Department of Animal and Rangeland Sciences, Oregon State University, Corvallis 97331, USA.
J Anim Sci. 2013 Feb;91(2):523-9. doi: 10.2527/jas.2012-5681. Epub 2012 Oct 16.
Rooster semen is an effluent from paired reproductive tracts. Each tract includes a testis, epididymis, and deferent duct. Upon ejaculation, efficacy of sperm propulsion varies among roosters. This phenotype is sperm mobility, that is, the movement of sperm against resistance at body temperature. The present work 1) compares reproductive tract throughput between lines of chickens selected for low and high sperm mobility, 2) demonstrates how semen quality can be defined in terms of an interaction between reproductive tract throughput and the proportion of mobile sperm ejaculated, 3) confirms that phenotype can be linked to genomewide differences in SNPlotype, and 4) shows how breeding can affect semen quality. Sperm mobility phenotype distributions were based on the average of duplicate observations per male (n = 241 and 262 roosters for low and high lines, respectively). Distributions were skewed and normal for low and high lines, respectively. Subsequent analyses used these base populations as sources for test subjects. In the first analysis, 10 males were selected from the mode of each distribution, and sperm mobility data were evaluated by nested ANOVA. Variation was observed between lines (P < 0.0001) but not among males within lines (P = 0.980). Sperm mobility data along with data from paired reproductive tracts were used to estimate combined reproductive tract throughput. Whereas testicular output was 1.2-fold greater in the low line (P = 0.037), the output of mobile sperm per day was 10.5-fold greater in the high line (P < 0.0001). Deferent duct transit differed between tails of the low line (P < 0.0001) but not between the tails of the high line (P = 0.514). Males from the mode and upper tail of the low line were SNPlotyped using a 60k chip by DNA Landmarks. These test subjects were used to associate phenotype with SNPlotype because founder effects and genetic drift could be discounted. Loci of interest were found on multiple chromosomes. Loci on chromosome Z were of particular interest because roosters are homozygous for this sex chromosome and a pronounced maternal effect was observed in a prior heritability study. Midrange phenotypes were produced by crossing low and high sperm mobility lines. Our experimental outcomes demonstrate that genes affect reproductive tract function as well as sperm cell attributes and thereby make semen quality subject to genetic selection.
公鸡精液是由成对的生殖道排出的。每个生殖道包括一个睾丸、附睾和输精管。射精时，公鸡的精子推进力效率不同。这种表型是精子的运动能力，即精子在体温下抵抗阻力的运动能力。本研究 1）比较了选择精子运动能力低和高的鸡的生殖道吞吐量，2）证明了精液质量可以根据生殖道吞吐量与射出的运动精子比例之间的相互作用来定义，3）证实了表型可以与全基因组 SNP 型的差异相关联，4）表明了选育如何影响精液质量。精子运动能力表型分布是基于每个雄性的重复观察平均值（低线和高线分别为 241 只和 262 只公鸡）。分布分别为低线和高线的偏态和正态。随后的分析使用这些基础群体作为试验对象的来源。在第一次分析中，从每个分布的模式中选择了 10 只雄性，通过嵌套 ANOVA 评估精子运动能力数据。在线之间观察到变异（P < 0.0001），但在线内的雄性之间没有变异（P = 0.980）。精子运动能力数据与配对生殖道数据一起用于估计综合生殖道吞吐量。虽然低线的睾丸输出量增加了 1.2 倍（P = 0.037），但高线的每日运动精子输出量增加了 10.5 倍（P < 0.0001）。低线的输精管转运量在尾部之间存在差异（P < 0.0001），但在高线的尾部之间没有差异（P = 0.514）。使用 DNA Landmarks 的 60k 芯片对低线模式和上尾部的雄性进行了 SNP 分型。由于可以排除创始效应和遗传漂变，因此使用这些试验对象将表型与 SNP 型相关联。在多个染色体上发现了感兴趣的位点。Z 染色体上的位点特别有趣，因为公鸡在这条性染色体上是纯合的，在前一项遗传力研究中观察到了明显的母性效应。中程表型是通过杂交低线和高线精子运动能力系产生的。我们的实验结果表明，基因影响生殖道功能以及精子细胞属性，从而使精液质量受到遗传选择的影响。
