Canine semen cryoconservation was used since 1969, and this process is still nowadays in progress. This review aims to have an overview of two factors leading to a successful freezing-thawing semen. The success and efficiency of freezing process can be measured by the post-thawing sperm mobility. The first factor is the best extender used as a cryoprotectant to have a similar osmolarity and pH compared to the seminal plasma to enable sperm survival. Historically, chicken egg yolk was used since 1940, but due to microbial risks and to the presence of granules (which interfere with counting dead spermatozoa and inhibits a spermatozoal respiration), despite these disadvantages, egg yolk is considered an excellent cryoprotectant for sperm of different animal species. The low-density lipoproteins (LDL), contained in EY, when used at a concentration of 6% in a freezing medium associated with 20 mM of glutamine, show a mobility up to 54.5%, which is the best combination found. However, the sperm protection mechanism by LDL during freezing-thawing process only begins to be decrypted. But extraction protocols of LDL are not efficient for an industrial use. Therefore, egg yolk plasma is used within liquid or lyophilized state, and offering similar efficiency as the 6% LDL middle. The equilibration step, in which the diluted sperm is placed for a variable period of time at a temperature of +4°C, before freezing it. The studies show that 6 hr is the optimal duration for the canine sperm equilibration. The future of canine sperm cryopreservation is expected in liposome use and synthetic substances, which mimics LDL role.

中文翻译：

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犬精液冷冻保存：最近20年的新数据。

自1969年开始使用犬精液冷冻保存，如今这一过程仍在进行中。这篇综述旨在概述导致精液成功解冻的两个因素。冷冻过程的成功和效率可以通过解冻后的精子活动性来衡量。第一个因素是用作冷冻保护剂的最佳填充剂，与精浆相比具有相同的渗透压和pH值，可以使精子存活。从历史上看，蛋黄自1940年以来就被使用，但是由于存在微生物风险和存在颗粒（干扰计数死精子并抑制精子呼吸），尽管存在这些缺点，蛋黄仍被认为是不同精子的极佳冷冻保护剂动物种类。安永所包含的低密度脂蛋白（LDL）当在与20 mM谷氨酰胺相关的冷冻培养基中以6％的浓度使用时，显示出高达54.5％的迁移率，这是发现的最佳组合。但是，在解冻过程中，LDL的精子保护机制才开始被解密。但是，LDL的提取协议对于工业用途而言效率不高。因此，蛋黄血浆可在液态或冻干状态下使用，并提供与6％LDL中值相似的效率。平衡步骤，在冷冻之前，将稀释的精子在+ 4°C的温度下放置可变的时间。研究表明，6小时是犬精子平衡的最佳持续时间。犬精子冷冻保存的未来有望用于脂质体和模拟LDL作用的合成物质。