Particle distribution in low-volume capillary-loaded chambers

Abstract

Accurate determination of sperm concentration in fluid suspension is a critical component in a semen analysis. Inaccurate estimations can lead to misinterpretation of the spermiogram and, in the case of livestock production, can lead to faulty insemination doses, which can adversely affect stud power, fertility, fecundity, and cost effectiveness of breeding programs. Capillary-loaded slides, like the hemacytometer, have been the standard for calibration of other concentration estimation modalities such as photometry, Coulter counter, flow cytometry, and computer-automated semen analysis (CASA). Single-use capillary-loaded slides, much smaller than the hemacytometer, are frequently used by many of the current CASA systems. As the use of CASA increases, more field reports are suggesting differences between CASA results and hemacytometry. In this article, we establish that these differences are, in large part, due to the Segre-Silberberg effect, which occurs during Poiseuille flow in high-gradient fluid flow in thin capillary-loaded slides. We develop the theory of this phenomenon and derive the scaling and significance of the effect. Finally, we graphically provide a means for predicting the necessary compensation factor when using capillary-loaded slides to determine sperm concentration.