Chicken spermatozoa are highly susceptible to cryopreservation often requiring extenders containing additives to enhance their post-thaw quality. Although protective properties of fetal bovine serum (FBS) during freezing of tissue cultured cells are widely known, its potential as a cryoprotectant for sperm cells has not been largely explored. Thus, the aims of our study were to (i) investigate the protective effect of FBS at different concentrations (0, 5, 10, 15 and 20%) against cryodamages in chicken spermatozoa, and (ii) test the FBS concentration that yielded the best preservation versus 1 mg/mL of cholesterol-loaded cyclodextrins (CLCs). Samples were assessed before and after freezing for sperm motility parameters, plasma membrane and acrosomal integrities, mitochondrial membrane potential, oxidative stress and plasma membrane peroxidation. Our findings showed that, despite their beneficial effects on fresh spermatozoa, higher FBS concentrations (15 and 20%) obtained the worst results for most motility and functional parameters after thawing. In contrast, lower FBS concentrations (5 and 10%) improved all post-thaw variables when compared to control. Afterwards, based on regression analysis, the concentration of 7% FBS was chosen to be assessed against CLCs in an experiment composed by four groups: control, FBS, CLCs, and FBS + CLCs. FBS and FBS + CLCs groups exhibited higher progressive motility in fresh samples, whereas only FBS maintained higher post-thaw progressive motility. Additionally, the incorporation FBS into extenders increased the percentage of rapid cells and reduced free radicals production and plasma membrane peroxidation. Together, these outcomes indicated that FBS minimize some harmful effects of cryopreservation, providing an alternative for chicken semen extenders that in many aspects appears to be superior to CLCs at 1 mg/mL.

中文翻译：

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胎牛血清对鸡精子体外冷冻存活的有益影响

鸡精子对冷冻保存非常敏感，通常需要含有添加剂的填充剂来提高其解冻后的质量。尽管胎牛血清 (FBS) 在组织培养细胞冷冻过程中的保护特性已广为人知，但其作为精子细胞冷冻保护剂的潜力尚未得到广泛探索。因此，我们研究的目的是 (i) 研究不同浓度 (0、5、10、15 和 20%) 的 FBS 对鸡精子冷冻损伤的保护作用，以及 (ii) 测试产生最佳保存与 1 mg/mL 胆固醇负载环糊精 (CLC)。在冷冻之前和之后评估样品的精子活力参数、质膜和顶体完整性、线粒体膜电位、氧化应激和质膜过氧化。我们的研究结果表明，尽管它们对新鲜精子有益，但较高的 FBS 浓度（15% 和 20%）在解冻后获得的大多数运动和功能参数的结果最差。相比之下，与对照相比，较低的 FBS 浓度（5% 和 10%）改善了所有解冻后变量。然后，基于回归分析，在由四组组成的实验中选择 7% FBS 的浓度来评估 CLC：对照、FBS、CLC 和 FBS + CLC。FBS 和 FBS + CLCs 组在新鲜样品中表现出更高的渐进运动，而只有 FBS 保持较高的解冻后渐进运动。此外，将 FBS 掺入增量剂可增加快速细胞的百分比并减少自由基的产生和质膜过氧化。一起，