementar os dados relacionados ao assunto. Conforme os dados coletados durante a estação de monta de agosto de 2018 a fevereiro de 2019, obteve-se 129 lavados uterinos provenientes de 20 éguas e 83 embriões recuperados. Desse modo, a taxa de recuperação embrionária obtida foi de 64,34%. Diante dos dados apresentados neste estudo, conclui-se que a aplicabilidade da técnica de recuperação embrionária visando o uso do sêmen refrigerado na inseminação artificial de éguas se mostra promissora, pois permite o transporte de material genético de alto valor entre propriedades sem interferir drasticamente nos índices dos programas de reprodução.

The reproductive monitoring of the equine species has been increasingly applied in several countries, resulting in better reproductive rates for the species and in animals from selected strains. In embryo transfer programs, the embryo recovery rate is an essential parameter to verify the technique success. Therefore, the present work proposes to evaluate the embryo recovery rates of donor mares submitted to artificial insemination with refrigerated semen to complement the data related to the subject. According to the data collected during the breeding season for the period from August 2018 to February 2019, 129 uterine washes were obtained from 20 mares and 83 recovered embryos. Thus, the embryonic recovery rate obtained was 64.34%. Given the data presented in this study, it is concluded that the applicability of the embryonic recovery technique aiming at the use of refrigerated semen in artificial insemination of mares is promising, as it allows the transport of high-value genetic material between properties without interfering dramatically in breeding program indexes.

Bem-estar animal nos procedimentos de produção in vivo de embriões na espécie ovina / Animal welfare in the in vivo production of sheep embryos

A presente revisão tem por objetivo abordar aspectos relacionados ao bem-estar animal na produção in vivo de embriões ovinos. A cobrança da sociedade tem impulsionado o uso de práticas que atendam os preceitos de bem-estar na produção animal. Nesse contexto, destaca-se a necessidade de aprimoramento de procedimentos menos invasivos, como a coleta não cirúrgica de embriões. Avanços recentes nos protocolos de dilatação cervical melhoraram os resultados e tornaram essa técnica uma alternativa viável na espécie ovina. No entanto, a avaliação do estado de bem-estar das doadoras submetidas à coleta transcervical mostra a necessidade de melhor controle da dor durante a sua realização. Assim, acreditamos que a associação dos esforços de diferentes pesquisas pode proporcionar a resolução desses entraves e possibilitar maior aplicabilidade comercial da biotécnica.(AU)

This review aims to address aspects related to animal welfare in the in vivo production of ovine embryos. The use of practices that meet the precepts of welfare in animal production has been driven by demands from society. In this context, there is a need to improve less invasive procedures, such as nonsurgical embryo collection. Recent advances in cervical dilation protocols have improved results and made this technique a viable alternative in sheep. However, the assessment of the state of welfare of donors undergoing transcervical collection shows the need for better pain control during its performance. Thus, the association of different research efforts can provide the resolution of these obstacles and enable greater commercial applicability of the biotechnique.(AU)

The waveless model: clinical and research applications of follicular wave suppression in cattle / Modelo waveless: aplicações clínicas e na pesquisa da supressão das ondas foliculares em bovinos

The follicular growth waves are directly linked to the fluctuations in plasma gonadotrophins, which are controlled by the hypothalamic GnRH release pattern. Therefore, if the actions of the GnRH are inhibited or blocked, the final stages of the antral follicle growth are suppressed, resulting in an induced anestrus (a.k.a. waveless model). In the human medicine, GnRH agonists or antagonists are broadly used in the control of ovarian disfunctions, as well as in the preparation of women for assisted reproductive cycles. In cattle, a similar effect can be obtained by active immunization against GnRH. This was shown to be a viable strategy, for example, for the control of chronic cases of cystic ovarian disease in oocyte donors. However, on shall take into account the substantial individual variation on the immune response and, consequently, the lack of control of the duration of the anestrus induced. The waveless model is also very useful as a research model, once it controls the potential interference of the endogenous FSH and LH, improving the sensitivity of essays with exogenous hormones and consequently reducing the required number of replicas within studies.(AU)

O padrão de crescimento folicular em ondas está diretamente associado às flutuações nas concentrações plasmáticas de gonadotrofinas, controladas por sua vez pelo padrão de liberação de GnRH hipotalâmico. Desta forma, a inibição ou bloqueio da ação do GnRH suprime as etapas finais do crescimento folicular, resultando em anestro induzido (também chamado modelo waveless). Na medicina humana, agonistas ou antagonistas de GnRH são utilizados tanto no controle de disfunções ovarianas quanto na preparação de pacientes para procedimentos de reprodução assistida. Em bovinos, este efeito pode ser obtido pela imunização ativa contra GnRH, e mostrou-se estratégia viável, por exemplo, no controle de casos crônicos de doença ovariana cística em doadoras de oócitos. Contudo, é importante considerar a grande variação individual na resposta à imunização e consequente impossibilidade de controlar a duração do anestro induzido. O modelo waveless também é de grande utilidade na pesquisa, uma vez que elimina a potencial interferência do FSH e LH endógenos, aumentando a sensibilidade nos ensaios com hormônios exógenos e consequentemente reduzindo o número de réplicas necessárias nos estudos.(AU)

Growth performance, reproductive parameters and fertility measures in young Nellore bulls with divergent feed efficiency

The growth, sexual maturity and fertility-related parameters related of young Nellore bulls with divergent residual feed intake (RFI) raised on pasture were evaluated. After classification of 48 young males as low and high RFI (more and less efficient, respectively), the animals were evaluated for growth and reproductive parameters at 28-day intervals from 14.3 to 24.6 months of age. The semen was cryopreserved in the last sampling and fresh and post-thaw semen samples were evaluated. Low RFI bulls exhibited higher initial and final body weight (P < 0.05), but feed intake, body condition score and growth measures evaluated by carcass ultrasound were unaffected by RFI (P > 0.05). The scrotal circumference, sperm concentration, defects, and quality of fresh semen, and ultrasonographic testicular characteristics were unaffected by RFI (P > 0.05). However, velocity parameters such as average path and curvilinear velocities determined by computer-assisted sperm analysis of thawed semen submitted to the rapid thermoresistance test were improved (P < 0.05) in low RFI bulls, but this improvement in quality did not enhance in vitro sperm fertilizing ability. Our results demonstrated significant differences in metabolism and growth performance between bulls of divergent RFI. In addition, there was slight improvement in the semen quality of bulls with low RFI bulls, but this did not enhance in vitro fertilizing ability. Selection of beef bulls for RFI can be performed, which will result in economic benefits by improving the growth performance of the animals without affecting reproductive parameters.(AU)

Endometrial receptivity in cattle: the mutual reprogramming paradigm

Prior to implantation in cattle, the mucous medium contained in the uterine lumen serves as a working interface for molecular exchange and signaling between the lining endometrium and the embryo. The composition of this luminal fluid changes temporally according to the secretory and reabsorptive activities of the uterus and the embryo, which are under complex regulation. Via this interface, both the embryo and the endometrium reprogram each other's functions to support pregnancy continuation beyond the pre-implantation period. More specifically, the embryo receives elongation signals and the uterus receives anti-luteolytic stimuli. Here, characteristics of the luminal compartment as well as the regulation of its composition to determine the pregnancy outcome will be discussed.(AU)