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Assisted Reproduction Technologies To Improve Dairy Cattle Reproduction

机译：辅助繁殖技术以改善奶牛繁殖

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Over the past decades, dairy cattle reproduction has presented to farmers with several challenges as a consequence of genetic selection for improved milk production traits. These challenges include suboptimal postovulatory responses for timed artificial insemination synchronization protocols. Another example is the metabolic adjustments the preimplantation embryo may undergo in a high producing cow resulting in a high likelihood of early embryo loss. Nevertheless, this is an opportunity to study alternative options to improve pregnancy rates. Assisted Reproduction Technologies (ART) have the potential to solve several issues the modern dairy cow is facing. The progress in the practice of ART has been satisfactory over the last two decades and our understanding about gametes and embryo biology has substantially improved. Embryo transfers using in vitro produced embryos (IVP) might certainly have an advantage over conventional breeding methods since ovulation, fertilization and early embryonic stages would be bypassed thereby enhancing the likelihood of embryo implantation and hence improved conception rates. However, there are several challenges to producing good quality embryos in vitro due to difficulties in emulating the natural oviduct microenvironments that the preimplantation embryo is experiencing several physiological changes en route to the uterus. The objectives of this work were to review current literature in regard to mammalian preimplantation embryo production in vitro with emphasis in bovine species and to study the effect of metabolic regulators (MR) on embryo development as well as using new methods to recover better quality sperm especially when using sex-sorted semen. Chapter Two is an extensive review of the IVP process in mammalian species with emphasis on the bovine embryo. Metabolic processes during oocyte in vitro maturation, sperm interactions during fertilization and in vitro cultures of different preimplantation embryo stages are reviewed. Special attention was devoted to the metabolic switch from low to high glucose uptake and metabolism occurring at the morula stage. Chapter Three is a systematic study of the effects of conjugated linoleic acid (CLA) isomers on embryos produced in vitro. Inclusion of 100 [mu]M CLA- cis 9, trans 11 during embryo culture 36 hrs before cryopreservation resulted in embryos with higher survival and better developmental rates post-thaw when compared to other groups. Chapter Four presents a study about the effect of phenazine ethosulfate (PES) and 2, 4-dinitrophenol (DNP) on embryo development at the morula stage to enhance glucose uptake and metabolism to improve embryo developmental rates. Combination of 0.3 [mu]M PES and 10 [mu]M DNP resulted not only in higher embryo development and better quality but also embryos more resistant to cryopreservation procedures. Chapter Five describes a study of the effect of four colloidal-based sperm washes (Percoll, Old Bovipure, New Bovipure and Androcoll-B) on embryo development and quality. The International Embryo Transfer Society regulations strictly indicate that bovine embryos produced in vitro should be originated from sperm that has been recovered by silane-coated silica particles colloids when fractionation methods are used due to the debatable toxic effects of Percoll. Results from these experiments showed that embryos derived from sperm recovered by New Bovipure and Androcoll-B achieved higher blastocyst rates than Percoll and Old Bovipure groups. In addition, as a followup the effects of MR were evaluated on embryos originated from X-sorted semen. Interestingly, PES and DNP supplementation resulted in delayed development and poorer morphology in this embryos compared with untreated counterparts. Glucose uptake threshold may be lower in female embryos and/or they may have a different substrate preference as compared to male embryos. Our contribution to science may provide information for a better understanding of IVP and help shape the direction of future research. More importantly, it may provide the basis for production of better quality embryos originated from genderselected semen with more chance of survival to term, thereby improving conception rates in dairy cattle.
机译：在过去的几十年中，由于基因选择提高了牛奶生产性状，奶牛繁殖给农民带来了许多挑战。这些挑战包括定时人工授精同步协议的最佳排卵后反应。另一个例子是高产奶牛植入前胚胎可能经历的代谢调节，导致早期胚胎丧失的可能性很高。然而，这是一个研究替代方案以提高妊娠率的机会。辅助繁殖技术（ART）有潜力解决现代奶牛面临的几个问题。在过去的二十年中，抗逆转录病毒疗法的实践取得了令人满意的进展，我们对配子和胚胎生物学的了解已大大提高。使用体外产生的胚胎（IVP）进行胚胎移植肯定会比常规育种方法具有优势，因为将绕过排卵，受精和早期胚胎阶段，从而提高了胚胎植入的可能性，从而提高了受孕率。但是，由于难以模拟自然的输卵管微环境，即植入前的胚胎在进入子宫的过程中正在经历几种生理变化，因此在体外产生高质量的胚胎存在若干挑战。这项工作的目的是复习有关哺乳动物体外植入前胚胎生产的最新文献，重点是牛种，研究代谢调节剂（MR）对胚胎发育的影响，以及使用新方法来恢复质量更好的精子，特别是当使用按性别分类的精液时。第二章是对哺乳动物物种IVP过程的广泛回顾，重点是牛胚胎。综述了卵母细胞体外成熟过程中的代谢过程，受精过程中的精子相互作用以及不同植入前胚胎阶段的体外培养。特别注意的是在桑ula期发生的从低葡萄糖摄取到高葡萄糖的代谢转换和代谢。第三章系统研究了共轭亚油酸（CLA）异构体对体外产生的胚胎的影响。与其他组相比，在冷冻保存前36小时的胚胎培养过程中包含100μMCLA-cis 9，trans 11，导致胚胎在解冻后具有更高的存活率和更好的发育速率。第四章研究了吩嗪乙醇硫酸盐（PES）和2，4，4-二硝基苯酚（DNP）在桑ula期阶段对胚胎发育的影响，以增强葡萄糖的摄取和代谢，从而提高胚胎的发育速度。 0.3μMPES和10μMDNP的组合不仅导致更高的胚胎发育和更好的质量，而且导致对冷冻保存程序更有抵抗力的胚胎。第五章介绍了四种基于胶体的精子洗涤液（Percoll，Old Bovipure，New Bovipure和Androcoll-B）对胚胎发育和质量的影响的研究。国际胚胎移植学会的法规严格指出，体外分离产生的牛胚胎应源自精子，当使用分馏方法时，由于Percoll具有可争议的毒性作用，精子已被硅烷包覆的二氧化硅颗粒胶体回收。这些实验的结果表明，New Bovipure和Androcoll-B回收的精子胚胎的胚泡率高于Percoll和Old Bovipure组。另外，作为后续研究，对来自X分精液的胚胎的MR效果进行了评估。有趣的是，与未处理的对应物相比，补充PES和DNP导致该胚胎发育延迟和形态较差。雌性胚胎的葡萄糖摄取阈值可能较低，和/或与雄性胚胎相比，它们的底物偏好可能不同。我们对科学的贡献可为更好地理解IVP提供信息，并有助于塑造未来研究的方向。更重要的是，它可以为生产高质量的胚胎提供基础，这些胚胎来自性别选择的精液，有更多的生存期，从而提高了奶牛的受孕率。

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    Absalon-medina Victor;

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