Centro de Investigación y Tecnología Agroalimentaria de Aragón, Zaragoza, Spain.
Theriogenology. 2011 Jul 1;76(1):97-109. doi: 10.1016/j.theriogenology.2011.01.022. Epub 2011 Mar 11.
It is widely accepted that sperm morphology is a good indicator of fertility and it has been proposed that sperm quality may be related to subtle changes in sperm head morphology. However, a precise estimation of the morphology of ram sperm would be very useful to improve reproductive success in ovine. Computer-assisted morphometric analysis and clustering analysis have been important tools to study sperm subpopulations in domestic animals. However, to the best of our knowledge, no data exist studing morphometric differences regarding to sperm subpopulations within the ovine ejaculate. The aim of this study was to test the presence and distribution of sperm morphometric subpopulations in cryopreserved ejaculates from yearling and mature rams using an objective method by computer analysis system and to establish the relationship between the distribution of the subpopulations found and sperm quality in each individual ram. Principal component analysis revealed that three principal components for yearlings and four components for mature rams that represented more than 84% of the cumulative variance in both cases. After cluster analysis, three sperm morphometric subpopulations for yearlings (CLY) and four for mature (CLM) rams were identified with defined sperm dimensions and shapes. CLY1 included big, round and short sperm (37%), CLY2 included average size and slightly elliptical and elongated sperm (48%), CLY3 included small, long, elliptical and elongated sperm cells (15%). CLM1 consisted of average size and moderate elliptical and elongated (26%), CLM2 consisted of small, long, elliptical and elongated (31%), CLM3 consisted of small and round (32%) and CLM4 included big, short and round (8%) spermatozoa respectively. There were significant differences in the distribution of the three subpopulations (P < 0.001) as well as in the sperm concentration, total motility (%), sperm viability (%) and the overall (P < 0.05) in the ejaculates among the four yearling rams tested. Same results were found for the four subpopulations and the different sperm quality parameters in the ejaculates among the four mature rams tested. In conclusion, cryopreserved ram semen showed a specific structure with regard to sperm morphometric subpopulations. In addition, the distribution of these subpopulations seems to be related to stud maturity age and the ejaculate quality which would be a very important indicator of sperm function. Thus, analysis of sperm morphometric subpopulation structure together with functional tests could provide valuable information to assess the cryoresistence of ram spermatozoa.
人们普遍认为精子形态是生育能力的一个良好指标，并且有人提出精子质量可能与精子头部形态的细微变化有关。然而，对绵羊精子形态进行精确估计将非常有助于提高绵羊的繁殖成功率。计算机辅助形态计量分析和聚类分析已成为研究家畜精子亚群的重要工具。然而，据我们所知，目前还没有关于绵羊精液中精子亚群形态计量差异的研究数据。本研究旨在使用计算机分析系统的客观方法，检测青年和成年公羊冷冻精液中精子形态计量亚群的存在和分布，并确定在每个个体公羊中发现的亚群分布与精子质量之间的关系。主成分分析显示，青年公羊有三个主成分，成年公羊有四个主成分，这两个主成分在两种情况下都代表了超过 84%的累积方差。聚类分析后，青年公羊（CLY）有三个精子形态计量亚群，成年公羊（CLM）有四个，这四个亚群的精子形态具有明确的尺寸和形状。CLY1 包括大、圆、短的精子（37%），CLY2 包括中等大小、略椭圆和细长的精子（48%），CLY3 包括小、长、椭圆和细长的精子（15%）。CLM1 由中等大小和中等椭圆度和伸长率组成（26%），CLM2 由小、长、椭圆和伸长率组成（31%），CLM3 由小和圆组成（32%），CLM4 由大、短和圆组成（8%）。在四个被测试的青年公羊的精液中，三个亚群的分布（P < 0.001）以及精子浓度、总活力（%）、精子活力（%）和整体活力（P < 0.05）均有显著差异。在四个被测试的成年公羊的精液中，四个亚群和不同的精子质量参数也有相同的结果。总之，冷冻保存的公羊精液在精子形态计量亚群方面表现出特定的结构。此外，这些亚群的分布似乎与公羊的成熟年龄和精液质量有关，而精液质量是精子功能的一个非常重要的指标。因此，分析精子形态计量亚群结构与功能测试相结合，可以为评估公羊精子的抗冷冻性提供有价值的信息。
